/*! 
 * LESS - Leaner CSS v1.6.1 
 * http://lesscss.org 
 * 
 * Copyright (c) 2009-2014, Alexis Sellier <self@cloudhead.net> 
 * Licensed under the Apache v2 License. 
 * 
 */ 

 /** * @license Apache v2
 */ 



(function (window, undefined) {//
// Stub out `require` in the browser
//
function require(arg) {
    return window.less[arg.split('/')[1]];
};


if (typeof(window.less) === 'undefined' || typeof(window.less.nodeType) !== 'undefined') { window.less = {}; }
less = window.less;
tree = window.less.tree = {};
less.mode = 'browser';

var less, tree;

// Node.js does not have a header file added which defines less
if (less === undefined) {
    less = exports;
    tree = require('./tree');
    less.mode = 'node';
}
//
// less.js - parser
//
//    A relatively straight-forward predictive parser.
//    There is no tokenization/lexing stage, the input is parsed
//    in one sweep.
//
//    To make the parser fast enough to run in the browser, several
//    optimization had to be made:
//
//    - Matching and slicing on a huge input is often cause of slowdowns.
//      The solution is to chunkify the input into smaller strings.
//      The chunks are stored in the `chunks` var,
//      `j` holds the current chunk index, and `currentPos` holds
//      the index of the current chunk in relation to `input`.
//      This gives us an almost 4x speed-up.
//
//    - In many cases, we don't need to match individual tokens;
//      for example, if a value doesn't hold any variables, operations
//      or dynamic references, the parser can effectively 'skip' it,
//      treating it as a literal.
//      An example would be '1px solid #000' - which evaluates to itself,
//      we don't need to know what the individual components are.
//      The drawback, of course is that you don't get the benefits of
//      syntax-checking on the CSS. This gives us a 50% speed-up in the parser,
//      and a smaller speed-up in the code-gen.
//
//
//    Token matching is done with the `$` function, which either takes
//    a terminal string or regexp, or a non-terminal function to call.
//    It also takes care of moving all the indices forwards.
//
//
less.Parser = function Parser(env) {
    var input,       // LeSS input string
        i,           // current index in `input`
        j,           // current chunk
        temp,        // temporarily holds a chunk's state, for backtracking
        memo,        // temporarily holds `i`, when backtracking
        furthest,    // furthest index the parser has gone to
        chunks,      // chunkified input
        current,     // current chunk
        currentPos,  // index of current chunk, in `input`
        parser,
        parsers,
        rootFilename = env && env.filename;

    // Top parser on an import tree must be sure there is one "env"
    // which will then be passed around by reference.
    if (!(env instanceof tree.parseEnv)) {
        env = new tree.parseEnv(env);
    }

    var imports = this.imports = {
        paths: env.paths || [],  // Search paths, when importing
        queue: [],               // Files which haven't been imported yet
        files: env.files,        // Holds the imported parse trees
        contents: env.contents,  // Holds the imported file contents
        contentsIgnoredChars: env.contentsIgnoredChars, // lines inserted, not in the original less
        mime:  env.mime,         // MIME type of .less files
        error: null,             // Error in parsing/evaluating an import
        push: function (path, currentFileInfo, importOptions, callback) {
            var parserImports = this;
            this.queue.push(path);

            var fileParsedFunc = function (e, root, fullPath) {
                parserImports.queue.splice(parserImports.queue.indexOf(path), 1); // Remove the path from the queue

                var importedPreviously = fullPath in parserImports.files || fullPath === rootFilename;

                parserImports.files[fullPath] = root;                        // Store the root

                if (e && !parserImports.error) { parserImports.error = e; }

                callback(e, root, importedPreviously, fullPath);
            };

            if (less.Parser.importer) {
                less.Parser.importer(path, currentFileInfo, fileParsedFunc, env);
            } else {
                less.Parser.fileLoader(path, currentFileInfo, function(e, contents, fullPath, newFileInfo) {
                    if (e) {fileParsedFunc(e); return;}

                    var newEnv = new tree.parseEnv(env);

                    newEnv.currentFileInfo = newFileInfo;
                    newEnv.processImports = false;
                    newEnv.contents[fullPath] = contents;

                    if (currentFileInfo.reference || importOptions.reference) {
                        newFileInfo.reference = true;
                    }

                    if (importOptions.inline) {
                        fileParsedFunc(null, contents, fullPath);
                    } else {
                        new(less.Parser)(newEnv).parse(contents, function (e, root) {
                            fileParsedFunc(e, root, fullPath);
                        });
                    }
                }, env);
            }
        }
    };

    function save()    { temp = current; memo = currentPos = i; }
    function restore() { current = temp; currentPos = i = memo; }

    function sync() {
        if (i > currentPos) {
            current = current.slice(i - currentPos);
            currentPos = i;
        }
    }
    function isWhitespace(str, pos) {
        var code = str.charCodeAt(pos | 0);
        return (code <= 32) && (code === 32 || code === 10 || code === 9);
    }
    //
    // Parse from a token, regexp or string, and move forward if match
    //
    function $(tok) {
        var tokType = typeof tok,
            match, length;

        // Either match a single character in the input,
        // or match a regexp in the current chunk (`current`).
        //
        if (tokType === "string") {
            if (input.charAt(i) !== tok) {
                return null;
            }
            skipWhitespace(1);
            return tok;
        }

        // regexp
        sync ();
        if (! (match = tok.exec(current))) {
            return null;
        }

        length = match[0].length;

        // The match is confirmed, add the match length to `i`,
        // and consume any extra white-space characters (' ' || '\n')
        // which come after that. The reason for this is that LeSS's
        // grammar is mostly white-space insensitive.
        //
        skipWhitespace(length);

        if(typeof(match) === 'string') {
            return match;
        } else {
            return match.length === 1 ? match[0] : match;
        }
    }

    // Specialization of $(tok)
    function $re(tok) {
        if (i > currentPos) {
            current = current.slice(i - currentPos);
            currentPos = i;
        }
        var m = tok.exec(current);
        if (!m) {
            return null;
        }

        skipWhitespace(m[0].length);
        if(typeof m === "string") {
            return m;
        }

        return m.length === 1 ? m[0] : m;
    }

    var _$re = $re;

    // Specialization of $(tok)
    function $char(tok) {
        if (input.charAt(i) !== tok) {
            return null;
        }
        skipWhitespace(1);
        return tok;
    }

    function skipWhitespace(length) {
        var oldi = i, oldj = j,
            curr = i - currentPos,
            endIndex = i + current.length - curr,
            mem = (i += length),
            inp = input,
            c;

        for (; i < endIndex; i++) {
            c = inp.charCodeAt(i);
            if (c > 32) {
                break;
            }

            if ((c !== 32) && (c !== 10) && (c !== 9) && (c !== 13)) {
                break;
            }
         }

        current = current.slice(length + i - mem + curr);
        currentPos = i;

        if (!current.length && (j < chunks.length - 1)) {
            current = chunks[++j];
        }

        return oldi !== i || oldj !== j;
    }

    function expect(arg, msg) {
        // some older browsers return typeof 'function' for RegExp
        var result = (Object.prototype.toString.call(arg) === '[object Function]') ? arg.call(parsers) : $(arg);
        if (result) {
            return result;
        }
        error(msg || (typeof(arg) === 'string' ? "expected '" + arg + "' got '" + input.charAt(i) + "'"
                                               : "unexpected token"));
    }

    // Specialization of expect()
    function expectChar(arg, msg) {
        if (input.charAt(i) === arg) {
            skipWhitespace(1);
            return arg;
        }
        error(msg || "expected '" + arg + "' got '" + input.charAt(i) + "'");
    }

    function error(msg, type) {
        var e = new Error(msg);
        e.index = i;
        e.type = type || 'Syntax';
        throw e;
    }

    // Same as $(), but don't change the state of the parser,
    // just return the match.
    function peek(tok) {
        if (typeof(tok) === 'string') {
            return input.charAt(i) === tok;
        } else {
            return tok.test(current);
        }
    }

    // Specialization of peek()
    function peekChar(tok) {
        return input.charAt(i) === tok;
    }


    function getInput(e, env) {
        if (e.filename && env.currentFileInfo.filename && (e.filename !== env.currentFileInfo.filename)) {
            return parser.imports.contents[e.filename];
        } else {
            return input;
        }
    }

    function getLocation(index, inputStream) {
        var n = index + 1,
            line = null,
            column = -1;

        while (--n >= 0 && inputStream.charAt(n) !== '\n') {
            column++;
        }

        if (typeof index === 'number') {
            line = (inputStream.slice(0, index).match(/\n/g) || "").length;
        }

        return {
            line: line,
            column: column
        };
    }

    function getDebugInfo(index, inputStream, env) {
        var filename = env.currentFileInfo.filename;
        if(less.mode !== 'browser' && less.mode !== 'rhino') {
            filename = require('path').resolve(filename);
        }

        return {
            lineNumber: getLocation(index, inputStream).line + 1,
            fileName: filename
        };
    }

    function LessError(e, env) {
        var input = getInput(e, env),
            loc = getLocation(e.index, input),
            line = loc.line,
            col  = loc.column,
            callLine = e.call && getLocation(e.call, input).line,
            lines = input.split('\n');

        this.type = e.type || 'Syntax';
        this.message = e.message;
        this.filename = e.filename || env.currentFileInfo.filename;
        this.index = e.index;
        this.line = typeof(line) === 'number' ? line + 1 : null;
        this.callLine = callLine + 1;
        this.callExtract = lines[callLine];
        this.stack = e.stack;
        this.column = col;
        this.extract = [
            lines[line - 1],
            lines[line],
            lines[line + 1]
        ];
    }

    LessError.prototype = new Error();
    LessError.prototype.constructor = LessError;

    this.env = env = env || {};

    // The optimization level dictates the thoroughness of the parser,
    // the lower the number, the less nodes it will create in the tree.
    // This could matter for debugging, or if you want to access
    // the individual nodes in the tree.
    this.optimization = ('optimization' in this.env) ? this.env.optimization : 1;

    //
    // The Parser
    //
    parser = {

        imports: imports,
        //
        // Parse an input string into an abstract syntax tree,
        // @param str A string containing 'less' markup
        // @param callback call `callback` when done.
        // @param [additionalData] An optional map which can contains vars - a map (key, value) of variables to apply
        //
        parse: function (str, callback, additionalData) {
            var root, line, lines, error = null, globalVars, modifyVars, preText = "";

            i = j = currentPos = furthest = 0;

            globalVars = (additionalData && additionalData.globalVars) ? less.Parser.serializeVars(additionalData.globalVars) + '\n' : '';
            modifyVars = (additionalData && additionalData.modifyVars) ? '\n' + less.Parser.serializeVars(additionalData.modifyVars) : '';

            if (globalVars || (additionalData && additionalData.banner)) {
                preText = ((additionalData && additionalData.banner) ? additionalData.banner : "") + globalVars;
                parser.imports.contentsIgnoredChars[env.currentFileInfo.filename] = preText.length;
            }

            str = str.replace(/\r\n/g, '\n');
            // Remove potential UTF Byte Order Mark
            input = str = preText + str.replace(/^\uFEFF/, '') + modifyVars;
            parser.imports.contents[env.currentFileInfo.filename] = str;

            // Split the input into chunks.
            chunks = (function (input) {
                var len = input.length, level = 0, parenLevel = 0,
                    lastOpening, lastClosing, lastMultiComment, lastMultiCommentEndBrace,
                    chunks = [], emitFrom = 0,
                    parserCurrentIndex, currentChunkStartIndex, cc, cc2, matched;

                function fail(msg, index) {
                    error = new(LessError)({
                        index: index || parserCurrentIndex,
                        type: 'Parse',
                        message: msg,
                        filename: env.currentFileInfo.filename
                    }, env);
                }

                function emitChunk(force) {
                    var len = parserCurrentIndex - emitFrom;
                    if (((len < 512) && !force) || !len) {
                        return;
                    }
                    chunks.push(input.slice(emitFrom, parserCurrentIndex + 1));
                    emitFrom = parserCurrentIndex + 1;
                }

                for (parserCurrentIndex = 0; parserCurrentIndex < len; parserCurrentIndex++) {
                    cc = input.charCodeAt(parserCurrentIndex);
                    if (((cc >= 97) && (cc <= 122)) || (cc < 34)) {
                        // a-z or whitespace
                        continue;
                    }

                    switch (cc) {
                        case 40:                        // (
                            parenLevel++; continue;
                        case 41:                        // )
                            parenLevel--; continue;
                        case 59:                        // ;
                            if (!parenLevel) { emitChunk(); }
                            continue;
                        case 123:                       // {
                            level++; lastOpening = parserCurrentIndex; continue;
                        case 125:                       // }
                            level--; lastClosing = parserCurrentIndex;
                            if (!level) { emitChunk(); }
                            continue;
                        case 92:                        // \
                            if (parserCurrentIndex < len - 1) { parserCurrentIndex++; continue; }
                            return fail("unescaped `\\`");
                        case 34:
                        case 39:
                        case 96:                        // ", ' and `
                            matched = 0;
                            currentChunkStartIndex = parserCurrentIndex;
                            for (parserCurrentIndex = parserCurrentIndex + 1; parserCurrentIndex < len; parserCurrentIndex++) {
                                cc2 = input.charCodeAt(parserCurrentIndex);
                                if (cc2 > 96) { continue; }
                                if (cc2 == cc) { matched = 1; break; }
                                if (cc2 == 92) {        // \
                                    if (parserCurrentIndex == len - 1) {
                                        return fail("unescaped `\\`");
                                    }
                                    parserCurrentIndex++;
                                }
                            }
                            if (matched) { continue; }
                            return fail("unmatched `" + String.fromCharCode(cc) + "`", currentChunkStartIndex);
                        case 47:                        // /, check for comment
                            if (parenLevel || (parserCurrentIndex == len - 1)) { continue; }
                            cc2 = input.charCodeAt(parserCurrentIndex + 1);
                            if (cc2 == 47) {
                                // //, find lnfeed
                                for (parserCurrentIndex = parserCurrentIndex + 2; parserCurrentIndex < len; parserCurrentIndex++) {
                                    cc2 = input.charCodeAt(parserCurrentIndex);
                                    if ((cc2 <= 13) && ((cc2 == 10) || (cc2 == 13))) { break; }
                                }
                            } else if (cc2 == 42) {
                                // /*, find */
                                lastMultiComment = currentChunkStartIndex = parserCurrentIndex;
                                for (parserCurrentIndex = parserCurrentIndex + 2; parserCurrentIndex < len - 1; parserCurrentIndex++) {
                                    cc2 = input.charCodeAt(parserCurrentIndex);
                                    if (cc2 == 125) { lastMultiCommentEndBrace = parserCurrentIndex; }
                                    if (cc2 != 42) { continue; }
                                    if (input.charCodeAt(parserCurrentIndex + 1) == 47) { break; }
                                }
                                if (parserCurrentIndex == len - 1) {
                                    return fail("missing closing `*/`", currentChunkStartIndex);
                                }
                            }
                            continue;
                        case 42:                       // *, check for unmatched */
                            if ((parserCurrentIndex < len - 1) && (input.charCodeAt(parserCurrentIndex + 1) == 47)) {
                                return fail("unmatched `/*`");
                            }
                            continue;
                    }
                }

                if (level !== 0) {
                    if (level > 0) {
                        if ((lastMultiComment > lastOpening) && (lastMultiCommentEndBrace > lastMultiComment)) {
                            return fail("missing closing `}` or `*/`", lastOpening);
                        } else {
                            return fail("missing closing `}`", lastOpening);
                        }
                    }
                    return fail("missing opening `{`", lastClosing);
                } else if (parenLevel !== 0) {
                    return fail((parenLevel > 0) ? "missing closing `)`" : "missing opening `(`");
                }

                emitChunk(true);
                return chunks;
            })(str);

            if (error) {
                return callback(new(LessError)(error, env));
            }

            current = chunks[0];

            // Start with the primary rule.
            // The whole syntax tree is held under a Ruleset node,
            // with the `root` property set to true, so no `{}` are
            // output. The callback is called when the input is parsed.
            try {
                root = new(tree.Ruleset)(null, this.parsers.primary());
                root.root = true;
                root.firstRoot = true;
            } catch (e) {
                return callback(new(LessError)(e, env));
            }

            root.toCSS = (function (evaluate) {
                return function (options, variables) {
                    options = options || {};
                    var evaldRoot,
                        css,
                        evalEnv = new tree.evalEnv(options);
                        
                    //
                    // Allows setting variables with a hash, so:
                    //
                    //   `{ color: new(tree.Color)('#f01') }` will become:
                    //
                    //   new(tree.Rule)('@color',
                    //     new(tree.Value)([
                    //       new(tree.Expression)([
                    //         new(tree.Color)('#f01')
                    //       ])
                    //     ])
                    //   )
                    //
                    if (typeof(variables) === 'object' && !Array.isArray(variables)) {
                        variables = Object.keys(variables).map(function (k) {
                            var value = variables[k];

                            if (! (value instanceof tree.Value)) {
                                if (! (value instanceof tree.Expression)) {
                                    value = new(tree.Expression)([value]);
                                }
                                value = new(tree.Value)([value]);
                            }
                            return new(tree.Rule)('@' + k, value, false, null, 0);
                        });
                        evalEnv.frames = [new(tree.Ruleset)(null, variables)];
                    }

                    try {
                        var preEvalVisitors = [],
                            visitors = [
                                new(tree.joinSelectorVisitor)(),
                                new(tree.processExtendsVisitor)(),
                                new(tree.toCSSVisitor)({compress: Boolean(options.compress)})
                            ], i, root = this;

                        if (options.plugins) {
                            for(i =0; i < options.plugins.length; i++) {
                                if (options.plugins[i].isPreEvalVisitor) {
                                    preEvalVisitors.push(options.plugins[i]);
                                } else {
                                    if (options.plugins[i].isPreVisitor) {
                                        visitors.splice(0, 0, options.plugins[i]);
                                    } else {
                                        visitors.push(options.plugins[i]);
                                    }
                                }
                            }
                        }

                        for(i = 0; i < preEvalVisitors.length; i++) {
                            preEvalVisitors[i].run(root);
                        }

                        evaldRoot = evaluate.call(root, evalEnv);

                        for(i = 0; i < visitors.length; i++) {
                            visitors[i].run(evaldRoot);
                        }

                        if (options.sourceMap) {
                            evaldRoot = new tree.sourceMapOutput(
                                {
                                    contentsIgnoredCharsMap: parser.imports.contentsIgnoredChars,
                                    writeSourceMap: options.writeSourceMap,
                                    rootNode: evaldRoot,
                                    contentsMap: parser.imports.contents,
                                    sourceMapFilename: options.sourceMapFilename,
                                    sourceMapURL: options.sourceMapURL,
                                    outputFilename: options.sourceMapOutputFilename,
                                    sourceMapBasepath: options.sourceMapBasepath,
                                    sourceMapRootpath: options.sourceMapRootpath,
                                    outputSourceFiles: options.outputSourceFiles,
                                    sourceMapGenerator: options.sourceMapGenerator
                                });
                        }

                        css = evaldRoot.toCSS({
                                compress: Boolean(options.compress),
                                dumpLineNumbers: env.dumpLineNumbers,
                                strictUnits: Boolean(options.strictUnits)});
                    } catch (e) {
                        throw new(LessError)(e, env);
                    }

                    if (options.cleancss && less.mode === 'node') {
                        var CleanCSS = require('clean-css'),
                            cleancssOptions = options.cleancssOptions || {};

                        if (cleancssOptions.keepSpecialComments === undefined) {
                            cleancssOptions.keepSpecialComments = "*";
                        }
                        cleancssOptions.processImport = false;
                        cleancssOptions.noRebase = true;
                        if (cleancssOptions.noAdvanced === undefined) {
                            cleancssOptions.noAdvanced = true;
                        }

                        return new CleanCSS(cleancssOptions).minify(css);
                    } else if (options.compress) {
                        return css.replace(/(^(\s)+)|((\s)+$)/g, "");
                    } else {
                        return css;
                    }
                };
            })(root.eval);

            // If `i` is smaller than the `input.length - 1`,
            // it means the parser wasn't able to parse the whole
            // string, so we've got a parsing error.
            //
            // We try to extract a \n delimited string,
            // showing the line where the parse error occured.
            // We split it up into two parts (the part which parsed,
            // and the part which didn't), so we can color them differently.
            if (i < input.length - 1) {
                i = furthest;
                var loc = getLocation(i, input);
                lines = input.split('\n');
                line = loc.line + 1;

                error = {
                    type: "Parse",
                    message: "Unrecognised input",
                    index: i,
                    filename: env.currentFileInfo.filename,
                    line: line,
                    column: loc.column,
                    extract: [
                        lines[line - 2],
                        lines[line - 1],
                        lines[line]
                    ]
                };
            }

            var finish = function (e) {
                e = error || e || parser.imports.error;

                if (e) {
                    if (!(e instanceof LessError)) {
                        e = new(LessError)(e, env);
                    }

                    return callback(e);
                }
                else {
                    return callback(null, root);
                }
            };

            if (env.processImports !== false) {
                new tree.importVisitor(this.imports, finish)
                    .run(root);
            } else {
                return finish();
            }
        },

        //
        // Here in, the parsing rules/functions
        //
        // The basic structure of the syntax tree generated is as follows:
        //
        //   Ruleset ->  Rule -> Value -> Expression -> Entity
        //
        // Here's some LESS code:
        //
        //    .class {
        //      color: #fff;
        //      border: 1px solid #000;
        //      width: @w + 4px;
        //      > .child {...}
        //    }
        //
        // And here's what the parse tree might look like:
        //
        //     Ruleset (Selector '.class', [
        //         Rule ("color",  Value ([Expression [Color #fff]]))
        //         Rule ("border", Value ([Expression [Dimension 1px][Keyword "solid"][Color #000]]))
        //         Rule ("width",  Value ([Expression [Operation "+" [Variable "@w"][Dimension 4px]]]))
        //         Ruleset (Selector [Element '>', '.child'], [...])
        //     ])
        //
        //  In general, most rules will try to parse a token with the `$()` function, and if the return
        //  value is truly, will return a new node, of the relevant type. Sometimes, we need to check
        //  first, before parsing, that's when we use `peek()`.
        //
        parsers: parsers = {
            //
            // The `primary` rule is the *entry* and *exit* point of the parser.
            // The rules here can appear at any level of the parse tree.
            //
            // The recursive nature of the grammar is an interplay between the `block`
            // rule, which represents `{ ... }`, the `ruleset` rule, and this `primary` rule,
            // as represented by this simplified grammar:
            //
            //     primary  →  (ruleset | rule)+
            //     ruleset  →  selector+ block
            //     block    →  '{' primary '}'
            //
            // Only at one point is the primary rule not called from the
            // block rule: at the root level.
            //
            primary: function () {
                var mixin = this.mixin, $re = _$re, root = [], node;

                while (current)
                {
                    node = this.extendRule() || mixin.definition() || this.rule() || this.ruleset() ||
                        mixin.call() || this.comment() || this.directive();
                    if (node) {
                        root.push(node);
                    } else {
                        if (!($re(/^[\s\n]+/) || $re(/^;+/))) {
                            break;
                        }
                    }
                }

                return root;
            },

            // We create a Comment node for CSS comments `/* */`,
            // but keep the LeSS comments `//` silent, by just skipping
            // over them.
            comment: function () {
                var comment;

                if (input.charAt(i) !== '/') { return; }

                if (input.charAt(i + 1) === '/') {
                    return new(tree.Comment)($re(/^\/\/.*/), true, i, env.currentFileInfo);
                }
                comment = $re(/^\/\*(?:[^*]|\*+[^\/*])*\*+\/\n?/);
                if (comment) {
                    return new(tree.Comment)(comment, false, i, env.currentFileInfo);
                }
            },

            comments: function () {
                var comment, comments = [];

                while(true) {
                    comment = this.comment();
                    if (!comment) {
                        break;
                    }
                    comments.push(comment);
                }

                return comments;
            },

            //
            // Entities are tokens which can be found inside an Expression
            //
            entities: {
                //
                // A string, which supports escaping " and '
                //
                //     "milky way" 'he\'s the one!'
                //
                quoted: function () {
                    var str, j = i, e, index = i;

                    if (input.charAt(j) === '~') { j++; e = true; } // Escaped strings
                    if (input.charAt(j) !== '"' && input.charAt(j) !== "'") { return; }

                    if (e) { $char('~'); }

                    str = $re(/^"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'/);
                    if (str) {
                        return new(tree.Quoted)(str[0], str[1] || str[2], e, index, env.currentFileInfo);
                    }
                },

                //
                // A catch-all word, such as:
                //
                //     black border-collapse
                //
                keyword: function () {
                    var k;

                    k = $re(/^[_A-Za-z-][_A-Za-z0-9-]*/);
                    if (k) {
                        var color = tree.Color.fromKeyword(k);
                        if (color) {
                            return color;
                        }
                        return new(tree.Keyword)(k);
                    }
                },

                //
                // A function call
                //
                //     rgb(255, 0, 255)
                //
                // We also try to catch IE's `alpha()`, but let the `alpha` parser
                // deal with the details.
                //
                // The arguments are parsed with the `entities.arguments` parser.
                //
                call: function () {
                    var name, nameLC, args, alpha_ret, index = i;

                    name = /^([\w-]+|%|progid:[\w\.]+)\(/.exec(current);
                    if (!name) { return; }

                    name = name[1];
                    nameLC = name.toLowerCase();
                    if (nameLC === 'url') {
                        return null;
                    }

                    i += name.length;

                    if (nameLC === 'alpha') {
                        alpha_ret = parsers.alpha();
                        if(typeof alpha_ret !== 'undefined') {
                            return alpha_ret;
                        }
                    }

                    $char('('); // Parse the '(' and consume whitespace.

                    args = this.arguments();

                    if (! $char(')')) {
                        return;
                    }

                    if (name) { return new(tree.Call)(name, args, index, env.currentFileInfo); }
                },
                arguments: function () {
                    var args = [], arg;

                    while (true) {
                        arg = this.assignment() || parsers.expression();
                        if (!arg) {
                            break;
                        }
                        args.push(arg);
                        if (! $char(',')) {
                            break;
                        }
                    }
                    return args;
                },
                literal: function () {
                    return this.dimension() ||
                           this.color() ||
                           this.quoted() ||
                           this.unicodeDescriptor();
                },

                // Assignments are argument entities for calls.
                // They are present in ie filter properties as shown below.
                //
                //     filter: progid:DXImageTransform.Microsoft.Alpha( *opacity=50* )
                //

                assignment: function () {
                    var key, value;
                    key = $re(/^\w+(?=\s?=)/i);
                    if (!key) {
                        return;
                    }
                    if (!$char('=')) {
                        return;
                    }
                    value = parsers.entity();
                    if (value) {
                        return new(tree.Assignment)(key, value);
                    }
                },

                //
                // Parse url() tokens
                //
                // We use a specific rule for urls, because they don't really behave like
                // standard function calls. The difference is that the argument doesn't have
                // to be enclosed within a string, so it can't be parsed as an Expression.
                //
                url: function () {
                    var value;

                    if (input.charAt(i) !== 'u' || !$re(/^url\(/)) {
                        return;
                    }

                    value = this.quoted() || this.variable() ||
                            $re(/^(?:(?:\\[\(\)'"])|[^\(\)'"])+/) || "";

                    expectChar(')');

                    return new(tree.URL)((value.value != null || value instanceof tree.Variable)
                                        ? value : new(tree.Anonymous)(value), env.currentFileInfo);
                },

                //
                // A Variable entity, such as `@fink`, in
                //
                //     width: @fink + 2px
                //
                // We use a different parser for variable definitions,
                // see `parsers.variable`.
                //
                variable: function () {
                    var name, index = i;

                    if (input.charAt(i) === '@' && (name = $re(/^@@?[\w-]+/))) {
                        return new(tree.Variable)(name, index, env.currentFileInfo);
                    }
                },

                // A variable entity useing the protective {} e.g. @{var}
                variableCurly: function () {
                    var curly, index = i;

                    if (input.charAt(i) === '@' && (curly = $re(/^@\{([\w-]+)\}/))) {
                        return new(tree.Variable)("@" + curly[1], index, env.currentFileInfo);
                    }
                },

                //
                // A Hexadecimal color
                //
                //     #4F3C2F
                //
                // `rgb` and `hsl` colors are parsed through the `entities.call` parser.
                //
                color: function () {
                    var rgb;

                    if (input.charAt(i) === '#' && (rgb = $re(/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/))) {
                        return new(tree.Color)(rgb[1]);
                    }
                },

                //
                // A Dimension, that is, a number and a unit
                //
                //     0.5em 95%
                //
                dimension: function () {
                    var value, c = input.charCodeAt(i);
                    //Is the first char of the dimension 0-9, '.', '+' or '-'
                    if ((c > 57 || c < 43) || c === 47 || c == 44) {
                        return;
                    }

                    value = $re(/^([+-]?\d*\.?\d+)(%|[a-z]+)?/);
                    if (value) {
                        return new(tree.Dimension)(value[1], value[2]);
                    }
                },

                //
                // A unicode descriptor, as is used in unicode-range
                //
                // U+0??  or U+00A1-00A9
                //
                unicodeDescriptor: function () {
                    var ud;

                    ud = $re(/^U\+[0-9a-fA-F?]+(\-[0-9a-fA-F?]+)?/);
                    if (ud) {
                        return new(tree.UnicodeDescriptor)(ud[0]);
                    }
                },

                //
                // JavaScript code to be evaluated
                //
                //     `window.location.href`
                //
                javascript: function () {
                    var str, j = i, e;

                    if (input.charAt(j) === '~') { j++; e = true; } // Escaped strings
                    if (input.charAt(j) !== '`') { return; }
                    if (env.javascriptEnabled !== undefined && !env.javascriptEnabled) {
                        error("You are using JavaScript, which has been disabled.");
                    }

                    if (e) { $char('~'); }

                    str = $re(/^`([^`]*)`/);
                    if (str) {
                        return new(tree.JavaScript)(str[1], i, e);
                    }
                }
            },

            //
            // The variable part of a variable definition. Used in the `rule` parser
            //
            //     @fink:
            //
            variable: function () {
                var name;

                if (input.charAt(i) === '@' && (name = $re(/^(@[\w-]+)\s*:/))) { return name[1]; }
            },

            //
            // extend syntax - used to extend selectors
            //
            extend: function(isRule) {
                var elements, e, index = i, option, extendList, extend;

                if (!(isRule ? $re(/^&:extend\(/) : $re(/^:extend\(/))) { return; }

                do {
                    option = null;
                    elements = null;
                    while (! (option = $re(/^(all)(?=\s*(\)|,))/))) {
                        e = this.element();
                        if (!e) { break; }
                        if (elements) { elements.push(e); } else { elements = [ e ]; }
                    }

                    option = option && option[1];

                    extend = new(tree.Extend)(new(tree.Selector)(elements), option, index);
                    if (extendList) { extendList.push(extend); } else { extendList = [ extend ]; }

                } while($char(","));
                
                expect(/^\)/);

                if (isRule) {
                    expect(/^;/);
                }

                return extendList;
            },

            //
            // extendRule - used in a rule to extend all the parent selectors
            //
            extendRule: function() {
                return this.extend(true);
            },
            
            //
            // Mixins
            //
            mixin: {
                //
                // A Mixin call, with an optional argument list
                //
                //     #mixins > .square(#fff);
                //     .rounded(4px, black);
                //     .button;
                //
                // The `while` loop is there because mixins can be
                // namespaced, but we only support the child and descendant
                // selector for now.
                //
                call: function () {
                    var s = input.charAt(i), important = false, index = i, elemIndex,
                        elements, elem, e, c, args;

                    if (s !== '.' && s !== '#') { return; }

                    save(); // stop us absorbing part of an invalid selector

                    while (true) {
                        elemIndex = i;
                        e = $re(/^[#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/);
                        if (!e) {
                            break;
                        }
                        elem = new(tree.Element)(c, e, elemIndex, env.currentFileInfo);
                        if (elements) { elements.push(elem); } else { elements = [ elem ]; }
                        c = $char('>');
                    }
                    if ($char('(')) {
                        args = this.args(true).args;
                        expectChar(')');
                    }

                    if (parsers.important()) {
                        important = true;
                    }

                    if (elements && ($char(';') || peekChar('}'))) {
                        return new(tree.mixin.Call)(elements, args, index, env.currentFileInfo, important);
                    }

                    restore();
                },
                args: function (isCall) {
                    var parsers = parser.parsers, entities = parsers.entities,
                        returner = { args:null, variadic: false },
                        expressions = [], argsSemiColon = [], argsComma = [],
                        isSemiColonSeperated, expressionContainsNamed, name, nameLoop, value, arg;

                    while (true) {
                        if (isCall) {
                            arg = parsers.expression();
                        } else {
                            parsers.comments();
                            if (input.charAt(i) === '.' && $re(/^\.{3}/)) {
                                returner.variadic = true;
                                if ($char(";") && !isSemiColonSeperated) {
                                    isSemiColonSeperated = true;
                                }
                                (isSemiColonSeperated ? argsSemiColon : argsComma)
                                    .push({ variadic: true });
                                break;
                            }
                            arg = entities.variable() || entities.literal() || entities.keyword();
                        }

                        if (!arg) {
                            break;
                        }

                        nameLoop = null;
                        if (arg.throwAwayComments) {
                            arg.throwAwayComments();
                        }
                        value = arg;
                        var val = null;

                        if (isCall) {
                            // Variable
                            if (arg.value.length == 1) {
                                val = arg.value[0];
                            }
                        } else {
                            val = arg;
                        }

                        if (val && val instanceof tree.Variable) {
                            if ($char(':')) {
                                if (expressions.length > 0) {
                                    if (isSemiColonSeperated) {
                                        error("Cannot mix ; and , as delimiter types");
                                    }
                                    expressionContainsNamed = true;
                                }
                                value = expect(parsers.expression);
                                nameLoop = (name = val.name);
                            } else if (!isCall && $re(/^\.{3}/)) {
                                returner.variadic = true;
                                if ($char(";") && !isSemiColonSeperated) {
                                    isSemiColonSeperated = true;
                                }
                                (isSemiColonSeperated ? argsSemiColon : argsComma)
                                    .push({ name: arg.name, variadic: true });
                                break;
                            } else if (!isCall) {
                                name = nameLoop = val.name;
                                value = null;
                            }
                        }

                        if (value) {
                            expressions.push(value);
                        }

                        argsComma.push({ name:nameLoop, value:value });

                        if ($char(',')) {
                            continue;
                        }

                        if ($char(';') || isSemiColonSeperated) {

                            if (expressionContainsNamed) {
                                error("Cannot mix ; and , as delimiter types");
                            }

                            isSemiColonSeperated = true;

                            if (expressions.length > 1) {
                                value = new(tree.Value)(expressions);
                            }
                            argsSemiColon.push({ name:name, value:value });

                            name = null;
                            expressions = [];
                            expressionContainsNamed = false;
                        }
                    }

                    returner.args = isSemiColonSeperated ? argsSemiColon : argsComma;
                    return returner;
                },
                //
                // A Mixin definition, with a list of parameters
                //
                //     .rounded (@radius: 2px, @color) {
                //        ...
                //     }
                //
                // Until we have a finer grained state-machine, we have to
                // do a look-ahead, to make sure we don't have a mixin call.
                // See the `rule` function for more information.
                //
                // We start by matching `.rounded (`, and then proceed on to
                // the argument list, which has optional default values.
                // We store the parameters in `params`, with a `value` key,
                // if there is a value, such as in the case of `@radius`.
                //
                // Once we've got our params list, and a closing `)`, we parse
                // the `{...}` block.
                //
                definition: function () {
                    var name, params = [], match, ruleset, cond, variadic = false;
                    if ((input.charAt(i) !== '.' && input.charAt(i) !== '#') ||
                        peek(/^[^{]*\}/)) {
                        return;
                    }

                    save();

                    match = $re(/^([#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+)\s*\(/);
                    if (match) {
                        name = match[1];

                        var argInfo = this.args(false);
                        params = argInfo.args;
                        variadic = argInfo.variadic;

                        // .mixincall("@{a}");
                        // looks a bit like a mixin definition.. so we have to be nice and restore
                        if (!$char(')')) {
                            furthest = i;
                            restore();
                        }
                        
                        parsers.comments();

                        if ($re(/^when/)) { // Guard
                            cond = expect(parsers.conditions, 'expected condition');
                        }

                        ruleset = parsers.block();

                        if (ruleset) {
                            return new(tree.mixin.Definition)(name, params, ruleset, cond, variadic);
                        } else {
                            restore();
                        }
                    }
                }
            },

            //
            // Entities are the smallest recognized token,
            // and can be found inside a rule's value.
            //
            entity: function () {
                var entities = this.entities;

                return entities.literal() || entities.variable() || entities.url() ||
                       entities.call()    || entities.keyword()  || entities.javascript() ||
                       this.comment();
            },

            //
            // A Rule terminator. Note that we use `peek()` to check for '}',
            // because the `block` rule will be expecting it, but we still need to make sure
            // it's there, if ';' was ommitted.
            //
            end: function () {
                return $char(';') || peekChar('}');
            },

            //
            // IE's alpha function
            //
            //     alpha(opacity=88)
            //
            alpha: function () {
                var value;

                if (! $re(/^\(opacity=/i)) { return; }
                value = $re(/^\d+/) || this.entities.variable();
                if (value) {
                    expectChar(')');
                    return new(tree.Alpha)(value);
                }
            },

            //
            // A Selector Element
            //
            //     div
            //     + h1
            //     #socks
            //     input[type="text"]
            //
            // Elements are the building blocks for Selectors,
            // they are made out of a `Combinator` (see combinator rule),
            // and an element name, such as a tag a class, or `*`.
            //
            element: function () {
                var e, c, v, index = i;

                c = this.combinator();

                e = $re(/^(?:\d+\.\d+|\d+)%/) || $re(/^(?:[.#]?|:*)(?:[\w-]|[^\x00-\x9f]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/) ||
                    $char('*') || $char('&') || this.attribute() || $re(/^\([^()@]+\)/) || $re(/^[\.#](?=@)/) ||
                    this.entities.variableCurly();

                if (! e) {
                    if ($char('(')) {
                        if ((v = this.selector()) && $char(')')) {
                            e = new(tree.Paren)(v);
                        }
                    }
                }

                if (e) { return new(tree.Element)(c, e, index, env.currentFileInfo); }
            },

            //
            // Combinators combine elements together, in a Selector.
            //
            // Because our parser isn't white-space sensitive, special care
            // has to be taken, when parsing the descendant combinator, ` `,
            // as it's an empty space. We have to check the previous character
            // in the input, to see if it's a ` ` character. More info on how
            // we deal with this in *combinator.js*.
            //
            combinator: function () {
                var c = input.charAt(i);
                
                if (c === '>' || c === '+' || c === '~' || c === '|' || c === '^') {
                    i++;
                    if (input.charAt(i) === '^') {
                        c = '^^';
                        i++;
                    }
                    while (isWhitespace(input, i)) { i++; }
                    return new(tree.Combinator)(c);
                } else if (isWhitespace(input, i - 1)) {
                    return new(tree.Combinator)(" ");
                } else {
                    return new(tree.Combinator)(null);
                }
            },
            //
            // A CSS selector (see selector below)
            // with less extensions e.g. the ability to extend and guard
            //
            lessSelector: function () {
                return this.selector(true);
            },
            //
            // A CSS Selector
            //
            //     .class > div + h1
            //     li a:hover
            //
            // Selectors are made out of one or more Elements, see above.
            //
            selector: function (isLess) {
                var index = i, $re = _$re, elements, extendList, c, e, extend, when, condition;

                while ((isLess && (extend = this.extend())) || (isLess && (when = $re(/^when/))) || (e = this.element())) {
                    if (when) {
                        condition = expect(this.conditions, 'expected condition');
                    } else if (condition) {
                        error("CSS guard can only be used at the end of selector");
                    } else if (extend) {
                        if (extendList) { extendList.push(extend); } else { extendList = [ extend ]; }
                    } else {
                        if (extendList) { error("Extend can only be used at the end of selector"); }
                        c = input.charAt(i);
                        if (elements) { elements.push(e); } else { elements = [ e ]; }
                        e = null;
                    }
                    if (c === '{' || c === '}' || c === ';' || c === ',' || c === ')') {
                        break;
                    }
                }

                if (elements) { return new(tree.Selector)(elements, extendList, condition, index, env.currentFileInfo); }
                if (extendList) { error("Extend must be used to extend a selector, it cannot be used on its own"); }
            },
            attribute: function () {
                if (! $char('[')) { return; }

                var entities = this.entities,
                    key, val, op;

                if (!(key = entities.variableCurly())) {
                    key = expect(/^(?:[_A-Za-z0-9-\*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
                }

                op = $re(/^[|~*$^]?=/);
                if (op) {
                    val = entities.quoted() || $re(/^[0-9]+%/) || $re(/^[\w-]+/) || entities.variableCurly();
                }

                expectChar(']');

                return new(tree.Attribute)(key, op, val);
            },

            //
            // The `block` rule is used by `ruleset` and `mixin.definition`.
            // It's a wrapper around the `primary` rule, with added `{}`.
            //
            block: function () {
                var content;
                if ($char('{') && (content = this.primary()) && $char('}')) {
                    return content;
                }
            },

            //
            // div, .class, body > p {...}
            //
            ruleset: function () {
                var selectors, s, rules, debugInfo;
                
                save();

                if (env.dumpLineNumbers) {
                    debugInfo = getDebugInfo(i, input, env);
                }

                while (true) {
                    s = this.lessSelector();
                    if (!s) {
                        break;
                    }
                    if (selectors) { selectors.push(s); } else { selectors = [ s ]; }
                    this.comments();
                    if (s.condition && selectors.length > 1) {
                        error("Guards are only currently allowed on a single selector.");
                    }
                    if (! $char(',')) { break; }
                    if (s.condition) {
                        error("Guards are only currently allowed on a single selector.");
                    }
                    this.comments();
                }

                if (selectors && (rules = this.block())) {
                    var ruleset = new(tree.Ruleset)(selectors, rules, env.strictImports);
                    if (env.dumpLineNumbers) {
                        ruleset.debugInfo = debugInfo;
                    }
                    return ruleset;
                } else {
                    // Backtrack
                    furthest = i;
                    restore();
                }
            },
            rule: function (tryAnonymous) {
                var name, value, c = input.charAt(i), important, merge = false;
                save();

                if (c === '.' || c === '#' || c === '&') { return; }

                name = this.variable() || this.ruleProperty();
                if (name) {
                    // prefer to try to parse first if its a variable or we are compressing
                    // but always fallback on the other one
                    value = !tryAnonymous && (env.compress || (name.charAt && (name.charAt(0) === '@'))) ?
                        (this.value() || this.anonymousValue()) :
                        (this.anonymousValue() || this.value());

                    important = this.important();
                    
                    // a name returned by this.ruleProperty() is always an array of the form:
                    // ["", "string-1", ..., "string-n", ""] or ["", "string-1", ..., "string-n", "+"]
                    merge = name.pop && (name.pop() === "+");

                    if (value && this.end()) {
                        return new (tree.Rule)(name, value, important, merge, memo, env.currentFileInfo);
                    } else {
                        furthest = i;
                        restore();
                        if (value && !tryAnonymous) {
                            return this.rule(true);
                        }
                    }
                }
            },
            anonymousValue: function () {
                var match;
                match = /^([^@+\/'"*`(;{}-]*);/.exec(current);
                if (match) {
                    i += match[0].length - 1;
                    return new(tree.Anonymous)(match[1]);
                }
            },

            //
            // An @import directive
            //
            //     @import "lib";
            //
            // Depending on our environemnt, importing is done differently:
            // In the browser, it's an XHR request, in Node, it would be a
            // file-system operation. The function used for importing is
            // stored in `import`, which we pass to the Import constructor.
            //
            "import": function () {
                var path, features, index = i;

                save();

                var dir = $re(/^@import?\s+/);

                var options = (dir ? this.importOptions() : null) || {};

                if (dir && (path = this.entities.quoted() || this.entities.url())) {
                    features = this.mediaFeatures();
                    if ($char(';')) {
                        features = features && new(tree.Value)(features);
                        return new(tree.Import)(path, features, options, index, env.currentFileInfo);
                    }
                }

                restore();
            },

            importOptions: function() {
                var o, options = {}, optionName, value;

                // list of options, surrounded by parens
                if (! $char('(')) { return null; }
                do {
                    o = this.importOption();
                    if (o) {
                        optionName = o;
                        value = true;
                        switch(optionName) {
                            case "css":
                                optionName = "less";
                                value = false;
                            break;
                            case "once":
                                optionName = "multiple";
                                value = false;
                            break;
                        }
                        options[optionName] = value;
                        if (! $char(',')) { break; }
                    }
                } while (o);
                expectChar(')');
                return options;
            },

            importOption: function() {
                var opt = $re(/^(less|css|multiple|once|inline|reference)/);
                if (opt) {
                    return opt[1];
                }
            },

            mediaFeature: function () {
                var entities = this.entities, nodes = [], e, p;
                do {
                    e = entities.keyword() || entities.variable();
                    if (e) {
                        nodes.push(e);
                    } else if ($char('(')) {
                        p = this.property();
                        e = this.value();
                        if ($char(')')) {
                            if (p && e) {
                                nodes.push(new(tree.Paren)(new(tree.Rule)(p, e, null, null, i, env.currentFileInfo, true)));
                            } else if (e) {
                                nodes.push(new(tree.Paren)(e));
                            } else {
                                return null;
                            }
                        } else { return null; }
                    }
                } while (e);

                if (nodes.length > 0) {
                    return new(tree.Expression)(nodes);
                }
            },

            mediaFeatures: function () {
                var entities = this.entities, features = [], e;
                do {
                    e = this.mediaFeature();
                    if (e) {
                        features.push(e);
                        if (! $char(',')) { break; }
                    } else {
                        e = entities.variable();
                        if (e) {
                            features.push(e);
                            if (! $char(',')) { break; }
                        }
                    }
                } while (e);

                return features.length > 0 ? features : null;
            },

            media: function () {
                var features, rules, media, debugInfo;

                if (env.dumpLineNumbers) {
                    debugInfo = getDebugInfo(i, input, env);
                }

                if ($re(/^@media/)) {
                    features = this.mediaFeatures();

                    rules = this.block();
                    if (rules) {
                        media = new(tree.Media)(rules, features, i, env.currentFileInfo);
                        if (env.dumpLineNumbers) {
                            media.debugInfo = debugInfo;
                        }
                        return media;
                    }
                }
            },

            //
            // A CSS Directive
            //
            //     @charset "utf-8";
            //
            directive: function () {
                var index = i, name, value, rules, nonVendorSpecificName,
                    hasBlock, hasIdentifier, hasExpression, identifier;

                if (input.charAt(i) !== '@') { return; }

                value = this['import']() || this.media();
                if (value) {
                    return value;
                }

                save();

                name = $re(/^@[a-z-]+/);
                
                if (!name) { return; }

                nonVendorSpecificName = name;
                if (name.charAt(1) == '-' && name.indexOf('-', 2) > 0) {
                    nonVendorSpecificName = "@" + name.slice(name.indexOf('-', 2) + 1);
                }

                switch(nonVendorSpecificName) {
                    case "@font-face":
                        hasBlock = true;
                        break;
                    case "@viewport":
                    case "@top-left":
                    case "@top-left-corner":
                    case "@top-center":
                    case "@top-right":
                    case "@top-right-corner":
                    case "@bottom-left":
                    case "@bottom-left-corner":
                    case "@bottom-center":
                    case "@bottom-right":
                    case "@bottom-right-corner":
                    case "@left-top":
                    case "@left-middle":
                    case "@left-bottom":
                    case "@right-top":
                    case "@right-middle":
                    case "@right-bottom":
                        hasBlock = true;
                        break;
                    case "@host":
                    case "@page":
                    case "@document":
                    case "@supports":
                    case "@keyframes":
                        hasBlock = true;
                        hasIdentifier = true;
                        break;
                    case "@namespace":
                        hasExpression = true;
                        break;
                }

                if (hasIdentifier) {
                    identifier = ($re(/^[^{]+/) || '').trim();
                    if (identifier) {
                        name += " " + identifier;
                    }
                }

                if (hasBlock) {
                    rules = this.block();
                    if (rules) {
                        return new(tree.Directive)(name, rules, index, env.currentFileInfo);
                    }
                } else {
                    value = hasExpression ? this.expression() : this.entity();
                    if (value && $char(';')) {
                        var directive = new(tree.Directive)(name, value, index, env.currentFileInfo);
                        if (env.dumpLineNumbers) {
                            directive.debugInfo = getDebugInfo(i, input, env);
                        }
                        return directive;
                    }
                }

                restore();
            },

            //
            // A Value is a comma-delimited list of Expressions
            //
            //     font-family: Baskerville, Georgia, serif;
            //
            // In a Rule, a Value represents everything after the `:`,
            // and before the `;`.
            //
            value: function () {
                var e, expressions = [];

                do {
                    e = this.expression();
                    if (e) {
                        expressions.push(e);
                        if (! $char(',')) { break; }
                    }
                } while(e);

                if (expressions.length > 0) {
                    return new(tree.Value)(expressions);
                }
            },
            important: function () {
                if (input.charAt(i) === '!') {
                    return $re(/^! *important/);
                }
            },
            sub: function () {
                var a, e;

                if ($char('(')) {
                    a = this.addition();
                    if (a) {
                        e = new(tree.Expression)([a]);
                        expectChar(')');
                        e.parens = true;
                        return e;
                    }
                }
            },
            multiplication: function () {
                var m, a, op, operation, isSpaced;
                m = this.operand();
                if (m) {
                    isSpaced = isWhitespace(input, i - 1);
                    while (true) {
                        if (peek(/^\/[*\/]/)) {
                            break;
                        }
                        op = $char('/') || $char('*');

                        if (!op) { break; }

                        a = this.operand();

                        if (!a) { break; }

                        m.parensInOp = true;
                        a.parensInOp = true;
                        operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                        isSpaced = isWhitespace(input, i - 1);
                    }
                    return operation || m;
                }
            },
            addition: function () {
                var m, a, op, operation, isSpaced;
                m = this.multiplication();
                if (m) {
                    isSpaced = isWhitespace(input, i - 1);
                    while (true) {
                        op = $re(/^[-+]\s+/) || (!isSpaced && ($char('+') || $char('-')));
                        if (!op) {
                            break;
                        }
                        a = this.multiplication();
                        if (!a) {
                            break;
                        }
                        
                        m.parensInOp = true;
                        a.parensInOp = true;
                        operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                        isSpaced = isWhitespace(input, i - 1);
                    }
                    return operation || m;
                }
            },
            conditions: function () {
                var a, b, index = i, condition;

                a = this.condition();
                if (a) {
                    while (true) {
                        if (!peek(/^,\s*(not\s*)?\(/) || !$char(',')) {
                            break;
                        }
                        b = this.condition();
                        if (!b) {
                            break;
                        }
                        condition = new(tree.Condition)('or', condition || a, b, index);
                    }
                    return condition || a;
                }
            },
            condition: function () {
                var entities = this.entities, index = i, negate = false,
                    a, b, c, op;

                if ($re(/^not/)) { negate = true; }
                expectChar('(');
                a = this.addition() || entities.keyword() || entities.quoted();
                if (a) {
                    op = $re(/^(?:>=|<=|=<|[<=>])/);
                    if (op) {
                        b = this.addition() || entities.keyword() || entities.quoted();
                        if (b) {
                            c = new(tree.Condition)(op, a, b, index, negate);
                        } else {
                            error('expected expression');
                        }
                    } else {
                        c = new(tree.Condition)('=', a, new(tree.Keyword)('true'), index, negate);
                    }
                    expectChar(')');
                    return $re(/^and/) ? new(tree.Condition)('and', c, this.condition()) : c;
                }
            },

            //
            // An operand is anything that can be part of an operation,
            // such as a Color, or a Variable
            //
            operand: function () {
                var entities = this.entities,
                    p = input.charAt(i + 1), negate;

                if (input.charAt(i) === '-' && (p === '@' || p === '(')) { negate = $char('-'); }
                var o = this.sub() || entities.dimension() ||
                        entities.color() || entities.variable() ||
                        entities.call();

                if (negate) {
                    o.parensInOp = true;
                    o = new(tree.Negative)(o);
                }

                return o;
            },

            //
            // Expressions either represent mathematical operations,
            // or white-space delimited Entities.
            //
            //     1px solid black
            //     @var * 2
            //
            expression: function () {
                var entities = [], e, delim;

                do {
                    e = this.addition() || this.entity();
                    if (e) {
                        entities.push(e);
                        // operations do not allow keyword "/" dimension (e.g. small/20px) so we support that here
                        if (!peek(/^\/[\/*]/)) {
                            delim = $char('/');
                            if (delim) {
                                entities.push(new(tree.Anonymous)(delim));
                            }
                        }
                    }
                } while (e);
                if (entities.length > 0) {
                    return new(tree.Expression)(entities);
                }
            },
            property: function () {
                var name = $re(/^(\*?-?[_a-zA-Z0-9-]+)\s*:/);
                if (name) {
                    return name[1];
                }
            },
            ruleProperty: function () {
                var c = current, name = [], index = [], length = 0;
                
                function match(re) {
                    var a = re.exec(c);
                    if (a) {
                        index.push(i + length);
                        length += a[0].length;
                        c = c.slice(a[1].length);
                        return name.push(a[1]);
                    }
                }

                match(/^(\*?)/);
                while (match(/^((?:[\w-]+)|(?:@\{[\w-]+\}))/)); // !
                if ((name.length > 1) && match(/^\s*(\+?)\s*:/)) {
                    // at last, we have the complete match now. move forward, 
                    // convert @{var}s to tree.Variable(s) and return:
                    skipWhitespace(length);
                    for (var k in name) {
                        if (name[k].charAt(0) === '@') {
                            name[k] = new tree.Variable('@' + name[k].slice(2, -1), 
                                index[k], env.currentFileInfo);
                        }
                    }
                    return name;
                }
            }
        }
    };
    return parser;
};
less.Parser.serializeVars = function(vars) {
    var s = '';

    for (var name in vars) {
        if (Object.hasOwnProperty.call(vars, name)) {
            var value = vars[name];
            s += ((name[0] === '@') ? '' : '@') + name +': '+ value +
                    ((('' + value).slice(-1) === ';') ? '' : ';');
        }
    }

    return s;
};
(function (tree) {

tree.functions = {
    rgb: function (r, g, b) {
        return this.rgba(r, g, b, 1.0);
    },
    rgba: function (r, g, b, a) {
        var rgb = [r, g, b].map(function (c) { return scaled(c, 255); });
        a = number(a);
        return new(tree.Color)(rgb, a);
    },
    hsl: function (h, s, l) {
        return this.hsla(h, s, l, 1.0);
    },
    hsla: function (h, s, l, a) {
        function hue(h) {
            h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
            if      (h * 6 < 1) { return m1 + (m2 - m1) * h * 6; }
            else if (h * 2 < 1) { return m2; }
            else if (h * 3 < 2) { return m1 + (m2 - m1) * (2/3 - h) * 6; }
            else                { return m1; }
        }

        h = (number(h) % 360) / 360;
        s = clamp(number(s)); l = clamp(number(l)); a = clamp(number(a));

        var m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s;
        var m1 = l * 2 - m2;

        return this.rgba(hue(h + 1/3) * 255,
                         hue(h)       * 255,
                         hue(h - 1/3) * 255,
                         a);
    },

    hsv: function(h, s, v) {
        return this.hsva(h, s, v, 1.0);
    },

    hsva: function(h, s, v, a) {
        h = ((number(h) % 360) / 360) * 360;
        s = number(s); v = number(v); a = number(a);

        var i, f;
        i = Math.floor((h / 60) % 6);
        f = (h / 60) - i;

        var vs = [v,
                  v * (1 - s),
                  v * (1 - f * s),
                  v * (1 - (1 - f) * s)];
        var perm = [[0, 3, 1],
                    [2, 0, 1],
                    [1, 0, 3],
                    [1, 2, 0],
                    [3, 1, 0],
                    [0, 1, 2]];

        return this.rgba(vs[perm[i][0]] * 255,
                         vs[perm[i][1]] * 255,
                         vs[perm[i][2]] * 255,
                         a);
    },

    hue: function (color) {
        return new(tree.Dimension)(Math.round(color.toHSL().h));
    },
    saturation: function (color) {
        return new(tree.Dimension)(Math.round(color.toHSL().s * 100), '%');
    },
    lightness: function (color) {
        return new(tree.Dimension)(Math.round(color.toHSL().l * 100), '%');
    },
    hsvhue: function(color) {
        return new(tree.Dimension)(Math.round(color.toHSV().h));
    },
    hsvsaturation: function (color) {
        return new(tree.Dimension)(Math.round(color.toHSV().s * 100), '%');
    },
    hsvvalue: function (color) {
        return new(tree.Dimension)(Math.round(color.toHSV().v * 100), '%');
    },
    red: function (color) {
        return new(tree.Dimension)(color.rgb[0]);
    },
    green: function (color) {
        return new(tree.Dimension)(color.rgb[1]);
    },
    blue: function (color) {
        return new(tree.Dimension)(color.rgb[2]);
    },
    alpha: function (color) {
        return new(tree.Dimension)(color.toHSL().a);
    },
    luma: function (color) {
        return new(tree.Dimension)(Math.round(color.luma() * color.alpha * 100), '%');
    },
    saturate: function (color, amount) {
        // filter: saturate(3.2);
        // should be kept as is, so check for color
        if (!color.rgb) {
            return null;
        }
        var hsl = color.toHSL();

        hsl.s += amount.value / 100;
        hsl.s = clamp(hsl.s);
        return hsla(hsl);
    },
    desaturate: function (color, amount) {
        var hsl = color.toHSL();

        hsl.s -= amount.value / 100;
        hsl.s = clamp(hsl.s);
        return hsla(hsl);
    },
    lighten: function (color, amount) {
        var hsl = color.toHSL();

        hsl.l += amount.value / 100;
        hsl.l = clamp(hsl.l);
        return hsla(hsl);
    },
    darken: function (color, amount) {
        var hsl = color.toHSL();

        hsl.l -= amount.value / 100;
        hsl.l = clamp(hsl.l);
        return hsla(hsl);
    },
    fadein: function (color, amount) {
        var hsl = color.toHSL();

        hsl.a += amount.value / 100;
        hsl.a = clamp(hsl.a);
        return hsla(hsl);
    },
    fadeout: function (color, amount) {
        var hsl = color.toHSL();

        hsl.a -= amount.value / 100;
        hsl.a = clamp(hsl.a);
        return hsla(hsl);
    },
    fade: function (color, amount) {
        var hsl = color.toHSL();

        hsl.a = amount.value / 100;
        hsl.a = clamp(hsl.a);
        return hsla(hsl);
    },
    spin: function (color, amount) {
        var hsl = color.toHSL();
        var hue = (hsl.h + amount.value) % 360;

        hsl.h = hue < 0 ? 360 + hue : hue;

        return hsla(hsl);
    },
    //
    // Copyright (c) 2006-2009 Hampton Catlin, Nathan Weizenbaum, and Chris Eppstein
    // http://sass-lang.com
    //
    mix: function (color1, color2, weight) {
        if (!weight) {
            weight = new(tree.Dimension)(50);
        }
        var p = weight.value / 100.0;
        var w = p * 2 - 1;
        var a = color1.toHSL().a - color2.toHSL().a;

        var w1 = (((w * a == -1) ? w : (w + a) / (1 + w * a)) + 1) / 2.0;
        var w2 = 1 - w1;

        var rgb = [color1.rgb[0] * w1 + color2.rgb[0] * w2,
                   color1.rgb[1] * w1 + color2.rgb[1] * w2,
                   color1.rgb[2] * w1 + color2.rgb[2] * w2];

        var alpha = color1.alpha * p + color2.alpha * (1 - p);

        return new(tree.Color)(rgb, alpha);
    },
    greyscale: function (color) {
        return this.desaturate(color, new(tree.Dimension)(100));
    },
    contrast: function (color, dark, light, threshold) {
        // filter: contrast(3.2);
        // should be kept as is, so check for color
        if (!color.rgb) {
            return null;
        }
        if (typeof light === 'undefined') {
            light = this.rgba(255, 255, 255, 1.0);
        }
        if (typeof dark === 'undefined') {
            dark = this.rgba(0, 0, 0, 1.0);
        }
        //Figure out which is actually light and dark!
        if (dark.luma() > light.luma()) {
            var t = light;
            light = dark;
            dark = t;
        }
        if (typeof threshold === 'undefined') {
            threshold = 0.43;
        } else {
            threshold = number(threshold);
        }
        if (color.luma() < threshold) {
            return light;
        } else {
            return dark;
        }
    },
    e: function (str) {
        return new(tree.Anonymous)(str instanceof tree.JavaScript ? str.evaluated : str);
    },
    escape: function (str) {
        return new(tree.Anonymous)(encodeURI(str.value).replace(/=/g, "%3D").replace(/:/g, "%3A").replace(/#/g, "%23").replace(/;/g, "%3B").replace(/\(/g, "%28").replace(/\)/g, "%29"));
    },
    '%': function (quoted /* arg, arg, ...*/) {
        var args = Array.prototype.slice.call(arguments, 1),
            str = quoted.value;

        for (var i = 0; i < args.length; i++) {
            /*jshint loopfunc:true */
            str = str.replace(/%[sda]/i, function(token) {
                var value = token.match(/s/i) ? args[i].value : args[i].toCSS();
                return token.match(/[A-Z]$/) ? encodeURIComponent(value) : value;
            });
        }
        str = str.replace(/%%/g, '%');
        return new(tree.Quoted)('"' + str + '"', str);
    },
    unit: function (val, unit) {
        if(!(val instanceof tree.Dimension)) {
            throw { type: "Argument", message: "the first argument to unit must be a number" + (val instanceof tree.Operation ? ". Have you forgotten parenthesis?" : "") };
        }
        return new(tree.Dimension)(val.value, unit ? unit.toCSS() : "");
    },
    convert: function (val, unit) {
        return val.convertTo(unit.value);
    },
    round: function (n, f) {
        var fraction = typeof(f) === "undefined" ? 0 : f.value;
        return _math(function(num) { return num.toFixed(fraction); }, null, n);
    },
    pi: function () {
        return new(tree.Dimension)(Math.PI);
    },
    mod: function(a, b) {
        return new(tree.Dimension)(a.value % b.value, a.unit);
    },
    pow: function(x, y) {
        if (typeof x === "number" && typeof y === "number") {
            x = new(tree.Dimension)(x);
            y = new(tree.Dimension)(y);
        } else if (!(x instanceof tree.Dimension) || !(y instanceof tree.Dimension)) {
            throw { type: "Argument", message: "arguments must be numbers" };
        }

        return new(tree.Dimension)(Math.pow(x.value, y.value), x.unit);
    },
    _minmax: function (isMin, args) {
        args = Array.prototype.slice.call(args);
        switch(args.length) {
        case 0: throw { type: "Argument", message: "one or more arguments required" };
        case 1: return args[0];
        }
        var i, j, current, currentUnified, referenceUnified, unit,
            order  = [], // elems only contains original argument values.
            values = {}; // key is the unit.toString() for unified tree.Dimension values,
                         // value is the index into the order array.
        for (i = 0; i < args.length; i++) {
            current = args[i];
            if (!(current instanceof tree.Dimension)) {
                order.push(current);
                continue;
            }
            currentUnified = current.unify();
            unit = currentUnified.unit.toString();
            j = values[unit];
            if (j === undefined) {
                values[unit] = order.length;
                order.push(current);
                continue;
            }
            referenceUnified = order[j].unify();
            if ( isMin && currentUnified.value < referenceUnified.value ||
                !isMin && currentUnified.value > referenceUnified.value) {
                order[j] = current;
            }
        }
        if (order.length == 1) {
            return order[0];
        }
        args = order.map(function (a) { return a.toCSS(this.env); })
                    .join(this.env.compress ? "," : ", ");
        return new(tree.Anonymous)((isMin ? "min" : "max") + "(" + args + ")");
    },
    min: function () {
        return this._minmax(true, arguments);
    },
    max: function () {
        return this._minmax(false, arguments);
    },
    argb: function (color) {
        return new(tree.Anonymous)(color.toARGB());
    },
    percentage: function (n) {
        return new(tree.Dimension)(n.value * 100, '%');
    },
    color: function (n) {
        if (n instanceof tree.Quoted) {
            var colorCandidate = n.value,
                returnColor;
            returnColor = tree.Color.fromKeyword(colorCandidate);
            if (returnColor) {
                return returnColor;
            }
            if (/^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})/.test(colorCandidate)) {
                return new(tree.Color)(colorCandidate.slice(1));
            }
            throw { type: "Argument", message: "argument must be a color keyword or 3/6 digit hex e.g. #FFF" };
        } else {
            throw { type: "Argument", message: "argument must be a string" };
        }
    },
    iscolor: function (n) {
        return this._isa(n, tree.Color);
    },
    isnumber: function (n) {
        return this._isa(n, tree.Dimension);
    },
    isstring: function (n) {
        return this._isa(n, tree.Quoted);
    },
    iskeyword: function (n) {
        return this._isa(n, tree.Keyword);
    },
    isurl: function (n) {
        return this._isa(n, tree.URL);
    },
    ispixel: function (n) {
        return this.isunit(n, 'px');
    },
    ispercentage: function (n) {
        return this.isunit(n, '%');
    },
    isem: function (n) {
        return this.isunit(n, 'em');
    },
    isunit: function (n, unit) {
        return (n instanceof tree.Dimension) && n.unit.is(unit.value || unit) ? tree.True : tree.False;
    },
    _isa: function (n, Type) {
        return (n instanceof Type) ? tree.True : tree.False;
    },
    tint: function(color, amount) {
        return this.mix(this.rgb(255,255,255), color, amount);
    },
    shade: function(color, amount) {
        return this.mix(this.rgb(0, 0, 0), color, amount);
    },   
    extract: function(values, index) {
        index = index.value - 1; // (1-based index)       
        // handle non-array values as an array of length 1
        // return 'undefined' if index is invalid
        return Array.isArray(values.value) 
            ? values.value[index] : Array(values)[index];
    },
    length: function(values) {
        var n = Array.isArray(values.value) ? values.value.length : 1;
        return new tree.Dimension(n);
    },

    "data-uri": function(mimetypeNode, filePathNode) {

        if (typeof window !== 'undefined') {
            return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
        }

        var mimetype = mimetypeNode.value;
        var filePath = (filePathNode && filePathNode.value);

        var fs = require("fs"),
            path = require("path"),
            useBase64 = false;

        if (arguments.length < 2) {
            filePath = mimetype;
        }

        if (this.env.isPathRelative(filePath)) {
            if (this.currentFileInfo.relativeUrls) {
                filePath = path.join(this.currentFileInfo.currentDirectory, filePath);
            } else {
                filePath = path.join(this.currentFileInfo.entryPath, filePath);
            }
        }

        // detect the mimetype if not given
        if (arguments.length < 2) {
            var mime;
            try {
                mime = require('mime');
            } catch (ex) {
                mime = tree._mime;
            }

            mimetype = mime.lookup(filePath);

            // use base 64 unless it's an ASCII or UTF-8 format
            var charset = mime.charsets.lookup(mimetype);
            useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
            if (useBase64) { mimetype += ';base64'; }
        }
        else {
            useBase64 = /;base64$/.test(mimetype);
        }

        var buf = fs.readFileSync(filePath);

        // IE8 cannot handle a data-uri larger than 32KB. If this is exceeded
        // and the --ieCompat flag is enabled, return a normal url() instead.
        var DATA_URI_MAX_KB = 32,
            fileSizeInKB = parseInt((buf.length / 1024), 10);
        if (fileSizeInKB >= DATA_URI_MAX_KB) {

            if (this.env.ieCompat !== false) {
                if (!this.env.silent) {
                    console.warn("Skipped data-uri embedding of %s because its size (%dKB) exceeds IE8-safe %dKB!", filePath, fileSizeInKB, DATA_URI_MAX_KB);
                }

                return new tree.URL(filePathNode || mimetypeNode, this.currentFileInfo).eval(this.env);
            }
        }

        buf = useBase64 ? buf.toString('base64')
                        : encodeURIComponent(buf);

        var uri = "\"data:" + mimetype + ',' + buf + "\"";
        return new(tree.URL)(new(tree.Anonymous)(uri));
    },

    "svg-gradient": function(direction) {

        function throwArgumentDescriptor() {
            throw { type: "Argument", message: "svg-gradient expects direction, start_color [start_position], [color position,]..., end_color [end_position]" };
        }

        if (arguments.length < 3) {
            throwArgumentDescriptor();
        }
        var stops = Array.prototype.slice.call(arguments, 1),
            gradientDirectionSvg,
            gradientType = "linear",
            rectangleDimension = 'x="0" y="0" width="1" height="1"',
            useBase64 = true,
            renderEnv = {compress: false},
            returner,
            directionValue = direction.toCSS(renderEnv),
            i, color, position, positionValue, alpha;

        switch (directionValue) {
            case "to bottom":
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="0%" y2="100%"';
                break;
            case "to right":
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="0%"';
                break;
            case "to bottom right":
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="100%"';
                break;
            case "to top right":
                gradientDirectionSvg = 'x1="0%" y1="100%" x2="100%" y2="0%"';
                break;
            case "ellipse":
            case "ellipse at center":
                gradientType = "radial";
                gradientDirectionSvg = 'cx="50%" cy="50%" r="75%"';
                rectangleDimension = 'x="-50" y="-50" width="101" height="101"';
                break;
            default:
                throw { type: "Argument", message: "svg-gradient direction must be 'to bottom', 'to right', 'to bottom right', 'to top right' or 'ellipse at center'" };
        }
        returner = '<?xml version="1.0" ?>' +
            '<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="100%" height="100%" viewBox="0 0 1 1" preserveAspectRatio="none">' +
            '<' + gradientType + 'Gradient id="gradient" gradientUnits="userSpaceOnUse" ' + gradientDirectionSvg + '>';

        for (i = 0; i < stops.length; i+= 1) {
            if (stops[i].value) {
                color = stops[i].value[0];
                position = stops[i].value[1];
            } else {
                color = stops[i];
                position = undefined;
            }

            if (!(color instanceof tree.Color) || (!((i === 0 || i+1 === stops.length) && position === undefined) && !(position instanceof tree.Dimension))) {
                throwArgumentDescriptor();
            }
            positionValue = position ? position.toCSS(renderEnv) : i === 0 ? "0%" : "100%";
            alpha = color.alpha;
            returner += '<stop offset="' + positionValue + '" stop-color="' + color.toRGB() + '"' + (alpha < 1 ? ' stop-opacity="' + alpha + '"' : '') + '/>';
        }
        returner += '</' + gradientType + 'Gradient>' +
                    '<rect ' + rectangleDimension + ' fill="url(#gradient)" /></svg>';

        if (useBase64) {
            // only works in node, needs interface to what is supported in environment
            try {
                returner = new Buffer(returner).toString('base64');
            } catch(e) {
                useBase64 = false;
            }
        }

        returner = "'data:image/svg+xml" + (useBase64 ? ";base64" : "") + "," + returner + "'";
        return new(tree.URL)(new(tree.Anonymous)(returner));
    }
};

// these static methods are used as a fallback when the optional 'mime' dependency is missing
tree._mime = {
    // this map is intentionally incomplete
    // if you want more, install 'mime' dep
    _types: {
        '.htm' : 'text/html',
        '.html': 'text/html',
        '.gif' : 'image/gif',
        '.jpg' : 'image/jpeg',
        '.jpeg': 'image/jpeg',
        '.png' : 'image/png'
    },
    lookup: function (filepath) {
        var ext = require('path').extname(filepath),
            type = tree._mime._types[ext];
        if (type === undefined) {
            throw new Error('Optional dependency "mime" is required for ' + ext);
        }
        return type;
    },
    charsets: {
        lookup: function (type) {
            // assumes all text types are UTF-8
            return type && (/^text\//).test(type) ? 'UTF-8' : '';
        }
    }
};

// Math

var mathFunctions = {
 // name,  unit
    ceil:  null, 
    floor: null, 
    sqrt:  null, 
    abs:   null,
    tan:   "", 
    sin:   "", 
    cos:   "",
    atan:  "rad", 
    asin:  "rad", 
    acos:  "rad"
};

function _math(fn, unit, n) {
    if (!(n instanceof tree.Dimension)) {
        throw { type: "Argument", message: "argument must be a number" };
    }
    if (unit == null) {
        unit = n.unit;
    } else {
        n = n.unify();
    }
    return new(tree.Dimension)(fn(parseFloat(n.value)), unit);
}

// ~ End of Math

// Color Blending
// ref: http://www.w3.org/TR/compositing-1

function colorBlend(mode, color1, color2) {
    var ab = color1.alpha, cb, // backdrop
        as = color2.alpha, cs, // source
        ar, cr, r = [];        // result
        
    ar = as + ab * (1 - as);
    for (var i = 0; i < 3; i++) {
        cb = color1.rgb[i] / 255;
        cs = color2.rgb[i] / 255;
        cr = mode(cb, cs);
        if (ar) {
            cr = (as * cs + ab * (cb 
                - as * (cb + cs - cr))) / ar;
        }
        r[i] = cr * 255;
    }
    
    return new(tree.Color)(r, ar);
}

var colorBlendMode = {
    multiply: function(cb, cs) {
        return cb * cs;
    },
    screen: function(cb, cs) {
        return cb + cs - cb * cs;
    },   
    overlay: function(cb, cs) {
        cb *= 2;
        return (cb <= 1)
            ? colorBlendMode.multiply(cb, cs)
            : colorBlendMode.screen(cb - 1, cs);
    },
    softlight: function(cb, cs) {
        var d = 1, e = cb;
        if (cs > 0.5) {
            e = 1;
            d = (cb > 0.25) ? Math.sqrt(cb)
                : ((16 * cb - 12) * cb + 4) * cb;
        }            
        return cb - (1 - 2 * cs) * e * (d - cb);
    },
    hardlight: function(cb, cs) {
        return colorBlendMode.overlay(cs, cb);
    },
    difference: function(cb, cs) {
        return Math.abs(cb - cs);
    },
    exclusion: function(cb, cs) {
        return cb + cs - 2 * cb * cs;
    },

    // non-w3c functions:
    average: function(cb, cs) {
        return (cb + cs) / 2;
    },
    negation: function(cb, cs) {
        return 1 - Math.abs(cb + cs - 1);
    }
};

// ~ End of Color Blending

tree.defaultFunc = {
    eval: function () {
        var v = this.value_, e = this.error_;
        if (e) {
            throw e;
        }
        if (v != null) {
            return v ? tree.True : tree.False;
        }
    },
    value: function (v) {
        this.value_ = v;
    },
    error: function (e) {
        this.error_ = e;
    },
    reset: function () {
        this.value_ = this.error_ = null;
    }
};

function initFunctions() {
    var f, tf = tree.functions;
    
    // math
    for (f in mathFunctions) {
        if (mathFunctions.hasOwnProperty(f)) {
            tf[f] = _math.bind(null, Math[f], mathFunctions[f]);
        }
    }
    
    // color blending
    for (f in colorBlendMode) {
        if (colorBlendMode.hasOwnProperty(f)) {
            tf[f] = colorBlend.bind(null, colorBlendMode[f]);
        }
    }
    
    // default
    f = tree.defaultFunc;
    tf["default"] = f.eval.bind(f);
    
} initFunctions();

function hsla(color) {
    return tree.functions.hsla(color.h, color.s, color.l, color.a);
}

function scaled(n, size) {
    if (n instanceof tree.Dimension && n.unit.is('%')) {
        return parseFloat(n.value * size / 100);
    } else {
        return number(n);
    }
}

function number(n) {
    if (n instanceof tree.Dimension) {
        return parseFloat(n.unit.is('%') ? n.value / 100 : n.value);
    } else if (typeof(n) === 'number') {
        return n;
    } else {
        throw {
            error: "RuntimeError",
            message: "color functions take numbers as parameters"
        };
    }
}

function clamp(val) {
    return Math.min(1, Math.max(0, val));
}

tree.functionCall = function(env, currentFileInfo) {
    this.env = env;
    this.currentFileInfo = currentFileInfo;
};

tree.functionCall.prototype = tree.functions;

})(require('./tree'));

(function (tree) {
    tree.colors = {
        'aliceblue':'#f0f8ff',
        'antiquewhite':'#faebd7',
        'aqua':'#00ffff',
        'aquamarine':'#7fffd4',
        'azure':'#f0ffff',
        'beige':'#f5f5dc',
        'bisque':'#ffe4c4',
        'black':'#000000',
        'blanchedalmond':'#ffebcd',
        'blue':'#0000ff',
        'blueviolet':'#8a2be2',
        'brown':'#a52a2a',
        'burlywood':'#deb887',
        'cadetblue':'#5f9ea0',
        'chartreuse':'#7fff00',
        'chocolate':'#d2691e',
        'coral':'#ff7f50',
        'cornflowerblue':'#6495ed',
        'cornsilk':'#fff8dc',
        'crimson':'#dc143c',
        'cyan':'#00ffff',
        'darkblue':'#00008b',
        'darkcyan':'#008b8b',
        'darkgoldenrod':'#b8860b',
        'darkgray':'#a9a9a9',
        'darkgrey':'#a9a9a9',
        'darkgreen':'#006400',
        'darkkhaki':'#bdb76b',
        'darkmagenta':'#8b008b',
        'darkolivegreen':'#556b2f',
        'darkorange':'#ff8c00',
        'darkorchid':'#9932cc',
        'darkred':'#8b0000',
        'darksalmon':'#e9967a',
        'darkseagreen':'#8fbc8f',
        'darkslateblue':'#483d8b',
        'darkslategray':'#2f4f4f',
        'darkslategrey':'#2f4f4f',
        'darkturquoise':'#00ced1',
        'darkviolet':'#9400d3',
        'deeppink':'#ff1493',
        'deepskyblue':'#00bfff',
        'dimgray':'#696969',
        'dimgrey':'#696969',
        'dodgerblue':'#1e90ff',
        'firebrick':'#b22222',
        'floralwhite':'#fffaf0',
        'forestgreen':'#228b22',
        'fuchsia':'#ff00ff',
        'gainsboro':'#dcdcdc',
        'ghostwhite':'#f8f8ff',
        'gold':'#ffd700',
        'goldenrod':'#daa520',
        'gray':'#808080',
        'grey':'#808080',
        'green':'#008000',
        'greenyellow':'#adff2f',
        'honeydew':'#f0fff0',
        'hotpink':'#ff69b4',
        'indianred':'#cd5c5c',
        'indigo':'#4b0082',
        'ivory':'#fffff0',
        'khaki':'#f0e68c',
        'lavender':'#e6e6fa',
        'lavenderblush':'#fff0f5',
        'lawngreen':'#7cfc00',
        'lemonchiffon':'#fffacd',
        'lightblue':'#add8e6',
        'lightcoral':'#f08080',
        'lightcyan':'#e0ffff',
        'lightgoldenrodyellow':'#fafad2',
        'lightgray':'#d3d3d3',
        'lightgrey':'#d3d3d3',
        'lightgreen':'#90ee90',
        'lightpink':'#ffb6c1',
        'lightsalmon':'#ffa07a',
        'lightseagreen':'#20b2aa',
        'lightskyblue':'#87cefa',
        'lightslategray':'#778899',
        'lightslategrey':'#778899',
        'lightsteelblue':'#b0c4de',
        'lightyellow':'#ffffe0',
        'lime':'#00ff00',
        'limegreen':'#32cd32',
        'linen':'#faf0e6',
        'magenta':'#ff00ff',
        'maroon':'#800000',
        'mediumaquamarine':'#66cdaa',
        'mediumblue':'#0000cd',
        'mediumorchid':'#ba55d3',
        'mediumpurple':'#9370d8',
        'mediumseagreen':'#3cb371',
        'mediumslateblue':'#7b68ee',
        'mediumspringgreen':'#00fa9a',
        'mediumturquoise':'#48d1cc',
        'mediumvioletred':'#c71585',
        'midnightblue':'#191970',
        'mintcream':'#f5fffa',
        'mistyrose':'#ffe4e1',
        'moccasin':'#ffe4b5',
        'navajowhite':'#ffdead',
        'navy':'#000080',
        'oldlace':'#fdf5e6',
        'olive':'#808000',
        'olivedrab':'#6b8e23',
        'orange':'#ffa500',
        'orangered':'#ff4500',
        'orchid':'#da70d6',
        'palegoldenrod':'#eee8aa',
        'palegreen':'#98fb98',
        'paleturquoise':'#afeeee',
        'palevioletred':'#d87093',
        'papayawhip':'#ffefd5',
        'peachpuff':'#ffdab9',
        'peru':'#cd853f',
        'pink':'#ffc0cb',
        'plum':'#dda0dd',
        'powderblue':'#b0e0e6',
        'purple':'#800080',
        'red':'#ff0000',
        'rosybrown':'#bc8f8f',
        'royalblue':'#4169e1',
        'saddlebrown':'#8b4513',
        'salmon':'#fa8072',
        'sandybrown':'#f4a460',
        'seagreen':'#2e8b57',
        'seashell':'#fff5ee',
        'sienna':'#a0522d',
        'silver':'#c0c0c0',
        'skyblue':'#87ceeb',
        'slateblue':'#6a5acd',
        'slategray':'#708090',
        'slategrey':'#708090',
        'snow':'#fffafa',
        'springgreen':'#00ff7f',
        'steelblue':'#4682b4',
        'tan':'#d2b48c',
        'teal':'#008080',
        'thistle':'#d8bfd8',
        'tomato':'#ff6347',
        'turquoise':'#40e0d0',
        'violet':'#ee82ee',
        'wheat':'#f5deb3',
        'white':'#ffffff',
        'whitesmoke':'#f5f5f5',
        'yellow':'#ffff00',
        'yellowgreen':'#9acd32'
    };
})(require('./tree'));

(function (tree) {

tree.debugInfo = function(env, ctx, lineSeperator) {
    var result="";
    if (env.dumpLineNumbers && !env.compress) {
        switch(env.dumpLineNumbers) {
            case 'comments':
                result = tree.debugInfo.asComment(ctx);
                break;
            case 'mediaquery':
                result = tree.debugInfo.asMediaQuery(ctx);
                break;
            case 'all':
                result = tree.debugInfo.asComment(ctx) + (lineSeperator || "") + tree.debugInfo.asMediaQuery(ctx);
                break;
        }
    }
    return result;
};

tree.debugInfo.asComment = function(ctx) {
    return '/* line ' + ctx.debugInfo.lineNumber + ', ' + ctx.debugInfo.fileName + ' */\n';
};

tree.debugInfo.asMediaQuery = function(ctx) {
    return '@media -sass-debug-info{filename{font-family:' +
        ('file://' + ctx.debugInfo.fileName).replace(/([.:/\\])/g, function (a) {
            if (a == '\\') {
                a = '\/';
            }
            return '\\' + a;
        }) +
        '}line{font-family:\\00003' + ctx.debugInfo.lineNumber + '}}\n';
};

tree.find = function (obj, fun) {
    for (var i = 0, r; i < obj.length; i++) {
        r = fun.call(obj, obj[i]);
        if (r) { return r; }
    }
    return null;
};

tree.jsify = function (obj) {
    if (Array.isArray(obj.value) && (obj.value.length > 1)) {
        return '[' + obj.value.map(function (v) { return v.toCSS(false); }).join(', ') + ']';
    } else {
        return obj.toCSS(false);
    }
};

tree.toCSS = function (env) {
    var strs = [];
    this.genCSS(env, {
        add: function(chunk, fileInfo, index) {
            strs.push(chunk);
        },
        isEmpty: function () {
            return strs.length === 0;
        }
    });
    return strs.join('');
};

tree.outputRuleset = function (env, output, rules) {
    var ruleCnt = rules.length, i;
    env.tabLevel = (env.tabLevel | 0) + 1;

    // Compressed
    if (env.compress) {
        output.add('{');
        for (i = 0; i < ruleCnt; i++) {
            rules[i].genCSS(env, output);
        }
        output.add('}');
        env.tabLevel--;
        return;
    }

    // Non-compressed
    var tabSetStr = '\n' + Array(env.tabLevel).join("  "), tabRuleStr = tabSetStr + "  ";
    if (!ruleCnt) {
        output.add(" {" + tabSetStr + '}');
    } else {
        output.add(" {" + tabRuleStr);
        rules[0].genCSS(env, output);
        for (i = 1; i < ruleCnt; i++) {
            output.add(tabRuleStr);
            rules[i].genCSS(env, output);
        }
        output.add(tabSetStr + '}');
    }

    env.tabLevel--;
};

})(require('./tree'));

(function (tree) {

tree.Alpha = function (val) {
    this.value = val;
};
tree.Alpha.prototype = {
    type: "Alpha",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    eval: function (env) {
        if (this.value.eval) { return new tree.Alpha(this.value.eval(env)); }
        return this;
    },
    genCSS: function (env, output) {
        output.add("alpha(opacity=");

        if (this.value.genCSS) {
            this.value.genCSS(env, output);
        } else {
            output.add(this.value);
        }

        output.add(")");
    },
    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {

tree.Anonymous = function (string, index, currentFileInfo, mapLines) {
    this.value = string.value || string;
    this.index = index;
    this.mapLines = mapLines;
    this.currentFileInfo = currentFileInfo;
};
tree.Anonymous.prototype = {
    type: "Anonymous",
    eval: function () { 
        return new tree.Anonymous(this.value, this.index, this.currentFileInfo, this.mapLines);
    },
    compare: function (x) {
        if (!x.toCSS) {
            return -1;
        }
        
        var left = this.toCSS(),
            right = x.toCSS();
        
        if (left === right) {
            return 0;
        }
        
        return left < right ? -1 : 1;
    },
    genCSS: function (env, output) {
        output.add(this.value, this.currentFileInfo, this.index, this.mapLines);
    },
    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {

tree.Assignment = function (key, val) {
    this.key = key;
    this.value = val;
};
tree.Assignment.prototype = {
    type: "Assignment",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    eval: function (env) {
        if (this.value.eval) {
            return new(tree.Assignment)(this.key, this.value.eval(env));
        }
        return this;
    },
    genCSS: function (env, output) {
        output.add(this.key + '=');
        if (this.value.genCSS) {
            this.value.genCSS(env, output);
        } else {
            output.add(this.value);
        }
    },
    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {

//
// A function call node.
//
tree.Call = function (name, args, index, currentFileInfo) {
    this.name = name;
    this.args = args;
    this.index = index;
    this.currentFileInfo = currentFileInfo;
};
tree.Call.prototype = {
    type: "Call",
    accept: function (visitor) {
        if (this.args) {
            this.args = visitor.visitArray(this.args);
        }
    },
    //
    // When evaluating a function call,
    // we either find the function in `tree.functions` [1],
    // in which case we call it, passing the  evaluated arguments,
    // if this returns null or we cannot find the function, we 
    // simply print it out as it appeared originally [2].
    //
    // The *functions.js* file contains the built-in functions.
    //
    // The reason why we evaluate the arguments, is in the case where
    // we try to pass a variable to a function, like: `saturate(@color)`.
    // The function should receive the value, not the variable.
    //
    eval: function (env) {
        var args = this.args.map(function (a) { return a.eval(env); }),
            nameLC = this.name.toLowerCase(),
            result, func;

        if (nameLC in tree.functions) { // 1.
            try {
                func = new tree.functionCall(env, this.currentFileInfo);
                result = func[nameLC].apply(func, args);
                if (result != null) {
                    return result;
                }
            } catch (e) {
                throw { type: e.type || "Runtime",
                        message: "error evaluating function `" + this.name + "`" +
                                 (e.message ? ': ' + e.message : ''),
                        index: this.index, filename: this.currentFileInfo.filename };
            }
        }

        return new tree.Call(this.name, args, this.index, this.currentFileInfo);
    },

    genCSS: function (env, output) {
        output.add(this.name + "(", this.currentFileInfo, this.index);

        for(var i = 0; i < this.args.length; i++) {
            this.args[i].genCSS(env, output);
            if (i + 1 < this.args.length) {
                output.add(", ");
            }
        }

        output.add(")");
    },

    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {
//
// RGB Colors - #ff0014, #eee
//
tree.Color = function (rgb, a) {
    //
    // The end goal here, is to parse the arguments
    // into an integer triplet, such as `128, 255, 0`
    //
    // This facilitates operations and conversions.
    //
    if (Array.isArray(rgb)) {
        this.rgb = rgb;
    } else if (rgb.length == 6) {
        this.rgb = rgb.match(/.{2}/g).map(function (c) {
            return parseInt(c, 16);
        });
    } else {
        this.rgb = rgb.split('').map(function (c) {
            return parseInt(c + c, 16);
        });
    }
    this.alpha = typeof(a) === 'number' ? a : 1;
};

var transparentKeyword = "transparent";

tree.Color.prototype = {
    type: "Color",
    eval: function () { return this; },
    luma: function () { return (0.2126 * this.rgb[0] / 255) + (0.7152 * this.rgb[1] / 255) + (0.0722 * this.rgb[2] / 255); },

    genCSS: function (env, output) {
        output.add(this.toCSS(env));
    },
    toCSS: function (env, doNotCompress) {
        var compress = env && env.compress && !doNotCompress;

        // If we have some transparency, the only way to represent it
        // is via `rgba`. Otherwise, we use the hex representation,
        // which has better compatibility with older browsers.
        // Values are capped between `0` and `255`, rounded and zero-padded.
        if (this.alpha < 1) {
            if (this.alpha === 0 && this.isTransparentKeyword) {
                return transparentKeyword;
            }
            return "rgba(" + this.rgb.map(function (c) {
                return clamp(Math.round(c), 255);
            }).concat(clamp(this.alpha, 1))
                .join(',' + (compress ? '' : ' ')) + ")";
        } else {
            var color = this.toRGB();

            if (compress) {
                var splitcolor = color.split('');

                // Convert color to short format
                if (splitcolor[1] === splitcolor[2] && splitcolor[3] === splitcolor[4] && splitcolor[5] === splitcolor[6]) {
                    color = '#' + splitcolor[1] + splitcolor[3] + splitcolor[5];
                }
            }

            return color;
        }
    },

    //
    // Operations have to be done per-channel, if not,
    // channels will spill onto each other. Once we have
    // our result, in the form of an integer triplet,
    // we create a new Color node to hold the result.
    //
    operate: function (env, op, other) {
        var rgb = [];
        var alpha = this.alpha * (1 - other.alpha) + other.alpha;
        for (var c = 0; c < 3; c++) {
            rgb[c] = tree.operate(env, op, this.rgb[c], other.rgb[c]);
        }
        return new(tree.Color)(rgb, alpha);
    },

    toRGB: function () {
        return toHex(this.rgb);
    },

    toHSL: function () {
        var r = this.rgb[0] / 255,
            g = this.rgb[1] / 255,
            b = this.rgb[2] / 255,
            a = this.alpha;

        var max = Math.max(r, g, b), min = Math.min(r, g, b);
        var h, s, l = (max + min) / 2, d = max - min;

        if (max === min) {
            h = s = 0;
        } else {
            s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

            switch (max) {
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2;               break;
                case b: h = (r - g) / d + 4;               break;
            }
            h /= 6;
        }
        return { h: h * 360, s: s, l: l, a: a };
    },
    //Adapted from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
    toHSV: function () {
        var r = this.rgb[0] / 255,
            g = this.rgb[1] / 255,
            b = this.rgb[2] / 255,
            a = this.alpha;

        var max = Math.max(r, g, b), min = Math.min(r, g, b);
        var h, s, v = max;

        var d = max - min;
        if (max === 0) {
            s = 0;
        } else {
            s = d / max;
        }

        if (max === min) {
            h = 0;
        } else {
            switch(max){
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2; break;
                case b: h = (r - g) / d + 4; break;
            }
            h /= 6;
        }
        return { h: h * 360, s: s, v: v, a: a };
    },
    toARGB: function () {
        return toHex([this.alpha * 255].concat(this.rgb));
    },
    compare: function (x) {
        if (!x.rgb) {
            return -1;
        }
        
        return (x.rgb[0] === this.rgb[0] &&
            x.rgb[1] === this.rgb[1] &&
            x.rgb[2] === this.rgb[2] &&
            x.alpha === this.alpha) ? 0 : -1;
    }
};

tree.Color.fromKeyword = function(keyword) {
    if (tree.colors.hasOwnProperty(keyword)) {
        // detect named color
        return new(tree.Color)(tree.colors[keyword].slice(1));
    }
    if (keyword === transparentKeyword) {
        var transparent = new(tree.Color)([0, 0, 0], 0);
        transparent.isTransparentKeyword = true;
        return transparent;
    }
};

function toHex(v) {
    return '#' + v.map(function (c) {
        c = clamp(Math.round(c), 255);
        return (c < 16 ? '0' : '') + c.toString(16);
    }).join('');
}

function clamp(v, max) {
    return Math.min(Math.max(v, 0), max); 
}

})(require('../tree'));

(function (tree) {

tree.Comment = function (value, silent, index, currentFileInfo) {
    this.value = value;
    this.silent = !!silent;
    this.currentFileInfo = currentFileInfo;
};
tree.Comment.prototype = {
    type: "Comment",
    genCSS: function (env, output) {
        if (this.debugInfo) {
            output.add(tree.debugInfo(env, this), this.currentFileInfo, this.index);
        }
        output.add(this.value.trim()); //TODO shouldn't need to trim, we shouldn't grab the \n
    },
    toCSS: tree.toCSS,
    isSilent: function(env) {
        var isReference = (this.currentFileInfo && this.currentFileInfo.reference && !this.isReferenced),
            isCompressed = env.compress && !this.value.match(/^\/\*!/);
        return this.silent || isReference || isCompressed;
    },
    eval: function () { return this; },
    markReferenced: function () {
        this.isReferenced = true;
    }
};

})(require('../tree'));

(function (tree) {

tree.Condition = function (op, l, r, i, negate) {
    this.op = op.trim();
    this.lvalue = l;
    this.rvalue = r;
    this.index = i;
    this.negate = negate;
};
tree.Condition.prototype = {
    type: "Condition",
    accept: function (visitor) {
        this.lvalue = visitor.visit(this.lvalue);
        this.rvalue = visitor.visit(this.rvalue);
    },
    eval: function (env) {
        var a = this.lvalue.eval(env),
            b = this.rvalue.eval(env);

        var i = this.index, result;

        result = (function (op) {
            switch (op) {
                case 'and':
                    return a && b;
                case 'or':
                    return a || b;
                default:
                    if (a.compare) {
                        result = a.compare(b);
                    } else if (b.compare) {
                        result = b.compare(a);
                    } else {
                        throw { type: "Type",
                                message: "Unable to perform comparison",
                                index: i };
                    }
                    switch (result) {
                        case -1: return op === '<' || op === '=<' || op === '<=';
                        case  0: return op === '=' || op === '>=' || op === '=<' || op === '<=';
                        case  1: return op === '>' || op === '>=';
                    }
            }
        })(this.op);
        return this.negate ? !result : result;
    }
};

})(require('../tree'));

(function (tree) {

//
// A number with a unit
//
tree.Dimension = function (value, unit) {
    this.value = parseFloat(value);
    this.unit = (unit && unit instanceof tree.Unit) ? unit :
      new(tree.Unit)(unit ? [unit] : undefined);
};

tree.Dimension.prototype = {
    type: "Dimension",
    accept: function (visitor) {
        this.unit = visitor.visit(this.unit);
    },
    eval: function (env) {
        return this;
    },
    toColor: function () {
        return new(tree.Color)([this.value, this.value, this.value]);
    },
    genCSS: function (env, output) {
        if ((env && env.strictUnits) && !this.unit.isSingular()) {
            throw new Error("Multiple units in dimension. Correct the units or use the unit function. Bad unit: "+this.unit.toString());
        }

        var value = this.value,
            strValue = String(value);

        if (value !== 0 && value < 0.000001 && value > -0.000001) {
            // would be output 1e-6 etc.
            strValue = value.toFixed(20).replace(/0+$/, "");
        }

        if (env && env.compress) {
            // Zero values doesn't need a unit
            if (value === 0 && this.unit.isLength()) {
                output.add(strValue);
                return;
            }

            // Float values doesn't need a leading zero
            if (value > 0 && value < 1) {
                strValue = (strValue).substr(1);
            }
        }

        output.add(strValue);
        this.unit.genCSS(env, output);
    },
    toCSS: tree.toCSS,

    // In an operation between two Dimensions,
    // we default to the first Dimension's unit,
    // so `1px + 2` will yield `3px`.
    operate: function (env, op, other) {
        /*jshint noempty:false */
        var value = tree.operate(env, op, this.value, other.value),
            unit = this.unit.clone();

        if (op === '+' || op === '-') {
            if (unit.numerator.length === 0 && unit.denominator.length === 0) {
                unit.numerator = other.unit.numerator.slice(0);
                unit.denominator = other.unit.denominator.slice(0);
            } else if (other.unit.numerator.length === 0 && unit.denominator.length === 0) {
                // do nothing
            } else {
                other = other.convertTo(this.unit.usedUnits());

                if(env.strictUnits && other.unit.toString() !== unit.toString()) {
                  throw new Error("Incompatible units. Change the units or use the unit function. Bad units: '" + unit.toString() +
                    "' and '" + other.unit.toString() + "'.");
                }

                value = tree.operate(env, op, this.value, other.value);
            }
        } else if (op === '*') {
            unit.numerator = unit.numerator.concat(other.unit.numerator).sort();
            unit.denominator = unit.denominator.concat(other.unit.denominator).sort();
            unit.cancel();
        } else if (op === '/') {
            unit.numerator = unit.numerator.concat(other.unit.denominator).sort();
            unit.denominator = unit.denominator.concat(other.unit.numerator).sort();
            unit.cancel();
        }
        return new(tree.Dimension)(value, unit);
    },

    compare: function (other) {
        if (other instanceof tree.Dimension) {
            var a = this.unify(), b = other.unify(),
                aValue = a.value, bValue = b.value;

            if (bValue > aValue) {
                return -1;
            } else if (bValue < aValue) {
                return 1;
            } else {
                if (!b.unit.isEmpty() && a.unit.compare(b.unit) !== 0) {
                    return -1;
                }
                return 0;
            }
        } else {
            return -1;
        }
    },

    unify: function () {
        return this.convertTo({ length: 'm', duration: 's', angle: 'rad' });
    },

    convertTo: function (conversions) {
        var value = this.value, unit = this.unit.clone(),
            i, groupName, group, targetUnit, derivedConversions = {}, applyUnit;

        if (typeof conversions === 'string') {
            for(i in tree.UnitConversions) {
                if (tree.UnitConversions[i].hasOwnProperty(conversions)) {
                    derivedConversions = {};
                    derivedConversions[i] = conversions;
                }
            }
            conversions = derivedConversions;
        }
        applyUnit = function (atomicUnit, denominator) {
          /*jshint loopfunc:true */
            if (group.hasOwnProperty(atomicUnit)) {
                if (denominator) {
                    value = value / (group[atomicUnit] / group[targetUnit]);
                } else {
                    value = value * (group[atomicUnit] / group[targetUnit]);
                }

                return targetUnit;
            }

            return atomicUnit;
        };

        for (groupName in conversions) {
            if (conversions.hasOwnProperty(groupName)) {
                targetUnit = conversions[groupName];
                group = tree.UnitConversions[groupName];

                unit.map(applyUnit);
            }
        }

        unit.cancel();

        return new(tree.Dimension)(value, unit);
    }
};

// http://www.w3.org/TR/css3-values/#absolute-lengths
tree.UnitConversions = {
    length: {
         'm': 1,
        'cm': 0.01,
        'mm': 0.001,
        'in': 0.0254,
        'pt': 0.0254 / 72,
        'pc': 0.0254 / 72 * 12
    },
    duration: {
        's': 1,
        'ms': 0.001
    },
    angle: {
        'rad': 1/(2*Math.PI),
        'deg': 1/360,
        'grad': 1/400,
        'turn': 1
    }
};

tree.Unit = function (numerator, denominator, backupUnit) {
    this.numerator = numerator ? numerator.slice(0).sort() : [];
    this.denominator = denominator ? denominator.slice(0).sort() : [];
    this.backupUnit = backupUnit;
};

tree.Unit.prototype = {
    type: "Unit",
    clone: function () {
        return new tree.Unit(this.numerator.slice(0), this.denominator.slice(0), this.backupUnit);
    },
    genCSS: function (env, output) {
        if (this.numerator.length >= 1) {
            output.add(this.numerator[0]);
        } else
        if (this.denominator.length >= 1) {
            output.add(this.denominator[0]);
        } else
        if ((!env || !env.strictUnits) && this.backupUnit) {
            output.add(this.backupUnit);
        }
    },
    toCSS: tree.toCSS,

    toString: function () {
      var i, returnStr = this.numerator.join("*");
      for (i = 0; i < this.denominator.length; i++) {
          returnStr += "/" + this.denominator[i];
      }
      return returnStr;
    },

    compare: function (other) {
        return this.is(other.toString()) ? 0 : -1;
    },

    is: function (unitString) {
        return this.toString() === unitString;
    },

    isLength: function () {
        return Boolean(this.toCSS().match(/px|em|%|in|cm|mm|pc|pt|ex/));
    },

    isEmpty: function () {
        return this.numerator.length === 0 && this.denominator.length === 0;
    },

    isSingular: function() {
        return this.numerator.length <= 1 && this.denominator.length === 0;
    },

    map: function(callback) {
        var i;

        for (i = 0; i < this.numerator.length; i++) {
            this.numerator[i] = callback(this.numerator[i], false);
        }

        for (i = 0; i < this.denominator.length; i++) {
            this.denominator[i] = callback(this.denominator[i], true);
        }
    },

    usedUnits: function() {
        var group, result = {}, mapUnit;

        mapUnit = function (atomicUnit) {
        /*jshint loopfunc:true */
            if (group.hasOwnProperty(atomicUnit) && !result[groupName]) {
                result[groupName] = atomicUnit;
            }

            return atomicUnit;
        };

        for (var groupName in tree.UnitConversions) {
            if (tree.UnitConversions.hasOwnProperty(groupName)) {
                group = tree.UnitConversions[groupName];

                this.map(mapUnit);
            }
        }

        return result;
    },

    cancel: function () {
        var counter = {}, atomicUnit, i, backup;

        for (i = 0; i < this.numerator.length; i++) {
            atomicUnit = this.numerator[i];
            if (!backup) {
                backup = atomicUnit;
            }
            counter[atomicUnit] = (counter[atomicUnit] || 0) + 1;
        }

        for (i = 0; i < this.denominator.length; i++) {
            atomicUnit = this.denominator[i];
            if (!backup) {
                backup = atomicUnit;
            }
            counter[atomicUnit] = (counter[atomicUnit] || 0) - 1;
        }

        this.numerator = [];
        this.denominator = [];

        for (atomicUnit in counter) {
            if (counter.hasOwnProperty(atomicUnit)) {
                var count = counter[atomicUnit];

                if (count > 0) {
                    for (i = 0; i < count; i++) {
                        this.numerator.push(atomicUnit);
                    }
                } else if (count < 0) {
                    for (i = 0; i < -count; i++) {
                        this.denominator.push(atomicUnit);
                    }
                }
            }
        }

        if (this.numerator.length === 0 && this.denominator.length === 0 && backup) {
            this.backupUnit = backup;
        }

        this.numerator.sort();
        this.denominator.sort();
    }
};

})(require('../tree'));

(function (tree) {

tree.Directive = function (name, value, index, currentFileInfo) {
    this.name = name;

    if (Array.isArray(value)) {
        this.rules = [new(tree.Ruleset)(null, value)];
        this.rules[0].allowImports = true;
    } else {
        this.value = value;
    }
    this.index = index;
    this.currentFileInfo = currentFileInfo;

};
tree.Directive.prototype = {
    type: "Directive",
    accept: function (visitor) {
        if (this.rules) {
            this.rules = visitor.visitArray(this.rules);
        }
        if (this.value) {
            this.value = visitor.visit(this.value);
        }
    },
    genCSS: function (env, output) {
        output.add(this.name, this.currentFileInfo, this.index);
        if (this.rules) {
            tree.outputRuleset(env, output, this.rules);
        } else {
            output.add(' ');
            this.value.genCSS(env, output);
            output.add(';');
        }
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        var evaldDirective = this;
        if (this.rules) {
            env.frames.unshift(this);
            evaldDirective = new(tree.Directive)(this.name, null, this.index, this.currentFileInfo);
            evaldDirective.rules = [this.rules[0].eval(env)];
            evaldDirective.rules[0].root = true;
            env.frames.shift();
        }
        return evaldDirective;
    },
    variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
    find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
    rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
    markReferenced: function () {
        var i, rules;
        this.isReferenced = true;
        if (this.rules) {
            rules = this.rules[0].rules;
            for (i = 0; i < rules.length; i++) {
                if (rules[i].markReferenced) {
                    rules[i].markReferenced();
                }
            }
        }
    }
};

})(require('../tree'));

(function (tree) {

tree.Element = function (combinator, value, index, currentFileInfo) {
    this.combinator = combinator instanceof tree.Combinator ?
                      combinator : new(tree.Combinator)(combinator);

    if (typeof(value) === 'string') {
        this.value = value.trim();
    } else if (value) {
        this.value = value;
    } else {
        this.value = "";
    }
    this.index = index;
    this.currentFileInfo = currentFileInfo;
};
tree.Element.prototype = {
    type: "Element",
    accept: function (visitor) {
        var value = this.value;
        this.combinator = visitor.visit(this.combinator);
        if (typeof value === "object") {
            this.value = visitor.visit(value);
        }
    },
    eval: function (env) {
        return new(tree.Element)(this.combinator,
                                 this.value.eval ? this.value.eval(env) : this.value,
                                 this.index,
                                 this.currentFileInfo);
    },
    genCSS: function (env, output) {
        output.add(this.toCSS(env), this.currentFileInfo, this.index);
    },
    toCSS: function (env) {
        var value = (this.value.toCSS ? this.value.toCSS(env) : this.value);
        if (value === '' && this.combinator.value.charAt(0) === '&') {
            return '';
        } else {
            return this.combinator.toCSS(env || {}) + value;
        }
    }
};

tree.Attribute = function (key, op, value) {
    this.key = key;
    this.op = op;
    this.value = value;
};
tree.Attribute.prototype = {
    type: "Attribute",
    eval: function (env) {
        return new(tree.Attribute)(this.key.eval ? this.key.eval(env) : this.key,
            this.op, (this.value && this.value.eval) ? this.value.eval(env) : this.value);
    },
    genCSS: function (env, output) {
        output.add(this.toCSS(env));
    },
    toCSS: function (env) {
        var value = this.key.toCSS ? this.key.toCSS(env) : this.key;

        if (this.op) {
            value += this.op;
            value += (this.value.toCSS ? this.value.toCSS(env) : this.value);
        }

        return '[' + value + ']';
    }
};

tree.Combinator = function (value) {
    if (value === ' ') {
        this.value = ' ';
    } else {
        this.value = value ? value.trim() : "";
    }
};
tree.Combinator.prototype = {
    type: "Combinator",
    _outputMap: {
        ''  : '',
        ' ' : ' ',
        ':' : ' :',
        '+' : ' + ',
        '~' : ' ~ ',
        '>' : ' > ',
        '|' : '|',
        '^' : ' ^ ',
        '^^' : ' ^^ '
    },
    _outputMapCompressed: {
        ''  : '',
        ' ' : ' ',
        ':' : ' :',
        '+' : '+',
        '~' : '~',
        '>' : '>',
        '|' : '|',
        '^' : '^',
        '^^' : '^^'
    },
    genCSS: function (env, output) {
        output.add((env.compress ? this._outputMapCompressed : this._outputMap)[this.value]);
    },
    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {

tree.Expression = function (value) { this.value = value; };
tree.Expression.prototype = {
    type: "Expression",
    accept: function (visitor) {
        if (this.value) {
            this.value = visitor.visitArray(this.value);
        }
    },
    eval: function (env) {
        var returnValue,
            inParenthesis = this.parens && !this.parensInOp,
            doubleParen = false;
        if (inParenthesis) {
            env.inParenthesis();
        }
        if (this.value.length > 1) {
            returnValue = new(tree.Expression)(this.value.map(function (e) {
                return e.eval(env);
            }));
        } else if (this.value.length === 1) {
            if (this.value[0].parens && !this.value[0].parensInOp) {
                doubleParen = true;
            }
            returnValue = this.value[0].eval(env);
        } else {
            returnValue = this;
        }
        if (inParenthesis) {
            env.outOfParenthesis();
        }
        if (this.parens && this.parensInOp && !(env.isMathOn()) && !doubleParen) {
            returnValue = new(tree.Paren)(returnValue);
        }
        return returnValue;
    },
    genCSS: function (env, output) {
        for(var i = 0; i < this.value.length; i++) {
            this.value[i].genCSS(env, output);
            if (i + 1 < this.value.length) {
                output.add(" ");
            }
        }
    },
    toCSS: tree.toCSS,
    throwAwayComments: function () {
        this.value = this.value.filter(function(v) {
            return !(v instanceof tree.Comment);
        });
    }
};

})(require('../tree'));

(function (tree) {

tree.Extend = function Extend(selector, option, index) {
    this.selector = selector;
    this.option = option;
    this.index = index;
    this.object_id = tree.Extend.next_id++;
    this.parent_ids = [this.object_id];

    switch(option) {
        case "all":
            this.allowBefore = true;
            this.allowAfter = true;
        break;
        default:
            this.allowBefore = false;
            this.allowAfter = false;
        break;
    }
};
tree.Extend.next_id = 0;

tree.Extend.prototype = {
    type: "Extend",
    accept: function (visitor) {
        this.selector = visitor.visit(this.selector);
    },
    eval: function (env) {
        return new(tree.Extend)(this.selector.eval(env), this.option, this.index);
    },
    clone: function (env) {
        return new(tree.Extend)(this.selector, this.option, this.index);
    },
    findSelfSelectors: function (selectors) {
        var selfElements = [],
            i,
            selectorElements;

        for(i = 0; i < selectors.length; i++) {
            selectorElements = selectors[i].elements;
            // duplicate the logic in genCSS function inside the selector node.
            // future TODO - move both logics into the selector joiner visitor
            if (i > 0 && selectorElements.length && selectorElements[0].combinator.value === "") {
                selectorElements[0].combinator.value = ' ';
            }
            selfElements = selfElements.concat(selectors[i].elements);
        }

        this.selfSelectors = [{ elements: selfElements }];
    }
};

})(require('../tree'));

(function (tree) {
//
// CSS @import node
//
// The general strategy here is that we don't want to wait
// for the parsing to be completed, before we start importing
// the file. That's because in the context of a browser,
// most of the time will be spent waiting for the server to respond.
//
// On creation, we push the import path to our import queue, though
// `import,push`, we also pass it a callback, which it'll call once
// the file has been fetched, and parsed.
//
tree.Import = function (path, features, options, index, currentFileInfo) {
    this.options = options;
    this.index = index;
    this.path = path;
    this.features = features;
    this.currentFileInfo = currentFileInfo;

    if (this.options.less !== undefined || this.options.inline) {
        this.css = !this.options.less || this.options.inline;
    } else {
        var pathValue = this.getPath();
        if (pathValue && /css([\?;].*)?$/.test(pathValue)) {
            this.css = true;
        }
    }
};

//
// The actual import node doesn't return anything, when converted to CSS.
// The reason is that it's used at the evaluation stage, so that the rules
// it imports can be treated like any other rules.
//
// In `eval`, we make sure all Import nodes get evaluated, recursively, so
// we end up with a flat structure, which can easily be imported in the parent
// ruleset.
//
tree.Import.prototype = {
    type: "Import",
    accept: function (visitor) {
        if (this.features) {
            this.features = visitor.visit(this.features);
        }
        this.path = visitor.visit(this.path);
        if (!this.options.inline && this.root) {
            this.root = visitor.visit(this.root);
        }
    },
    genCSS: function (env, output) {
        if (this.css) {
            output.add("@import ", this.currentFileInfo, this.index);
            this.path.genCSS(env, output);
            if (this.features) {
                output.add(" ");
                this.features.genCSS(env, output);
            }
            output.add(';');
        }
    },
    toCSS: tree.toCSS,
    getPath: function () {
        if (this.path instanceof tree.Quoted) {
            var path = this.path.value;
            return (this.css !== undefined || /(\.[a-z]*$)|([\?;].*)$/.test(path)) ? path : path + '.less';
        } else if (this.path instanceof tree.URL) {
            return this.path.value.value;
        }
        return null;
    },
    evalForImport: function (env) {
        return new(tree.Import)(this.path.eval(env), this.features, this.options, this.index, this.currentFileInfo);
    },
    evalPath: function (env) {
        var path = this.path.eval(env);
        var rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;

        if (!(path instanceof tree.URL)) {
            if (rootpath) {
                var pathValue = path.value;
                // Add the base path if the import is relative
                if (pathValue && env.isPathRelative(pathValue)) {
                    path.value = rootpath + pathValue;
                }
            }
            path.value = env.normalizePath(path.value);
        }

        return path;
    },
    eval: function (env) {
        var ruleset, features = this.features && this.features.eval(env);

        if (this.skip) { return []; }

        if (this.options.inline) {
            //todo needs to reference css file not import
            var contents = new(tree.Anonymous)(this.root, 0, {filename: this.importedFilename}, true);
            return this.features ? new(tree.Media)([contents], this.features.value) : [contents];
        } else if (this.css) {
            var newImport = new(tree.Import)(this.evalPath(env), features, this.options, this.index);
            if (!newImport.css && this.error) {
                throw this.error;
            }
            return newImport;
        } else {
            ruleset = new(tree.Ruleset)(null, this.root.rules.slice(0));

            ruleset.evalImports(env);

            return this.features ? new(tree.Media)(ruleset.rules, this.features.value) : ruleset.rules;
        }
    }
};

})(require('../tree'));

(function (tree) {

tree.JavaScript = function (string, index, escaped) {
    this.escaped = escaped;
    this.expression = string;
    this.index = index;
};
tree.JavaScript.prototype = {
    type: "JavaScript",
    eval: function (env) {
        var result,
            that = this,
            context = {};

        var expression = this.expression.replace(/@\{([\w-]+)\}/g, function (_, name) {
            return tree.jsify(new(tree.Variable)('@' + name, that.index).eval(env));
        });

        try {
            expression = new(Function)('return (' + expression + ')');
        } catch (e) {
            throw { message: "JavaScript evaluation error: " + e.message + " from `" + expression + "`" ,
                    index: this.index };
        }

        var variables = env.frames[0].variables();
        for (var k in variables) {
            if (variables.hasOwnProperty(k)) {
                /*jshint loopfunc:true */
                context[k.slice(1)] = {
                    value: variables[k].value,
                    toJS: function () {
                        return this.value.eval(env).toCSS();
                    }
                };
            }
        }

        try {
            result = expression.call(context);
        } catch (e) {
            throw { message: "JavaScript evaluation error: '" + e.name + ': ' + e.message + "'" ,
                    index: this.index };
        }
        if (typeof(result) === 'number') {
            return new(tree.Dimension)(result);
        } else if (typeof(result) === 'string') {
            return new(tree.Quoted)('"' + result + '"', result, this.escaped, this.index);
        } else if (Array.isArray(result)) {
            return new(tree.Anonymous)(result.join(', '));
        } else {
            return new(tree.Anonymous)(result);
        }
    }
};

})(require('../tree'));


(function (tree) {

tree.Keyword = function (value) { this.value = value; };
tree.Keyword.prototype = {
    type: "Keyword",
    eval: function () { return this; },
    genCSS: function (env, output) {
        output.add(this.value);
    },
    toCSS: tree.toCSS,
    compare: function (other) {
        if (other instanceof tree.Keyword) {
            return other.value === this.value ? 0 : 1;
        } else {
            return -1;
        }
    }
};

tree.True = new(tree.Keyword)('true');
tree.False = new(tree.Keyword)('false');

})(require('../tree'));

(function (tree) {

tree.Media = function (value, features, index, currentFileInfo) {
    this.index = index;
    this.currentFileInfo = currentFileInfo;

    var selectors = this.emptySelectors();

    this.features = new(tree.Value)(features);
    this.rules = [new(tree.Ruleset)(selectors, value)];
    this.rules[0].allowImports = true;
};
tree.Media.prototype = {
    type: "Media",
    accept: function (visitor) {
        if (this.features) {
            this.features = visitor.visit(this.features);
        }
        if (this.rules) {
            this.rules = visitor.visitArray(this.rules);
        }
    },
    genCSS: function (env, output) {
        output.add('@media ', this.currentFileInfo, this.index);
        this.features.genCSS(env, output);
        tree.outputRuleset(env, output, this.rules);
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        if (!env.mediaBlocks) {
            env.mediaBlocks = [];
            env.mediaPath = [];
        }
        
        var media = new(tree.Media)(null, [], this.index, this.currentFileInfo);
        if(this.debugInfo) {
            this.rules[0].debugInfo = this.debugInfo;
            media.debugInfo = this.debugInfo;
        }
        var strictMathBypass = false;
        if (!env.strictMath) {
            strictMathBypass = true;
            env.strictMath = true;
        }
        try {
            media.features = this.features.eval(env);
        }
        finally {
            if (strictMathBypass) {
                env.strictMath = false;
            }
        }
        
        env.mediaPath.push(media);
        env.mediaBlocks.push(media);
        
        env.frames.unshift(this.rules[0]);
        media.rules = [this.rules[0].eval(env)];
        env.frames.shift();
        
        env.mediaPath.pop();

        return env.mediaPath.length === 0 ? media.evalTop(env) :
                    media.evalNested(env);
    },
    variable: function (name) { return tree.Ruleset.prototype.variable.call(this.rules[0], name); },
    find: function () { return tree.Ruleset.prototype.find.apply(this.rules[0], arguments); },
    rulesets: function () { return tree.Ruleset.prototype.rulesets.apply(this.rules[0]); },
    emptySelectors: function() { 
        var el = new(tree.Element)('', '&', this.index, this.currentFileInfo);
        return [new(tree.Selector)([el], null, null, this.index, this.currentFileInfo)];
    },
    markReferenced: function () {
        var i, rules = this.rules[0].rules;
        this.isReferenced = true;
        for (i = 0; i < rules.length; i++) {
            if (rules[i].markReferenced) {
                rules[i].markReferenced();
            }
        }
    },

    evalTop: function (env) {
        var result = this;

        // Render all dependent Media blocks.
        if (env.mediaBlocks.length > 1) {
            var selectors = this.emptySelectors();
            result = new(tree.Ruleset)(selectors, env.mediaBlocks);
            result.multiMedia = true;
        }

        delete env.mediaBlocks;
        delete env.mediaPath;

        return result;
    },
    evalNested: function (env) {
        var i, value,
            path = env.mediaPath.concat([this]);

        // Extract the media-query conditions separated with `,` (OR).
        for (i = 0; i < path.length; i++) {
            value = path[i].features instanceof tree.Value ?
                        path[i].features.value : path[i].features;
            path[i] = Array.isArray(value) ? value : [value];
        }

        // Trace all permutations to generate the resulting media-query.
        //
        // (a, b and c) with nested (d, e) ->
        //    a and d
        //    a and e
        //    b and c and d
        //    b and c and e
        this.features = new(tree.Value)(this.permute(path).map(function (path) {
            path = path.map(function (fragment) {
                return fragment.toCSS ? fragment : new(tree.Anonymous)(fragment);
            });

            for(i = path.length - 1; i > 0; i--) {
                path.splice(i, 0, new(tree.Anonymous)("and"));
            }

            return new(tree.Expression)(path);
        }));

        // Fake a tree-node that doesn't output anything.
        return new(tree.Ruleset)([], []);
    },
    permute: function (arr) {
      if (arr.length === 0) {
          return [];
      } else if (arr.length === 1) {
          return arr[0];
      } else {
          var result = [];
          var rest = this.permute(arr.slice(1));
          for (var i = 0; i < rest.length; i++) {
              for (var j = 0; j < arr[0].length; j++) {
                  result.push([arr[0][j]].concat(rest[i]));
              }
          }
          return result;
      }
    },
    bubbleSelectors: function (selectors) {
      this.rules = [new(tree.Ruleset)(selectors.slice(0), [this.rules[0]])];
    }
};

})(require('../tree'));

(function (tree) {

tree.mixin = {};
tree.mixin.Call = function (elements, args, index, currentFileInfo, important) {
    this.selector = new(tree.Selector)(elements);
    this.arguments = (args && args.length) ? args : null;
    this.index = index;
    this.currentFileInfo = currentFileInfo;
    this.important = important;
};
tree.mixin.Call.prototype = {
    type: "MixinCall",
    accept: function (visitor) {
        if (this.selector) {
            this.selector = visitor.visit(this.selector);
        }
        if (this.arguments) {
            this.arguments = visitor.visitArray(this.arguments);
        }
    },
    eval: function (env) {
        var mixins, mixin, args, rules = [], match = false, i, m, f, isRecursive, isOneFound, rule;
        var candidates = [], candidate, conditionResult = [], defaultFunc = tree.defaultFunc, defaultUsed = false; 

        args = this.arguments && this.arguments.map(function (a) {
            return { name: a.name, value: a.value.eval(env) };
        });

        for (i = 0; i < env.frames.length; i++) {
            if ((mixins = env.frames[i].find(this.selector)).length > 0) {
                isOneFound = true;
                
                // To make `default()` function independent of definition order we have two "subpasses" here.
                // At first we evaluate each guard *twice* (with `default() == true` and `default() == false`),
                // and build candidate list with corresponding flags. Then, when we know all possible matches,
                // we make a final decision.
                
                for (m = 0; m < mixins.length; m++) {
                    mixin = mixins[m];
                    isRecursive = false;
                    for(f = 0; f < env.frames.length; f++) {
                        if ((!(mixin instanceof tree.mixin.Definition)) && mixin === (env.frames[f].originalRuleset || env.frames[f])) {
                            isRecursive = true;
                            break;
                        }
                    }
                    if (isRecursive) {
                        continue;
                    }
                    
                    if (mixin.matchArgs(args, env)) {  
                        candidate = {mixin: mixin};
                        
                        if (mixin.matchCondition) { 
                            for (f = 0; f < 2; f++) {
                                defaultFunc.value(f);
                                conditionResult[f] = mixin.matchCondition(args, env);
                            }
                            if (conditionResult[0] || conditionResult[1]) {
                                if (conditionResult[0] != conditionResult[1]) {
                                    if (defaultUsed) {
                                        // todo: ideally, it would make sense to also print the candidate 
                                        // mixin definitions that cause the conflict (current one and the
                                        // mixin that set defaultUsed flag). But is there any easy method 
                                        // to get their filename/line/index info here?
                                        throw { type: 'Runtime',
                                            message: 'Ambiguous use of `default()` found when matching for `'
                                                + this.format(args) + '`',
                                            index: this.index, filename: this.currentFileInfo.filename };
                                    }
                                    
                                    defaultUsed                   = true;
                                    candidate.matchIfDefault      = true;
                                    candidate.matchIfDefaultValue = conditionResult[1];
                                }

                                candidates.push(candidate);
                            }   
                        }
                        else {
                            candidates.push(candidate);
                        }
                        
                        match = true;
                    }
                }
                
                defaultFunc.reset();
                
                for (m = 0; m < candidates.length; m++) {
                    candidate = candidates[m];
                    if (!candidate.matchIfDefault || (candidate.matchIfDefaultValue == (candidates.length == 1))) {
                        try {
                            mixin = candidate.mixin;
                            if (!(mixin instanceof tree.mixin.Definition)) {
                                mixin = new tree.mixin.Definition("", [], mixin.rules, null, false);
                                mixin.originalRuleset = mixins[m].originalRuleset || mixins[m];
                            }
                            //if (this.important) {
                            //    isImportant = env.isImportant;
                            //    env.isImportant = true;
                            //}
                            Array.prototype.push.apply(
                                  rules, mixin.eval(env, args, this.important).rules);
                            //if (this.important) {
                            //    env.isImportant = isImportant;
                            //}
                        } catch (e) {
                            throw { message: e.message, index: this.index, filename: this.currentFileInfo.filename, stack: e.stack };
                        }
                    }
                }
                
                if (match) {
                    if (!this.currentFileInfo || !this.currentFileInfo.reference) {
                        for (i = 0; i < rules.length; i++) {
                            rule = rules[i];
                            if (rule.markReferenced) {
                                rule.markReferenced();
                            }
                        }
                    }
                    return rules;
                }
            }
        }
        if (isOneFound) {
            throw { type:    'Runtime',
                    message: 'No matching definition was found for `' + this.format(args) + '`',
                    index:   this.index, filename: this.currentFileInfo.filename };
        } else {
            throw { type:    'Name',
                    message: this.selector.toCSS().trim() + " is undefined",
                    index:   this.index, filename: this.currentFileInfo.filename };
        }
    },
    format: function (args) {
        return this.selector.toCSS().trim() + '(' +
            (args ? args.map(function (a) {
                var argValue = "";
                if (a.name) {
                    argValue += a.name + ":";
                }
                if (a.value.toCSS) {
                    argValue += a.value.toCSS();
                } else {
                    argValue += "???";
                }
                return argValue;
            }).join(', ') : "") + ")";
    }
};

tree.mixin.Definition = function (name, params, rules, condition, variadic) {
    this.name = name;
    this.selectors = [new(tree.Selector)([new(tree.Element)(null, name, this.index, this.currentFileInfo)])];
    this.params = params;
    this.condition = condition;
    this.variadic = variadic;
    this.arity = params.length;
    this.rules = rules;
    this._lookups = {};
    this.required = params.reduce(function (count, p) {
        if (!p.name || (p.name && !p.value)) { return count + 1; }
        else                                 { return count; }
    }, 0);
    this.parent = tree.Ruleset.prototype;
    this.frames = [];
};
tree.mixin.Definition.prototype = {
    type: "MixinDefinition",
    accept: function (visitor) {
        if (this.params && this.params.length) {
            this.params = visitor.visitArray(this.params);
        }
        this.rules = visitor.visitArray(this.rules);
        if (this.condition) {
            this.condition = visitor.visit(this.condition);
        }
    },
    variable:  function (name) { return this.parent.variable.call(this, name); },
    variables: function ()     { return this.parent.variables.call(this); },
    find:      function ()     { return this.parent.find.apply(this, arguments); },
    rulesets:  function ()     { return this.parent.rulesets.apply(this); },

    evalParams: function (env, mixinEnv, args, evaldArguments) {
        /*jshint boss:true */
        var frame = new(tree.Ruleset)(null, null),
            varargs, arg,
            params = this.params.slice(0),
            i, j, val, name, isNamedFound, argIndex;

        mixinEnv = new tree.evalEnv(mixinEnv, [frame].concat(mixinEnv.frames));

        if (args) {
            args = args.slice(0);

            for(i = 0; i < args.length; i++) {
                arg = args[i];
                if (name = (arg && arg.name)) {
                    isNamedFound = false;
                    for(j = 0; j < params.length; j++) {
                        if (!evaldArguments[j] && name === params[j].name) {
                            evaldArguments[j] = arg.value.eval(env);
                            frame.prependRule(new(tree.Rule)(name, arg.value.eval(env)));
                            isNamedFound = true;
                            break;
                        }
                    }
                    if (isNamedFound) {
                        args.splice(i, 1);
                        i--;
                        continue;
                    } else {
                        throw { type: 'Runtime', message: "Named argument for " + this.name +
                            ' ' + args[i].name + ' not found' };
                    }
                }
            }
        }
        argIndex = 0;
        for (i = 0; i < params.length; i++) {
            if (evaldArguments[i]) { continue; }

            arg = args && args[argIndex];

            if (name = params[i].name) {
                if (params[i].variadic && args) {
                    varargs = [];
                    for (j = argIndex; j < args.length; j++) {
                        varargs.push(args[j].value.eval(env));
                    }
                    frame.prependRule(new(tree.Rule)(name, new(tree.Expression)(varargs).eval(env)));
                } else {
                    val = arg && arg.value;
                    if (val) {
                        val = val.eval(env);
                    } else if (params[i].value) {
                        val = params[i].value.eval(mixinEnv);
                        frame.resetCache();
                    } else {
                        throw { type: 'Runtime', message: "wrong number of arguments for " + this.name +
                            ' (' + args.length + ' for ' + this.arity + ')' };
                    }
                    
                    frame.prependRule(new(tree.Rule)(name, val));
                    evaldArguments[i] = val;
                }
            }

            if (params[i].variadic && args) {
                for (j = argIndex; j < args.length; j++) {
                    evaldArguments[j] = args[j].value.eval(env);
                }
            }
            argIndex++;
        }

        return frame;
    },
    eval: function (env, args, important) {
        var _arguments = [],
            mixinFrames = this.frames.concat(env.frames),
            frame = this.evalParams(env, new(tree.evalEnv)(env, mixinFrames), args, _arguments),
            rules, ruleset;

        frame.prependRule(new(tree.Rule)('@arguments', new(tree.Expression)(_arguments).eval(env)));

        rules = this.rules.slice(0);

        ruleset = new(tree.Ruleset)(null, rules);
        ruleset.originalRuleset = this;
        ruleset = ruleset.eval(new(tree.evalEnv)(env, [this, frame].concat(mixinFrames)));
        if (important) {
            ruleset = this.parent.makeImportant.apply(ruleset);
        }
        return ruleset;
    },
    matchCondition: function (args, env) {
        if (this.condition && !this.condition.eval(
            new(tree.evalEnv)(env,
                [this.evalParams(env, new(tree.evalEnv)(env, this.frames.concat(env.frames)), args, [])] // the parameter variables
                    .concat(this.frames) // the parent namespace/mixin frames
                    .concat(env.frames)))) { // the current environment frames
            return false;
        }
        return true;
    },
    matchArgs: function (args, env) {
        var argsLength = (args && args.length) || 0, len;

        if (! this.variadic) {
            if (argsLength < this.required)                               { return false; }
            if (argsLength > this.params.length)                          { return false; }
        } else {
            if (argsLength < (this.required - 1))                         { return false; }
        }

        len = Math.min(argsLength, this.arity);

        for (var i = 0; i < len; i++) {
            if (!this.params[i].name && !this.params[i].variadic) {
                if (args[i].value.eval(env).toCSS() != this.params[i].value.eval(env).toCSS()) {
                    return false;
                }
            }
        }
        return true;
    }
};

})(require('../tree'));

(function (tree) {

tree.Negative = function (node) {
    this.value = node;
};
tree.Negative.prototype = {
    type: "Negative",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    genCSS: function (env, output) {
        output.add('-');
        this.value.genCSS(env, output);
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        if (env.isMathOn()) {
            return (new(tree.Operation)('*', [new(tree.Dimension)(-1), this.value])).eval(env);
        }
        return new(tree.Negative)(this.value.eval(env));
    }
};

})(require('../tree'));

(function (tree) {

tree.Operation = function (op, operands, isSpaced) {
    this.op = op.trim();
    this.operands = operands;
    this.isSpaced = isSpaced;
};
tree.Operation.prototype = {
    type: "Operation",
    accept: function (visitor) {
        this.operands = visitor.visit(this.operands);
    },
    eval: function (env) {
        var a = this.operands[0].eval(env),
            b = this.operands[1].eval(env);

        if (env.isMathOn()) {
            if (a instanceof tree.Dimension && b instanceof tree.Color) {
                a = a.toColor();
            }
            if (b instanceof tree.Dimension && a instanceof tree.Color) {
                b = b.toColor();
            }
            if (!a.operate) {
                throw { type: "Operation",
                        message: "Operation on an invalid type" };
            }

            return a.operate(env, this.op, b);
        } else {
            return new(tree.Operation)(this.op, [a, b], this.isSpaced);
        }
    },
    genCSS: function (env, output) {
        this.operands[0].genCSS(env, output);
        if (this.isSpaced) {
            output.add(" ");
        }
        output.add(this.op);
        if (this.isSpaced) {
            output.add(" ");
        }
        this.operands[1].genCSS(env, output);
    },
    toCSS: tree.toCSS
};

tree.operate = function (env, op, a, b) {
    switch (op) {
        case '+': return a + b;
        case '-': return a - b;
        case '*': return a * b;
        case '/': return a / b;
    }
};

})(require('../tree'));


(function (tree) {

tree.Paren = function (node) {
    this.value = node;
};
tree.Paren.prototype = {
    type: "Paren",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    genCSS: function (env, output) {
        output.add('(');
        this.value.genCSS(env, output);
        output.add(')');
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        return new(tree.Paren)(this.value.eval(env));
    }
};

})(require('../tree'));

(function (tree) {

tree.Quoted = function (str, content, escaped, index, currentFileInfo) {
    this.escaped = escaped;
    this.value = content || '';
    this.quote = str.charAt(0);
    this.index = index;
    this.currentFileInfo = currentFileInfo;
};
tree.Quoted.prototype = {
    type: "Quoted",
    genCSS: function (env, output) {
        if (!this.escaped) {
            output.add(this.quote, this.currentFileInfo, this.index);
        }
        output.add(this.value);
        if (!this.escaped) {
            output.add(this.quote);
        }
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        var that = this;
        var value = this.value.replace(/`([^`]+)`/g, function (_, exp) {
            return new(tree.JavaScript)(exp, that.index, true).eval(env).value;
        }).replace(/@\{([\w-]+)\}/g, function (_, name) {
            var v = new(tree.Variable)('@' + name, that.index, that.currentFileInfo).eval(env, true);
            return (v instanceof tree.Quoted) ? v.value : v.toCSS();
        });
        return new(tree.Quoted)(this.quote + value + this.quote, value, this.escaped, this.index, this.currentFileInfo);
    },
    compare: function (x) {
        if (!x.toCSS) {
            return -1;
        }
        
        var left = this.toCSS(),
            right = x.toCSS();
        
        if (left === right) {
            return 0;
        }
        
        return left < right ? -1 : 1;
    }
};

})(require('../tree'));

(function (tree) {

tree.Rule = function (name, value, important, merge, index, currentFileInfo, inline) {
    this.name = name;
    this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
    this.important = important ? ' ' + important.trim() : '';
    this.merge = merge;
    this.index = index;
    this.currentFileInfo = currentFileInfo;
    this.inline = inline || false;
    this.variable = name.charAt && (name.charAt(0) === '@');
};

tree.Rule.prototype = {
    type: "Rule",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    genCSS: function (env, output) {
        output.add(this.name + (env.compress ? ':' : ': '), this.currentFileInfo, this.index);
        try {
            this.value.genCSS(env, output);
        }
        catch(e) {
            e.index = this.index;
            e.filename = this.currentFileInfo.filename;
            throw e;
        }
        output.add(this.important + ((this.inline || (env.lastRule && env.compress)) ? "" : ";"), this.currentFileInfo, this.index);
    },
    toCSS: tree.toCSS,
    eval: function (env) {
        var strictMathBypass = false;
        var name = this.name.map ? 
            this.name.map( function(v) {
                return v.eval ? v.eval(env).value : v;
            }).join('') : this.name;
        if (name === "font" && !env.strictMath) {
            strictMathBypass = true;
            env.strictMath = true;
        }
        try {
            return new(tree.Rule)(name,
                              this.value.eval(env),
                              this.important,
                              this.merge,
                              this.index, this.currentFileInfo, this.inline);
        }
        catch(e) {
            if (e.index === undefined) {
                e.index = this.index;
            }
            throw e;
        }
        finally {
            if (strictMathBypass) {
                env.strictMath = false;
            }
        }
    },
    makeImportant: function () {
        return new(tree.Rule)(this.name,
                              this.value,
                              "!important",
                              this.merge,
                              this.index, this.currentFileInfo, this.inline);
    }
};

})(require('../tree'));

(function (tree) {

tree.Ruleset = function (selectors, rules, strictImports) {
    this.selectors = selectors;
    this.rules = rules;
    this._lookups = {};
    this.strictImports = strictImports;
};
tree.Ruleset.prototype = {
    type: "Ruleset",
    accept: function (visitor) {
        if (this.paths) {
            visitor.visitArray(this.paths, true);
        } else if (this.selectors) {
            this.selectors = visitor.visitArray(this.selectors);
        }
        if (this.rules && this.rules.length) {
            this.rules = visitor.visitArray(this.rules);
        }
    },
    eval: function (env) {
        var thisSelectors = this.selectors, selectors, 
            selCnt, i, defaultFunc = tree.defaultFunc;
        if (thisSelectors && (selCnt = thisSelectors.length)) {
            selectors = [];
            defaultFunc.error({
                type: "Syntax", 
                message: "it is currently only allowed in parametric mixin guards," 
            });
            for (i = 0; i < selCnt; i++) {
                selectors.push(thisSelectors[i].eval(env));
            }
            defaultFunc.reset();  
        }

        var rules = this.rules ? this.rules.slice(0) : null,
            ruleset = new(tree.Ruleset)(selectors, rules, this.strictImports),
            rule;

        ruleset.originalRuleset = this;
        ruleset.root = this.root;
        ruleset.firstRoot = this.firstRoot;
        ruleset.allowImports = this.allowImports;

        if(this.debugInfo) {
            ruleset.debugInfo = this.debugInfo;
        }

        // push the current ruleset to the frames stack
        var envFrames = env.frames;
        envFrames.unshift(ruleset);

        // currrent selectors
        var envSelectors = env.selectors;
        if (!envSelectors) {
            env.selectors = envSelectors = [];
        }
        envSelectors.unshift(this.selectors);

        // Evaluate imports
        if (ruleset.root || ruleset.allowImports || !ruleset.strictImports) {
            ruleset.evalImports(env);
        }

        // Store the frames around mixin definitions,
        // so they can be evaluated like closures when the time comes.
        var rsRules = ruleset.rules, rsRuleCnt = rsRules ? rsRules.length : 0;
        for (i = 0; i < rsRuleCnt; i++) {
            if (rsRules[i] instanceof tree.mixin.Definition) {
                rsRules[i].frames = envFrames.slice(0);
            }
        }

        var mediaBlockCount = (env.mediaBlocks && env.mediaBlocks.length) || 0;

        // Evaluate mixin calls.
        for (i = 0; i < rsRuleCnt; i++) {
            if (rsRules[i] instanceof tree.mixin.Call) {
                /*jshint loopfunc:true */
                rules = rsRules[i].eval(env).filter(function(r) {
                    if ((r instanceof tree.Rule) && r.variable) {
                        // do not pollute the scope if the variable is
                        // already there. consider returning false here
                        // but we need a way to "return" variable from mixins
                        return !(ruleset.variable(r.name));
                    }
                    return true;
                });
                rsRules.splice.apply(rsRules, [i, 1].concat(rules));
                rsRuleCnt += rules.length - 1;
                i += rules.length-1;
                ruleset.resetCache();
            }
        }

        // Evaluate everything else
        for (i = 0; i < rsRuleCnt; i++) {
            rule = rsRules[i];
            if (! (rule instanceof tree.mixin.Definition)) {
                rsRules[i] = rule.eval ? rule.eval(env) : rule;
            }
        }

        // Pop the stack
        envFrames.shift();
        envSelectors.shift();
        
        if (env.mediaBlocks) {
            for (i = mediaBlockCount; i < env.mediaBlocks.length; i++) {
                env.mediaBlocks[i].bubbleSelectors(selectors);
            }
        }

        return ruleset;
    },
    evalImports: function(env) {
        var rules = this.rules, i, importRules;
        if (!rules) { return; }

        for (i = 0; i < rules.length; i++) {
            if (rules[i] instanceof tree.Import) {
                importRules = rules[i].eval(env);
                if (importRules && importRules.length) {
                    rules.splice.apply(rules, [i, 1].concat(importRules));
                    i+= importRules.length-1;
                } else {
                    rules.splice(i, 1, importRules);
                }
                this.resetCache();
            }
        }
    },
    makeImportant: function() {
        return new tree.Ruleset(this.selectors, this.rules.map(function (r) {
                    if (r.makeImportant) {
                        return r.makeImportant();
                    } else {
                        return r;
                    }
                }), this.strictImports);
    },
    matchArgs: function (args) {
        return !args || args.length === 0;
    },
    matchCondition: function (args, env) {
        var lastSelector = this.selectors[this.selectors.length-1];
        if (lastSelector.condition &&
            !lastSelector.condition.eval(
                new(tree.evalEnv)(env,
                    env.frames))) {
            return false;
        }
        return true;
    },
    resetCache: function () {
        this._rulesets = null;
        this._variables = null;
        this._lookups = {};
    },
    variables: function () {
        if (!this._variables) {
            this._variables = !this.rules ? {} : this.rules.reduce(function (hash, r) {
                if (r instanceof tree.Rule && r.variable === true) {
                    hash[r.name] = r;
                }
                return hash;
            }, {});
        }
        return this._variables;
    },
    variable: function (name) {
        return this.variables()[name];
    },
    rulesets: function () {
        if (!this.rules) { return null; }

        var _Ruleset = tree.Ruleset, _MixinDefinition = tree.mixin.Definition,
            filtRules = [], rules = this.rules, cnt = rules.length,
            i, rule;

        for (i = 0; i < cnt; i++) {
            rule = rules[i];
            if ((rule instanceof _Ruleset) || (rule instanceof _MixinDefinition)) {
                filtRules.push(rule);
            }
        }

        return filtRules;
    },
    prependRule: function (rule) {
        var rules = this.rules;
        if (rules) { rules.unshift(rule); } else { this.rules = [ rule ]; }
    },
    find: function (selector, self) {
        self = self || this;
        var rules = [], match,
            key = selector.toCSS();

        if (key in this._lookups) { return this._lookups[key]; }

        this.rulesets().forEach(function (rule) {
            if (rule !== self) {
                for (var j = 0; j < rule.selectors.length; j++) {
                    match = selector.match(rule.selectors[j]);
                    if (match) {
                        if (selector.elements.length > match) {
                            Array.prototype.push.apply(rules, rule.find(
                                new(tree.Selector)(selector.elements.slice(match)), self));
                        } else {
                            rules.push(rule);
                        }
                        break;
                    }
                }
            }
        });
        this._lookups[key] = rules;
        return rules;
    },
    genCSS: function (env, output) {
        var i, j,
            ruleNodes = [],
            rulesetNodes = [],
            rulesetNodeCnt,
            debugInfo,     // Line number debugging
            rule,
            path;

        env.tabLevel = (env.tabLevel || 0);

        if (!this.root) {
            env.tabLevel++;
        }

        var tabRuleStr = env.compress ? '' : Array(env.tabLevel + 1).join("  "),
            tabSetStr = env.compress ? '' : Array(env.tabLevel).join("  "),
            sep;

        for (i = 0; i < this.rules.length; i++) {
            rule = this.rules[i];
            if (rule.rules || (rule instanceof tree.Media) || rule instanceof tree.Directive || (this.root && rule instanceof tree.Comment)) {
                rulesetNodes.push(rule);
            } else {
                ruleNodes.push(rule);
            }
        }

        // If this is the root node, we don't render
        // a selector, or {}.
        if (!this.root) {
            debugInfo = tree.debugInfo(env, this, tabSetStr);

            if (debugInfo) {
                output.add(debugInfo);
                output.add(tabSetStr);
            }

            var paths = this.paths, pathCnt = paths.length,
                pathSubCnt;

            sep = env.compress ? ',' : (',\n' + tabSetStr);

            for (i = 0; i < pathCnt; i++) {
                path = paths[i];
                if (!(pathSubCnt = path.length)) { continue; }
                if (i > 0) { output.add(sep); }

                env.firstSelector = true;
                path[0].genCSS(env, output);

                env.firstSelector = false;
                for (j = 1; j < pathSubCnt; j++) {
                    path[j].genCSS(env, output);
                }
            }

            output.add((env.compress ? '{' : ' {\n') + tabRuleStr);
        }

        // Compile rules and rulesets
        for (i = 0; i < ruleNodes.length; i++) {
            rule = ruleNodes[i];

            // @page{ directive ends up with root elements inside it, a mix of rules and rulesets
            // In this instance we do not know whether it is the last property
            if (i + 1 === ruleNodes.length && (!this.root || rulesetNodes.length === 0 || this.firstRoot)) {
                env.lastRule = true;
            }

            if (rule.genCSS) {
                rule.genCSS(env, output);
            } else if (rule.value) {
                output.add(rule.value.toString());
            }

            if (!env.lastRule) {
                output.add(env.compress ? '' : ('\n' + tabRuleStr));
            } else {
                env.lastRule = false;
            }
        }

        if (!this.root) {
            output.add((env.compress ? '}' : '\n' + tabSetStr + '}'));
            env.tabLevel--;
        }

        sep = (env.compress ? "" : "\n") + (this.root ? tabRuleStr : tabSetStr);
        rulesetNodeCnt = rulesetNodes.length;
        if (rulesetNodeCnt) {
            if (ruleNodes.length && sep) { output.add(sep); }
            rulesetNodes[0].genCSS(env, output);
            for (i = 1; i < rulesetNodeCnt; i++) {
                if (sep) { output.add(sep); }
                rulesetNodes[i].genCSS(env, output);
            }
        }

        if (!output.isEmpty() && !env.compress && this.firstRoot) {
            output.add('\n');
        }
    },

    toCSS: tree.toCSS,

    markReferenced: function () {
        for (var s = 0; s < this.selectors.length; s++) {
            this.selectors[s].markReferenced();
        }
    },

    joinSelectors: function (paths, context, selectors) {
        for (var s = 0; s < selectors.length; s++) {
            this.joinSelector(paths, context, selectors[s]);
        }
    },

    joinSelector: function (paths, context, selector) {

        var i, j, k, 
            hasParentSelector, newSelectors, el, sel, parentSel, 
            newSelectorPath, afterParentJoin, newJoinedSelector, 
            newJoinedSelectorEmpty, lastSelector, currentElements,
            selectorsMultiplied;
    
        for (i = 0; i < selector.elements.length; i++) {
            el = selector.elements[i];
            if (el.value === '&') {
                hasParentSelector = true;
            }
        }
    
        if (!hasParentSelector) {
            if (context.length > 0) {
                for (i = 0; i < context.length; i++) {
                    paths.push(context[i].concat(selector));
                }
            }
            else {
                paths.push([selector]);
            }
            return;
        }

        // The paths are [[Selector]]
        // The first list is a list of comma seperated selectors
        // The inner list is a list of inheritance seperated selectors
        // e.g.
        // .a, .b {
        //   .c {
        //   }
        // }
        // == [[.a] [.c]] [[.b] [.c]]
        //

        // the elements from the current selector so far
        currentElements = [];
        // the current list of new selectors to add to the path.
        // We will build it up. We initiate it with one empty selector as we "multiply" the new selectors
        // by the parents
        newSelectors = [[]];

        for (i = 0; i < selector.elements.length; i++) {
            el = selector.elements[i];
            // non parent reference elements just get added
            if (el.value !== "&") {
                currentElements.push(el);
            } else {
                // the new list of selectors to add
                selectorsMultiplied = [];

                // merge the current list of non parent selector elements
                // on to the current list of selectors to add
                if (currentElements.length > 0) {
                    this.mergeElementsOnToSelectors(currentElements, newSelectors);
                }

                // loop through our current selectors
                for (j = 0; j < newSelectors.length; j++) {
                    sel = newSelectors[j];
                    // if we don't have any parent paths, the & might be in a mixin so that it can be used
                    // whether there are parents or not
                    if (context.length === 0) {
                        // the combinator used on el should now be applied to the next element instead so that
                        // it is not lost
                        if (sel.length > 0) {
                            sel[0].elements = sel[0].elements.slice(0);
                            sel[0].elements.push(new(tree.Element)(el.combinator, '', 0, el.index, el.currentFileInfo));
                        }
                        selectorsMultiplied.push(sel);
                    }
                    else {
                        // and the parent selectors
                        for (k = 0; k < context.length; k++) {
                            parentSel = context[k];
                            // We need to put the current selectors
                            // then join the last selector's elements on to the parents selectors

                            // our new selector path
                            newSelectorPath = [];
                            // selectors from the parent after the join
                            afterParentJoin = [];
                            newJoinedSelectorEmpty = true;

                            //construct the joined selector - if & is the first thing this will be empty,
                            // if not newJoinedSelector will be the last set of elements in the selector
                            if (sel.length > 0) {
                                newSelectorPath = sel.slice(0);
                                lastSelector = newSelectorPath.pop();
                                newJoinedSelector = selector.createDerived(lastSelector.elements.slice(0));
                                newJoinedSelectorEmpty = false;
                            }
                            else {
                                newJoinedSelector = selector.createDerived([]);
                            }

                            //put together the parent selectors after the join
                            if (parentSel.length > 1) {
                                afterParentJoin = afterParentJoin.concat(parentSel.slice(1));
                            }

                            if (parentSel.length > 0) {
                                newJoinedSelectorEmpty = false;

                                // join the elements so far with the first part of the parent
                                newJoinedSelector.elements.push(new(tree.Element)(el.combinator, parentSel[0].elements[0].value, el.index, el.currentFileInfo));
                                newJoinedSelector.elements = newJoinedSelector.elements.concat(parentSel[0].elements.slice(1));
                            }

                            if (!newJoinedSelectorEmpty) {
                                // now add the joined selector
                                newSelectorPath.push(newJoinedSelector);
                            }

                            // and the rest of the parent
                            newSelectorPath = newSelectorPath.concat(afterParentJoin);

                            // add that to our new set of selectors
                            selectorsMultiplied.push(newSelectorPath);
                        }
                    }
                }

                // our new selectors has been multiplied, so reset the state
                newSelectors = selectorsMultiplied;
                currentElements = [];
            }
        }

        // if we have any elements left over (e.g. .a& .b == .b)
        // add them on to all the current selectors
        if (currentElements.length > 0) {
            this.mergeElementsOnToSelectors(currentElements, newSelectors);
        }

        for (i = 0; i < newSelectors.length; i++) {
            if (newSelectors[i].length > 0) {
                paths.push(newSelectors[i]);
            }
        }
    },
    
    mergeElementsOnToSelectors: function(elements, selectors) {
        var i, sel;

        if (selectors.length === 0) {
            selectors.push([ new(tree.Selector)(elements) ]);
            return;
        }

        for (i = 0; i < selectors.length; i++) {
            sel = selectors[i];

            // if the previous thing in sel is a parent this needs to join on to it
            if (sel.length > 0) {
                sel[sel.length - 1] = sel[sel.length - 1].createDerived(sel[sel.length - 1].elements.concat(elements));
            }
            else {
                sel.push(new(tree.Selector)(elements));
            }
        }
    }
};
})(require('../tree'));

(function (tree) {

tree.Selector = function (elements, extendList, condition, index, currentFileInfo, isReferenced) {
    this.elements = elements;
    this.extendList = extendList;
    this.condition = condition;
    this.currentFileInfo = currentFileInfo || {};
    this.isReferenced = isReferenced;
    if (!condition) {
        this.evaldCondition = true;
    }
};
tree.Selector.prototype = {
    type: "Selector",
    accept: function (visitor) {
        if (this.elements) {
            this.elements = visitor.visitArray(this.elements);
        }
        if (this.extendList) {
            this.extendList = visitor.visitArray(this.extendList);
        }
        if (this.condition) {
            this.condition = visitor.visit(this.condition);
        }
    },
    createDerived: function(elements, extendList, evaldCondition) {
        evaldCondition = (evaldCondition != null) ? evaldCondition : this.evaldCondition;
        var newSelector = new(tree.Selector)(elements, extendList || this.extendList, this.condition, this.index, this.currentFileInfo, this.isReferenced);
        newSelector.evaldCondition = evaldCondition;
        return newSelector;
    },
    match: function (other) {
        var elements = this.elements,
            len = elements.length,
            oelements, olen, i;
            
        oelements = other.elements.map( function(v) {
            return v.combinator.value + (v.value.value || v.value);
        }).join("").match(/[,&#\.\w-]([\w-]|(\\.))*/g); 
        // ^ regexp could be more simple but see test/less/css-escapes.less:17, doh!
        
        if (!oelements) {
            return 0;
        }

        if (oelements[0] === "&") {
            oelements.shift();
        }

        olen = oelements.length;
        if (olen === 0 || len < olen) {
            return 0;
        } else {
            for (i = 0; i < olen; i++) {
                if (elements[i].value !== oelements[i]) {
                    return 0;
                }
            }
        }
        return olen; // return number of matched elements
    },
    eval: function (env) {
        var evaldCondition = this.condition && this.condition.eval(env),
            elements = this.elements, extendList = this.extendList;

        elements = elements && elements.map(function (e) { return e.eval(env); });
        extendList = extendList && extendList.map(function(extend) { return extend.eval(env); });

        return this.createDerived(elements, extendList, evaldCondition);
    },
    genCSS: function (env, output) {
        var i, element;
        if ((!env || !env.firstSelector) && this.elements[0].combinator.value === "") {
            output.add(' ', this.currentFileInfo, this.index);
        }
        if (!this._css) {
            //TODO caching? speed comparison?
            for(i = 0; i < this.elements.length; i++) {
                element = this.elements[i];
                element.genCSS(env, output);
            }
        }
    },
    toCSS: tree.toCSS,
    markReferenced: function () {
        this.isReferenced = true;
    },
    getIsReferenced: function() {
        return !this.currentFileInfo.reference || this.isReferenced;
    },
    getIsOutput: function() {
        return this.evaldCondition;
    }
};

})(require('../tree'));

(function (tree) {

tree.UnicodeDescriptor = function (value) {
    this.value = value;
};
tree.UnicodeDescriptor.prototype = {
    type: "UnicodeDescriptor",
    genCSS: function (env, output) {
        output.add(this.value);
    },
    toCSS: tree.toCSS,
    eval: function () { return this; }
};

})(require('../tree'));

(function (tree) {

tree.URL = function (val, currentFileInfo, isEvald) {
    this.value = val;
    this.currentFileInfo = currentFileInfo;
    this.isEvald = isEvald;
};
tree.URL.prototype = {
    type: "Url",
    accept: function (visitor) {
        this.value = visitor.visit(this.value);
    },
    genCSS: function (env, output) {
        output.add("url(");
        this.value.genCSS(env, output);
        output.add(")");
    },
    toCSS: tree.toCSS,
    eval: function (ctx) {
        var val = this.value.eval(ctx),
            rootpath;

        if (!this.isEvald) {
            // Add the base path if the URL is relative
            rootpath = this.currentFileInfo && this.currentFileInfo.rootpath;
            if (rootpath && typeof val.value === "string" && ctx.isPathRelative(val.value)) {
                if (!val.quote) {
                    rootpath = rootpath.replace(/[\(\)'"\s]/g, function(match) { return "\\"+match; });
                }
                val.value = rootpath + val.value;
            }
            
            val.value = ctx.normalizePath(val.value);
        }

        return new(tree.URL)(val, this.currentFileInfo, true);
    }
};

})(require('../tree'));

(function (tree) {

tree.Value = function (value) {
    this.value = value;
};
tree.Value.prototype = {
    type: "Value",
    accept: function (visitor) {
        if (this.value) {
            this.value = visitor.visitArray(this.value);
        }
    },
    eval: function (env) {
        if (this.value.length === 1) {
            return this.value[0].eval(env);
        } else {
            return new(tree.Value)(this.value.map(function (v) {
                return v.eval(env);
            }));
        }
    },
    genCSS: function (env, output) {
        var i;
        for(i = 0; i < this.value.length; i++) {
            this.value[i].genCSS(env, output);
            if (i+1 < this.value.length) {
                output.add((env && env.compress) ? ',' : ', ');
            }
        }
    },
    toCSS: tree.toCSS
};

})(require('../tree'));

(function (tree) {

tree.Variable = function (name, index, currentFileInfo) {
    this.name = name;
    this.index = index;
    this.currentFileInfo = currentFileInfo || {};
};
tree.Variable.prototype = {
    type: "Variable",
    eval: function (env) {
        var variable, name = this.name;

        if (name.indexOf('@@') === 0) {
            name = '@' + new(tree.Variable)(name.slice(1)).eval(env).value;
        }
        
        if (this.evaluating) {
            throw { type: 'Name',
                    message: "Recursive variable definition for " + name,
                    filename: this.currentFileInfo.file,
                    index: this.index };
        }
        
        this.evaluating = true;

        variable = tree.find(env.frames, function (frame) {
            var v = frame.variable(name);
            if (v) {
                return v.value.eval(env);
            }
        });
        if (variable) { 
            this.evaluating = false;
            return variable;
        } else {
            throw { type: 'Name',
                    message: "variable " + name + " is undefined",
                    filename: this.currentFileInfo.filename,
                    index: this.index };
        }
    }
};

})(require('../tree'));

(function (tree) {

    var parseCopyProperties = [
        'paths',            // option - unmodified - paths to search for imports on
        'optimization',     // option - optimization level (for the chunker)
        'files',            // list of files that have been imported, used for import-once
        'contents',         // map - filename to contents of all the files
        'contentsIgnoredChars', // map - filename to lines at the begining of each file to ignore
        'relativeUrls',     // option - whether to adjust URL's to be relative
        'rootpath',         // option - rootpath to append to URL's
        'strictImports',    // option -
        'insecure',         // option - whether to allow imports from insecure ssl hosts
        'dumpLineNumbers',  // option - whether to dump line numbers
        'compress',         // option - whether to compress
        'processImports',   // option - whether to process imports. if false then imports will not be imported
        'syncImport',       // option - whether to import synchronously
        'javascriptEnabled',// option - whether JavaScript is enabled. if undefined, defaults to true
        'mime',             // browser only - mime type for sheet import
        'useFileCache',     // browser only - whether to use the per file session cache
        'currentFileInfo'   // information about the current file - for error reporting and importing and making urls relative etc.
    ];

    //currentFileInfo = {
    //  'relativeUrls' - option - whether to adjust URL's to be relative
    //  'filename' - full resolved filename of current file
    //  'rootpath' - path to append to normal URLs for this node
    //  'currentDirectory' - path to the current file, absolute
    //  'rootFilename' - filename of the base file
    //  'entryPath' - absolute path to the entry file
    //  'reference' - whether the file should not be output and only output parts that are referenced

    tree.parseEnv = function(options) {
        copyFromOriginal(options, this, parseCopyProperties);

        if (!this.contents) { this.contents = {}; }
        if (!this.contentsIgnoredChars) { this.contentsIgnoredChars = {}; }
        if (!this.files) { this.files = {}; }

        if (!this.currentFileInfo) {
            var filename = (options && options.filename) || "input";
            var entryPath = filename.replace(/[^\/\\]*$/, "");
            if (options) {
                options.filename = null;
            }
            this.currentFileInfo = {
                filename: filename,
                relativeUrls: this.relativeUrls,
                rootpath: (options && options.rootpath) || "",
                currentDirectory: entryPath,
                entryPath: entryPath,
                rootFilename: filename
            };
        }
    };

    var evalCopyProperties = [
        'silent',      // whether to swallow errors and warnings
        'verbose',     // whether to log more activity
        'compress',    // whether to compress
        'yuicompress', // whether to compress with the outside tool yui compressor
        'ieCompat',    // whether to enforce IE compatibility (IE8 data-uri)
        'strictMath',  // whether math has to be within parenthesis
        'strictUnits', // whether units need to evaluate correctly
        'cleancss',    // whether to compress with clean-css
        'sourceMap',   // whether to output a source map
        'importMultiple'// whether we are currently importing multiple copies
        ];

    tree.evalEnv = function(options, frames) {
        copyFromOriginal(options, this, evalCopyProperties);

        this.frames = frames || [];
    };

    tree.evalEnv.prototype.inParenthesis = function () {
        if (!this.parensStack) {
            this.parensStack = [];
        }
        this.parensStack.push(true);
    };

    tree.evalEnv.prototype.outOfParenthesis = function () {
        this.parensStack.pop();
    };

    tree.evalEnv.prototype.isMathOn = function () {
        return this.strictMath ? (this.parensStack && this.parensStack.length) : true;
    };

    tree.evalEnv.prototype.isPathRelative = function (path) {
        return !/^(?:[a-z-]+:|\/)/.test(path);
    };

    tree.evalEnv.prototype.normalizePath = function( path ) {
        var
          segments = path.split("/").reverse(),
          segment;

        path = [];
        while (segments.length !== 0 ) {
            segment = segments.pop();
            switch( segment ) {
                case ".":
                    break;
                case "..":
                    if ((path.length === 0) || (path[path.length - 1] === "..")) {
                        path.push( segment );
                    } else {
                        path.pop();
                    }
                    break;
                default:
                    path.push( segment );
                    break;
            }
        }

        return path.join("/");
    };

    //todo - do the same for the toCSS env
    //tree.toCSSEnv = function (options) {
    //};

    var copyFromOriginal = function(original, destination, propertiesToCopy) {
        if (!original) { return; }

        for(var i = 0; i < propertiesToCopy.length; i++) {
            if (original.hasOwnProperty(propertiesToCopy[i])) {
                destination[propertiesToCopy[i]] = original[propertiesToCopy[i]];
            }
        }
    };

})(require('./tree'));

(function (tree) {

    var _visitArgs = { visitDeeper: true },
        _hasIndexed = false;

    function _noop(node) {
        return node;
    }

    function indexNodeTypes(parent, ticker) {
        // add .typeIndex to tree node types for lookup table
        var key, child;
        for (key in parent) {
            if (parent.hasOwnProperty(key)) {
                child = parent[key];
                switch (typeof child) {
                    case "function":
                        // ignore bound functions directly on tree which do not have a prototype
                        // or aren't nodes
                        if (child.prototype && child.prototype.type) {
                            child.prototype.typeIndex = ticker++;
                        }
                        break;
                    case "object":
                        ticker = indexNodeTypes(child, ticker);
                        break;
                }
            }
        }
        return ticker;
    }

    tree.visitor = function(implementation) {
        this._implementation = implementation;
        this._visitFnCache = [];

        if (!_hasIndexed) {
            indexNodeTypes(tree, 1);
            _hasIndexed = true;
        }
    };

    tree.visitor.prototype = {
        visit: function(node) {
            if (!node) {
                return node;
            }

            var nodeTypeIndex = node.typeIndex;
            if (!nodeTypeIndex) {
                return node;
            }

            var visitFnCache = this._visitFnCache,
                impl = this._implementation,
                aryIndx = nodeTypeIndex << 1,
                outAryIndex = aryIndx | 1,
                func = visitFnCache[aryIndx],
                funcOut = visitFnCache[outAryIndex],
                visitArgs = _visitArgs,
                fnName;

            visitArgs.visitDeeper = true;

            if (!func) {
                fnName = "visit" + node.type;
                func = impl[fnName] || _noop;
                funcOut = impl[fnName + "Out"] || _noop;
                visitFnCache[aryIndx] = func;
                visitFnCache[outAryIndex] = funcOut;
            }

            if (func !== _noop) {
                var newNode = func.call(impl, node, visitArgs);
                if (impl.isReplacing) {
                    node = newNode;
                }
            }

            if (visitArgs.visitDeeper && node && node.accept) {
                node.accept(this);
            }

            if (funcOut != _noop) {
                funcOut.call(impl, node);
            }

            return node;
        },
        visitArray: function(nodes, nonReplacing) {
            if (!nodes) {
                return nodes;
            }

            var cnt = nodes.length, i;

            // Non-replacing
            if (nonReplacing || !this._implementation.isReplacing) {
                for (i = 0; i < cnt; i++) {
                    this.visit(nodes[i]);
                }
                return nodes;
            }

            // Replacing
            var out = [];
            for (i = 0; i < cnt; i++) {
                var evald = this.visit(nodes[i]);
                if (!evald.splice) {
                    out.push(evald);
                } else if (evald.length) {
                    this.flatten(evald, out);
                }
            }
            return out;
        },
        flatten: function(arr, out) {
            if (!out) {
                out = [];
            }

            var cnt, i, item,
                nestedCnt, j, nestedItem;

            for (i = 0, cnt = arr.length; i < cnt; i++) {
                item = arr[i];
                if (!item.splice) {
                    out.push(item);
                    continue;
                }

                for (j = 0, nestedCnt = item.length; j < nestedCnt; j++) {
                    nestedItem = item[j];
                    if (!nestedItem.splice) {
                        out.push(nestedItem);
                    } else if (nestedItem.length) {
                        this.flatten(nestedItem, out);
                    }
                }
            }

            return out;
        }
    };

})(require('./tree'));
(function (tree) {
    tree.importVisitor = function(importer, finish, evalEnv) {
        this._visitor = new tree.visitor(this);
        this._importer = importer;
        this._finish = finish;
        this.env = evalEnv || new tree.evalEnv();
        this.importCount = 0;
    };

    tree.importVisitor.prototype = {
        isReplacing: true,
        run: function (root) {
            var error;
            try {
                // process the contents
                this._visitor.visit(root);
            }
            catch(e) {
                error = e;
            }

            this.isFinished = true;

            if (this.importCount === 0) {
                this._finish(error);
            }
        },
        visitImport: function (importNode, visitArgs) {
            var importVisitor = this,
                evaldImportNode,
                inlineCSS = importNode.options.inline;

            if (!importNode.css || inlineCSS) {

                try {
                    evaldImportNode = importNode.evalForImport(this.env);
                } catch(e){
                    if (!e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }
                    // attempt to eval properly and treat as css
                    importNode.css = true;
                    // if that fails, this error will be thrown
                    importNode.error = e;
                }

                if (evaldImportNode && (!evaldImportNode.css || inlineCSS)) {
                    importNode = evaldImportNode;
                    this.importCount++;
                    var env = new tree.evalEnv(this.env, this.env.frames.slice(0));

                    if (importNode.options.multiple) {
                        env.importMultiple = true;
                    }

                    this._importer.push(importNode.getPath(), importNode.currentFileInfo, importNode.options, function (e, root, imported, fullPath) {
                        if (e && !e.filename) { e.index = importNode.index; e.filename = importNode.currentFileInfo.filename; }

                        if (imported && !env.importMultiple) { importNode.skip = imported; }

                        var subFinish = function(e) {
                            importVisitor.importCount--;

                            if (importVisitor.importCount === 0 && importVisitor.isFinished) {
                                importVisitor._finish(e);
                            }
                        };

                        if (root) {
                            importNode.root = root;
                            importNode.importedFilename = fullPath;
                            if (!inlineCSS && !importNode.skip) {
                                new(tree.importVisitor)(importVisitor._importer, subFinish, env)
                                    .run(root);
                                return;
                            }
                        }

                        subFinish();
                    });
                }
            }
            visitArgs.visitDeeper = false;
            return importNode;
        },
        visitRule: function (ruleNode, visitArgs) {
            visitArgs.visitDeeper = false;
            return ruleNode;
        },
        visitDirective: function (directiveNode, visitArgs) {
            this.env.frames.unshift(directiveNode);
            return directiveNode;
        },
        visitDirectiveOut: function (directiveNode) {
            this.env.frames.shift();
        },
        visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
            this.env.frames.unshift(mixinDefinitionNode);
            return mixinDefinitionNode;
        },
        visitMixinDefinitionOut: function (mixinDefinitionNode) {
            this.env.frames.shift();
        },
        visitRuleset: function (rulesetNode, visitArgs) {
            this.env.frames.unshift(rulesetNode);
            return rulesetNode;
        },
        visitRulesetOut: function (rulesetNode) {
            this.env.frames.shift();
        },
        visitMedia: function (mediaNode, visitArgs) {
            this.env.frames.unshift(mediaNode.ruleset);
            return mediaNode;
        },
        visitMediaOut: function (mediaNode) {
            this.env.frames.shift();
        }
    };

})(require('./tree'));
(function (tree) {
    tree.joinSelectorVisitor = function() {
        this.contexts = [[]];
        this._visitor = new tree.visitor(this);
    };

    tree.joinSelectorVisitor.prototype = {
        run: function (root) {
            return this._visitor.visit(root);
        },
        visitRule: function (ruleNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },

        visitRuleset: function (rulesetNode, visitArgs) {
            var context = this.contexts[this.contexts.length - 1],
                paths = [], selectors;

            this.contexts.push(paths);

            if (! rulesetNode.root) {
                selectors = rulesetNode.selectors;
                if (selectors) {
                    selectors = selectors.filter(function(selector) { return selector.getIsOutput(); });
                    rulesetNode.selectors = selectors.length ? selectors : (selectors = null);
                    if (selectors) { rulesetNode.joinSelectors(paths, context, selectors); }
                }
                if (!selectors) { rulesetNode.rules = null; }
                rulesetNode.paths = paths;
            }
        },
        visitRulesetOut: function (rulesetNode) {
            this.contexts.length = this.contexts.length - 1;
        },
        visitMedia: function (mediaNode, visitArgs) {
            var context = this.contexts[this.contexts.length - 1];
            mediaNode.rules[0].root = (context.length === 0 || context[0].multiMedia);
        }
    };

})(require('./tree'));
(function (tree) {
    tree.toCSSVisitor = function(env) {
        this._visitor = new tree.visitor(this);
        this._env = env;
    };

    tree.toCSSVisitor.prototype = {
        isReplacing: true,
        run: function (root) {
            return this._visitor.visit(root);
        },

        visitRule: function (ruleNode, visitArgs) {
            if (ruleNode.variable) {
                return [];
            }
            return ruleNode;
        },

        visitMixinDefinition: function (mixinNode, visitArgs) {
            return [];
        },

        visitExtend: function (extendNode, visitArgs) {
            return [];
        },

        visitComment: function (commentNode, visitArgs) {
            if (commentNode.isSilent(this._env)) {
                return [];
            }
            return commentNode;
        },

        visitMedia: function(mediaNode, visitArgs) {
            mediaNode.accept(this._visitor);
            visitArgs.visitDeeper = false;

            if (!mediaNode.rules.length) {
                return [];
            }
            return mediaNode;
        },

        visitDirective: function(directiveNode, visitArgs) {
            if (directiveNode.currentFileInfo.reference && !directiveNode.isReferenced) {
                return [];
            }
            if (directiveNode.name === "@charset") {
                // Only output the debug info together with subsequent @charset definitions
                // a comment (or @media statement) before the actual @charset directive would
                // be considered illegal css as it has to be on the first line
                if (this.charset) {
                    if (directiveNode.debugInfo) {
                        var comment = new tree.Comment("/* " + directiveNode.toCSS(this._env).replace(/\n/g, "")+" */\n");
                        comment.debugInfo = directiveNode.debugInfo;
                        return this._visitor.visit(comment);
                    }
                    return [];
                }
                this.charset = true;
            }
            return directiveNode;
        },

        checkPropertiesInRoot: function(rules) {
            var ruleNode;
            for(var i = 0; i < rules.length; i++) {
                ruleNode = rules[i];
                if (ruleNode instanceof tree.Rule && !ruleNode.variable) {
                    throw { message: "properties must be inside selector blocks, they cannot be in the root.",
                        index: ruleNode.index, filename: ruleNode.currentFileInfo ? ruleNode.currentFileInfo.filename : null};
                }
            }
        },

        visitRuleset: function (rulesetNode, visitArgs) {
            var rule, rulesets = [];
            if (rulesetNode.firstRoot) {
                this.checkPropertiesInRoot(rulesetNode.rules);
            }
            if (! rulesetNode.root) {
                if (rulesetNode.paths) {
                    rulesetNode.paths = rulesetNode.paths
                        .filter(function(p) {
                            var i;
                            if (p[0].elements[0].combinator.value === ' ') {
                                p[0].elements[0].combinator = new(tree.Combinator)('');
                            }
                            for(i = 0; i < p.length; i++) {
                                if (p[i].getIsReferenced() && p[i].getIsOutput()) {
                                    return true;
                                }
                            }
                            return false;
                        });
                }

                // Compile rules and rulesets
                var nodeRules = rulesetNode.rules, nodeRuleCnt = nodeRules ? nodeRules.length : 0;
                for (var i = 0; i < nodeRuleCnt; ) {
                    rule = nodeRules[i];
                    if (rule && rule.rules) {
                        // visit because we are moving them out from being a child
                        rulesets.push(this._visitor.visit(rule));
                        nodeRules.splice(i, 1);
                        nodeRuleCnt--;
                        continue;
                    }
                    i++;
                }
                // accept the visitor to remove rules and refactor itself
                // then we can decide now whether we want it or not
                if (nodeRuleCnt > 0) {
                    rulesetNode.accept(this._visitor);
                } else {
                    rulesetNode.rules = null;
                }
                visitArgs.visitDeeper = false;

                nodeRules = rulesetNode.rules;
                if (nodeRules) {
                    this._mergeRules(nodeRules);
                    nodeRules = rulesetNode.rules;
                }
                if (nodeRules) {
                    this._removeDuplicateRules(nodeRules);
                    nodeRules = rulesetNode.rules;
                }

                // now decide whether we keep the ruleset
                if (nodeRules && nodeRules.length > 0 && rulesetNode.paths.length > 0) {
                    rulesets.splice(0, 0, rulesetNode);
                }
            } else {
                rulesetNode.accept(this._visitor);
                visitArgs.visitDeeper = false;
                if (rulesetNode.firstRoot || (rulesetNode.rules && rulesetNode.rules.length > 0)) {
                    rulesets.splice(0, 0, rulesetNode);
                }
            }
            if (rulesets.length === 1) {
                return rulesets[0];
            }
            return rulesets;
        },

        _removeDuplicateRules: function(rules) {
            if (!rules) { return; }

            // remove duplicates
            var ruleCache = {},
                ruleList, rule, i;

            for(i = rules.length - 1; i >= 0 ; i--) {
                rule = rules[i];
                if (rule instanceof tree.Rule) {
                    if (!ruleCache[rule.name]) {
                        ruleCache[rule.name] = rule;
                    } else {
                        ruleList = ruleCache[rule.name];
                        if (ruleList instanceof tree.Rule) {
                            ruleList = ruleCache[rule.name] = [ruleCache[rule.name].toCSS(this._env)];
                        }
                        var ruleCSS = rule.toCSS(this._env);
                        if (ruleList.indexOf(ruleCSS) !== -1) {
                            rules.splice(i, 1);
                        } else {
                            ruleList.push(ruleCSS);
                        }
                    }
                }
            }
        },

        _mergeRules: function (rules) {
            if (!rules) { return; }

            var groups = {},
                parts,
                rule,
                key;

            for (var i = 0; i < rules.length; i++) {
                rule = rules[i];

                if ((rule instanceof tree.Rule) && rule.merge) {
                    key = [rule.name,
                        rule.important ? "!" : ""].join(",");

                    if (!groups[key]) {
                        groups[key] = [];
                    } else {
                        rules.splice(i--, 1);
                    }

                    groups[key].push(rule);
                }
            }

            Object.keys(groups).map(function (k) {
                parts = groups[k];

                if (parts.length > 1) {
                    rule = parts[0];

                    rule.value = new (tree.Value)(parts.map(function (p) {
                        return p.value;
                    }));
                }
            });
        }
    };

})(require('./tree'));
(function (tree) {
    /*jshint loopfunc:true */

    tree.extendFinderVisitor = function() {
        this._visitor = new tree.visitor(this);
        this.contexts = [];
        this.allExtendsStack = [[]];
    };

    tree.extendFinderVisitor.prototype = {
        run: function (root) {
            root = this._visitor.visit(root);
            root.allExtends = this.allExtendsStack[0];
            return root;
        },
        visitRule: function (ruleNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitRuleset: function (rulesetNode, visitArgs) {
            if (rulesetNode.root) {
                return;
            }

            var i, j, extend, allSelectorsExtendList = [], extendList;

            // get &:extend(.a); rules which apply to all selectors in this ruleset
            var rules = rulesetNode.rules, ruleCnt = rules ? rules.length : 0;
            for(i = 0; i < ruleCnt; i++) {
                if (rulesetNode.rules[i] instanceof tree.Extend) {
                    allSelectorsExtendList.push(rules[i]);
                    rulesetNode.extendOnEveryPath = true;
                }
            }

            // now find every selector and apply the extends that apply to all extends
            // and the ones which apply to an individual extend
            var paths = rulesetNode.paths;
            for(i = 0; i < paths.length; i++) {
                var selectorPath = paths[i],
                    selector = selectorPath[selectorPath.length - 1],
                    selExtendList = selector.extendList;

                extendList = selExtendList ? selExtendList.slice(0).concat(allSelectorsExtendList)
                                           : allSelectorsExtendList;

                if (extendList) {
                    extendList = extendList.map(function(allSelectorsExtend) {
                        return allSelectorsExtend.clone();
                    });
                }

                for(j = 0; j < extendList.length; j++) {
                    this.foundExtends = true;
                    extend = extendList[j];
                    extend.findSelfSelectors(selectorPath);
                    extend.ruleset = rulesetNode;
                    if (j === 0) { extend.firstExtendOnThisSelectorPath = true; }
                    this.allExtendsStack[this.allExtendsStack.length-1].push(extend);
                }
            }

            this.contexts.push(rulesetNode.selectors);
        },
        visitRulesetOut: function (rulesetNode) {
            if (!rulesetNode.root) {
                this.contexts.length = this.contexts.length - 1;
            }
        },
        visitMedia: function (mediaNode, visitArgs) {
            mediaNode.allExtends = [];
            this.allExtendsStack.push(mediaNode.allExtends);
        },
        visitMediaOut: function (mediaNode) {
            this.allExtendsStack.length = this.allExtendsStack.length - 1;
        },
        visitDirective: function (directiveNode, visitArgs) {
            directiveNode.allExtends = [];
            this.allExtendsStack.push(directiveNode.allExtends);
        },
        visitDirectiveOut: function (directiveNode) {
            this.allExtendsStack.length = this.allExtendsStack.length - 1;
        }
    };

    tree.processExtendsVisitor = function() {
        this._visitor = new tree.visitor(this);
    };

    tree.processExtendsVisitor.prototype = {
        run: function(root) {
            var extendFinder = new tree.extendFinderVisitor();
            extendFinder.run(root);
            if (!extendFinder.foundExtends) { return root; }
            root.allExtends = root.allExtends.concat(this.doExtendChaining(root.allExtends, root.allExtends));
            this.allExtendsStack = [root.allExtends];
            return this._visitor.visit(root);
        },
        doExtendChaining: function (extendsList, extendsListTarget, iterationCount) {
            //
            // chaining is different from normal extension.. if we extend an extend then we are not just copying, altering and pasting
            // the selector we would do normally, but we are also adding an extend with the same target selector
            // this means this new extend can then go and alter other extends
            //
            // this method deals with all the chaining work - without it, extend is flat and doesn't work on other extend selectors
            // this is also the most expensive.. and a match on one selector can cause an extension of a selector we had already processed if
            // we look at each selector at a time, as is done in visitRuleset

            var extendIndex, targetExtendIndex, matches, extendsToAdd = [], newSelector, extendVisitor = this, selectorPath, extend, targetExtend, newExtend;

            iterationCount = iterationCount || 0;

            //loop through comparing every extend with every target extend.
            // a target extend is the one on the ruleset we are looking at copy/edit/pasting in place
            // e.g.  .a:extend(.b) {}  and .b:extend(.c) {} then the first extend extends the second one
            // and the second is the target.
            // the seperation into two lists allows us to process a subset of chains with a bigger set, as is the
            // case when processing media queries
            for(extendIndex = 0; extendIndex < extendsList.length; extendIndex++){
                for(targetExtendIndex = 0; targetExtendIndex < extendsListTarget.length; targetExtendIndex++){

                    extend = extendsList[extendIndex];
                    targetExtend = extendsListTarget[targetExtendIndex];

                    // look for circular references
                    if( extend.parent_ids.indexOf( targetExtend.object_id ) >= 0 ){ continue; }

                    // find a match in the target extends self selector (the bit before :extend)
                    selectorPath = [targetExtend.selfSelectors[0]];
                    matches = extendVisitor.findMatch(extend, selectorPath);

                    if (matches.length) {

                        // we found a match, so for each self selector..
                        extend.selfSelectors.forEach(function(selfSelector) {

                            // process the extend as usual
                            newSelector = extendVisitor.extendSelector(matches, selectorPath, selfSelector);

                            // but now we create a new extend from it
                            newExtend = new(tree.Extend)(targetExtend.selector, targetExtend.option, 0);
                            newExtend.selfSelectors = newSelector;

                            // add the extend onto the list of extends for that selector
                            newSelector[newSelector.length-1].extendList = [newExtend];

                            // record that we need to add it.
                            extendsToAdd.push(newExtend);
                            newExtend.ruleset = targetExtend.ruleset;

                            //remember its parents for circular references
                            newExtend.parent_ids = newExtend.parent_ids.concat(targetExtend.parent_ids, extend.parent_ids);

                            // only process the selector once.. if we have :extend(.a,.b) then multiple
                            // extends will look at the same selector path, so when extending
                            // we know that any others will be duplicates in terms of what is added to the css
                            if (targetExtend.firstExtendOnThisSelectorPath) {
                                newExtend.firstExtendOnThisSelectorPath = true;
                                targetExtend.ruleset.paths.push(newSelector);
                            }
                        });
                    }
                }
            }

            if (extendsToAdd.length) {
                // try to detect circular references to stop a stack overflow.
                // may no longer be needed.
                this.extendChainCount++;
                if (iterationCount > 100) {
                    var selectorOne = "{unable to calculate}";
                    var selectorTwo = "{unable to calculate}";
                    try
                    {
                        selectorOne = extendsToAdd[0].selfSelectors[0].toCSS();
                        selectorTwo = extendsToAdd[0].selector.toCSS();
                    }
                    catch(e) {}
                    throw {message: "extend circular reference detected. One of the circular extends is currently:"+selectorOne+":extend(" + selectorTwo+")"};
                }

                // now process the new extends on the existing rules so that we can handle a extending b extending c ectending d extending e...
                return extendsToAdd.concat(extendVisitor.doExtendChaining(extendsToAdd, extendsListTarget, iterationCount+1));
            } else {
                return extendsToAdd;
            }
        },
        visitRule: function (ruleNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitSelector: function (selectorNode, visitArgs) {
            visitArgs.visitDeeper = false;
        },
        visitRuleset: function (rulesetNode, visitArgs) {
            if (rulesetNode.root) {
                return;
            }
            var matches, pathIndex, extendIndex, allExtends = this.allExtendsStack[this.allExtendsStack.length-1], selectorsToAdd = [], extendVisitor = this, selectorPath;

            // look at each selector path in the ruleset, find any extend matches and then copy, find and replace

            for(extendIndex = 0; extendIndex < allExtends.length; extendIndex++) {
                for(pathIndex = 0; pathIndex < rulesetNode.paths.length; pathIndex++) {
                    selectorPath = rulesetNode.paths[pathIndex];

                    // extending extends happens initially, before the main pass
                    if (rulesetNode.extendOnEveryPath) { continue; }
                    var extendList = selectorPath[selectorPath.length-1].extendList;
                    if (extendList && extendList.length) { continue; }

                    matches = this.findMatch(allExtends[extendIndex], selectorPath);

                    if (matches.length) {

                        allExtends[extendIndex].selfSelectors.forEach(function(selfSelector) {
                            selectorsToAdd.push(extendVisitor.extendSelector(matches, selectorPath, selfSelector));
                        });
                    }
                }
            }
            rulesetNode.paths = rulesetNode.paths.concat(selectorsToAdd);
        },
        findMatch: function (extend, haystackSelectorPath) {
            //
            // look through the haystack selector path to try and find the needle - extend.selector
            // returns an array of selector matches that can then be replaced
            //
            var haystackSelectorIndex, hackstackSelector, hackstackElementIndex, haystackElement,
                targetCombinator, i,
                extendVisitor = this,
                needleElements = extend.selector.elements,
                potentialMatches = [], potentialMatch, matches = [];

            // loop through the haystack elements
            for(haystackSelectorIndex = 0; haystackSelectorIndex < haystackSelectorPath.length; haystackSelectorIndex++) {
                hackstackSelector = haystackSelectorPath[haystackSelectorIndex];

                for(hackstackElementIndex = 0; hackstackElementIndex < hackstackSelector.elements.length; hackstackElementIndex++) {

                    haystackElement = hackstackSelector.elements[hackstackElementIndex];

                    // if we allow elements before our match we can add a potential match every time. otherwise only at the first element.
                    if (extend.allowBefore || (haystackSelectorIndex === 0 && hackstackElementIndex === 0)) {
                        potentialMatches.push({pathIndex: haystackSelectorIndex, index: hackstackElementIndex, matched: 0, initialCombinator: haystackElement.combinator});
                    }

                    for(i = 0; i < potentialMatches.length; i++) {
                        potentialMatch = potentialMatches[i];

                        // selectors add " " onto the first element. When we use & it joins the selectors together, but if we don't
                        // then each selector in haystackSelectorPath has a space before it added in the toCSS phase. so we need to work out
                        // what the resulting combinator will be
                        targetCombinator = haystackElement.combinator.value;
                        if (targetCombinator === '' && hackstackElementIndex === 0) {
                            targetCombinator = ' ';
                        }

                        // if we don't match, null our match to indicate failure
                        if (!extendVisitor.isElementValuesEqual(needleElements[potentialMatch.matched].value, haystackElement.value) ||
                            (potentialMatch.matched > 0 && needleElements[potentialMatch.matched].combinator.value !== targetCombinator)) {
                            potentialMatch = null;
                        } else {
                            potentialMatch.matched++;
                        }

                        // if we are still valid and have finished, test whether we have elements after and whether these are allowed
                        if (potentialMatch) {
                            potentialMatch.finished = potentialMatch.matched === needleElements.length;
                            if (potentialMatch.finished &&
                                (!extend.allowAfter && (hackstackElementIndex+1 < hackstackSelector.elements.length || haystackSelectorIndex+1 < haystackSelectorPath.length))) {
                                potentialMatch = null;
                            }
                        }
                        // if null we remove, if not, we are still valid, so either push as a valid match or continue
                        if (potentialMatch) {
                            if (potentialMatch.finished) {
                                potentialMatch.length = needleElements.length;
                                potentialMatch.endPathIndex = haystackSelectorIndex;
                                potentialMatch.endPathElementIndex = hackstackElementIndex + 1; // index after end of match
                                potentialMatches.length = 0; // we don't allow matches to overlap, so start matching again
                                matches.push(potentialMatch);
                            }
                        } else {
                            potentialMatches.splice(i, 1);
                            i--;
                        }
                    }
                }
            }
            return matches;
        },
        isElementValuesEqual: function(elementValue1, elementValue2) {
            if (typeof elementValue1 === "string" || typeof elementValue2 === "string") {
                return elementValue1 === elementValue2;
            }
            if (elementValue1 instanceof tree.Attribute) {
                if (elementValue1.op !== elementValue2.op || elementValue1.key !== elementValue2.key) {
                    return false;
                }
                if (!elementValue1.value || !elementValue2.value) {
                    if (elementValue1.value || elementValue2.value) {
                        return false;
                    }
                    return true;
                }
                elementValue1 = elementValue1.value.value || elementValue1.value;
                elementValue2 = elementValue2.value.value || elementValue2.value;
                return elementValue1 === elementValue2;
            }
            elementValue1 = elementValue1.value;
            elementValue2 = elementValue2.value;
            if (elementValue1 instanceof tree.Selector) {
                if (!(elementValue2 instanceof tree.Selector) || elementValue1.elements.length !== elementValue2.elements.length) {
                    return false;
                }
                for(var i = 0; i <elementValue1.elements.length; i++) {
                    if (elementValue1.elements[i].combinator.value !== elementValue2.elements[i].combinator.value) {
                        if (i !== 0 || (elementValue1.elements[i].combinator.value || ' ') !== (elementValue2.elements[i].combinator.value || ' ')) {
                            return false;
                        }
                    }
                    if (!this.isElementValuesEqual(elementValue1.elements[i].value, elementValue2.elements[i].value)) {
                        return false;
                    }
                }
                return true;
            }
            return false;
        },
        extendSelector:function (matches, selectorPath, replacementSelector) {

            //for a set of matches, replace each match with the replacement selector

            var currentSelectorPathIndex = 0,
                currentSelectorPathElementIndex = 0,
                path = [],
                matchIndex,
                selector,
                firstElement,
                match,
                newElements;

            for (matchIndex = 0; matchIndex < matches.length; matchIndex++) {
                match = matches[matchIndex];
                selector = selectorPath[match.pathIndex];
                firstElement = new tree.Element(
                    match.initialCombinator,
                    replacementSelector.elements[0].value,
                    replacementSelector.elements[0].index,
                    replacementSelector.elements[0].currentFileInfo
                );

                if (match.pathIndex > currentSelectorPathIndex && currentSelectorPathElementIndex > 0) {
                    path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                    currentSelectorPathElementIndex = 0;
                    currentSelectorPathIndex++;
                }

                newElements = selector.elements
                    .slice(currentSelectorPathElementIndex, match.index)
                    .concat([firstElement])
                    .concat(replacementSelector.elements.slice(1));

                if (currentSelectorPathIndex === match.pathIndex && matchIndex > 0) {
                    path[path.length - 1].elements =
                        path[path.length - 1].elements.concat(newElements);
                } else {
                    path = path.concat(selectorPath.slice(currentSelectorPathIndex, match.pathIndex));

                    path.push(new tree.Selector(
                        newElements
                    ));
                }
                currentSelectorPathIndex = match.endPathIndex;
                currentSelectorPathElementIndex = match.endPathElementIndex;
                if (currentSelectorPathElementIndex >= selectorPath[currentSelectorPathIndex].elements.length) {
                    currentSelectorPathElementIndex = 0;
                    currentSelectorPathIndex++;
                }
            }

            if (currentSelectorPathIndex < selectorPath.length && currentSelectorPathElementIndex > 0) {
                path[path.length - 1].elements = path[path.length - 1].elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                currentSelectorPathIndex++;
            }

            path = path.concat(selectorPath.slice(currentSelectorPathIndex, selectorPath.length));

            return path;
        },
        visitRulesetOut: function (rulesetNode) {
        },
        visitMedia: function (mediaNode, visitArgs) {
            var newAllExtends = mediaNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
            newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, mediaNode.allExtends));
            this.allExtendsStack.push(newAllExtends);
        },
        visitMediaOut: function (mediaNode) {
            this.allExtendsStack.length = this.allExtendsStack.length - 1;
        },
        visitDirective: function (directiveNode, visitArgs) {
            var newAllExtends = directiveNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length-1]);
            newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, directiveNode.allExtends));
            this.allExtendsStack.push(newAllExtends);
        },
        visitDirectiveOut: function (directiveNode) {
            this.allExtendsStack.length = this.allExtendsStack.length - 1;
        }
    };

})(require('./tree'));

(function (tree) {

    tree.sourceMapOutput = function (options) {
        this._css = [];
        this._rootNode = options.rootNode;
        this._writeSourceMap = options.writeSourceMap;
        this._contentsMap = options.contentsMap;
        this._contentsIgnoredCharsMap = options.contentsIgnoredCharsMap;
        this._sourceMapFilename = options.sourceMapFilename;
        this._outputFilename = options.outputFilename;
        this._sourceMapURL = options.sourceMapURL;
        if (options.sourceMapBasepath) {
            this._sourceMapBasepath = options.sourceMapBasepath.replace(/\\/g, '/');
        }
        this._sourceMapRootpath = options.sourceMapRootpath;
        this._outputSourceFiles = options.outputSourceFiles;
        this._sourceMapGeneratorConstructor = options.sourceMapGenerator || require("source-map").SourceMapGenerator;

        if (this._sourceMapRootpath && this._sourceMapRootpath.charAt(this._sourceMapRootpath.length-1) !== '/') {
            this._sourceMapRootpath += '/';
        }

        this._lineNumber = 0;
        this._column = 0;
    };

    tree.sourceMapOutput.prototype.normalizeFilename = function(filename) {
        filename = filename.replace(/\\/g, '/');

        if (this._sourceMapBasepath && filename.indexOf(this._sourceMapBasepath) === 0) {
            filename = filename.substring(this._sourceMapBasepath.length);
            if (filename.charAt(0) === '\\' || filename.charAt(0) === '/') {
               filename = filename.substring(1);
            }
        }
        return (this._sourceMapRootpath || "") + filename;
    };

    tree.sourceMapOutput.prototype.add = function(chunk, fileInfo, index, mapLines) {

        //ignore adding empty strings
        if (!chunk) {
            return;
        }

        var lines,
            sourceLines,
            columns,
            sourceColumns,
            i;

        if (fileInfo) {
            var inputSource = this._contentsMap[fileInfo.filename];
            
            // remove vars/banner added to the top of the file
            if (this._contentsIgnoredCharsMap[fileInfo.filename]) {
                // adjust the index
                index -= this._contentsIgnoredCharsMap[fileInfo.filename];
                if (index < 0) { index = 0; }
                // adjust the source
                inputSource = inputSource.slice(this._contentsIgnoredCharsMap[fileInfo.filename]);
            }
            inputSource = inputSource.substring(0, index);
            sourceLines = inputSource.split("\n");
            sourceColumns = sourceLines[sourceLines.length-1];
        }

        lines = chunk.split("\n");
        columns = lines[lines.length-1];

        if (fileInfo) {
            if (!mapLines) {
                this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + 1, column: this._column},
                    original: { line: sourceLines.length, column: sourceColumns.length},
                    source: this.normalizeFilename(fileInfo.filename)});
            } else {
                for(i = 0; i < lines.length; i++) {
                    this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + i + 1, column: i === 0 ? this._column : 0},
                        original: { line: sourceLines.length + i, column: i === 0 ? sourceColumns.length : 0},
                        source: this.normalizeFilename(fileInfo.filename)});
                }
            }
        }

        if (lines.length === 1) {
            this._column += columns.length;
        } else {
            this._lineNumber += lines.length - 1;
            this._column = columns.length;
        }

        this._css.push(chunk);
    };

    tree.sourceMapOutput.prototype.isEmpty = function() {
        return this._css.length === 0;
    };

    tree.sourceMapOutput.prototype.toCSS = function(env) {
        this._sourceMapGenerator = new this._sourceMapGeneratorConstructor({ file: this._outputFilename, sourceRoot: null });

        if (this._outputSourceFiles) {
            for(var filename in this._contentsMap) {
                if (this._contentsMap.hasOwnProperty(filename))
                {
                    var source = this._contentsMap[filename];
                    if (this._contentsIgnoredCharsMap[filename]) {
                        source = source.slice(this._contentsIgnoredCharsMap[filename]);
                    }
                    this._sourceMapGenerator.setSourceContent(this.normalizeFilename(filename), source);
                }
            }
        }

        this._rootNode.genCSS(env, this);

        if (this._css.length > 0) {
            var sourceMapURL,
                sourceMapContent = JSON.stringify(this._sourceMapGenerator.toJSON());

            if (this._sourceMapURL) {
                sourceMapURL = this._sourceMapURL;
            } else if (this._sourceMapFilename) {
                sourceMapURL = this.normalizeFilename(this._sourceMapFilename);
            }

            if (this._writeSourceMap) {
                this._writeSourceMap(sourceMapContent);
            } else {
                sourceMapURL = "data:application/json," + encodeURIComponent(sourceMapContent);
            }

            if (sourceMapURL) {
                this._css.push("/*# sourceMappingURL=" + sourceMapURL + " */");
            }
        }

        return this._css.join('');
    };

})(require('./tree'));

//
// browser.js - client-side engine
//
/*global less, window, document, XMLHttpRequest, location */

var isFileProtocol = /^(file|chrome(-extension)?|resource|qrc|app):/.test(location.protocol);

less.env = less.env || (location.hostname == '127.0.0.1' ||
                        location.hostname == '0.0.0.0'   ||
                        location.hostname == 'localhost' ||
                        (location.port &&
                          location.port.length > 0)      ||
                        isFileProtocol                   ? 'development'
                                                         : 'production');

var logLevel = {
    info: 2,
    errors: 1,
    none: 0
};

// The amount of logging in the javascript console.
// 2 - Information and errors
// 1 - Errors
// 0 - None
// Defaults to 2
less.logLevel = typeof(less.logLevel) != 'undefined' ? less.logLevel : logLevel.info;

// Load styles asynchronously (default: false)
//
// This is set to `false` by default, so that the body
// doesn't start loading before the stylesheets are parsed.
// Setting this to `true` can result in flickering.
//
less.async = less.async || false;
less.fileAsync = less.fileAsync || false;

// Interval between watch polls
less.poll = less.poll || (isFileProtocol ? 1000 : 1500);

//Setup user functions
if (less.functions) {
    for(var func in less.functions) {
        if (less.functions.hasOwnProperty(func)) {
            less.tree.functions[func] = less.functions[func];
        }
   }
}

var dumpLineNumbers = /!dumpLineNumbers:(comments|mediaquery|all)/.exec(location.hash);
if (dumpLineNumbers) {
    less.dumpLineNumbers = dumpLineNumbers[1];
}

var typePattern = /^text\/(x-)?less$/;
var cache = null;
var fileCache = {};

function log(str, level) {
    if (less.env == 'development' && typeof(console) !== 'undefined' && less.logLevel >= level) {
        console.log('less: ' + str);
    }
}

function extractId(href) {
    return href.replace(/^[a-z-]+:\/+?[^\/]+/, '' )  // Remove protocol & domain
        .replace(/^\//,                 '' )  // Remove root /
        .replace(/\.[a-zA-Z]+$/,        '' )  // Remove simple extension
        .replace(/[^\.\w-]+/g,          '-')  // Replace illegal characters
        .replace(/\./g,                 ':'); // Replace dots with colons(for valid id)
}

function errorConsole(e, rootHref) {
    var template = '{line} {content}';
    var filename = e.filename || rootHref;
    var errors = [];
    var content = (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
        " in " + filename + " ";

    var errorline = function (e, i, classname) {
        if (e.extract[i] !== undefined) {
            errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                .replace(/\{class\}/, classname)
                .replace(/\{content\}/, e.extract[i]));
        }
    };

    if (e.extract) {
        errorline(e, 0, '');
        errorline(e, 1, 'line');
        errorline(e, 2, '');
        content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':\n' +
            errors.join('\n');
    } else if (e.stack) {
        content += e.stack;
    }
    log(content, logLevel.errors);
}

function createCSS(styles, sheet, lastModified) {
    // Strip the query-string
    var href = sheet.href || '';

    // If there is no title set, use the filename, minus the extension
    var id = 'less:' + (sheet.title || extractId(href));

    // If this has already been inserted into the DOM, we may need to replace it
    var oldCss = document.getElementById(id);
    var keepOldCss = false;

    // Create a new stylesheet node for insertion or (if necessary) replacement
    var css = document.createElement('style');
    css.setAttribute('type', 'text/css');
    if (sheet.media) {
        css.setAttribute('media', sheet.media);
    }
    css.id = id;

    if (css.styleSheet) { // IE
        try {
            css.styleSheet.cssText = styles;
        } catch (e) {
            throw new(Error)("Couldn't reassign styleSheet.cssText.");
        }
    } else {
        css.appendChild(document.createTextNode(styles));

        // If new contents match contents of oldCss, don't replace oldCss
        keepOldCss = (oldCss !== null && oldCss.childNodes.length > 0 && css.childNodes.length > 0 &&
            oldCss.firstChild.nodeValue === css.firstChild.nodeValue);
    }

    var head = document.getElementsByTagName('head')[0];

    // If there is no oldCss, just append; otherwise, only append if we need
    // to replace oldCss with an updated stylesheet
    if (oldCss === null || keepOldCss === false) {
        var nextEl = sheet && sheet.nextSibling || null;
        if (nextEl) {
            nextEl.parentNode.insertBefore(css, nextEl);
        } else {
            head.appendChild(css);
        }
    }
    if (oldCss && keepOldCss === false) {
        oldCss.parentNode.removeChild(oldCss);
    }

    // Don't update the local store if the file wasn't modified
    if (lastModified && cache) {
        log('saving ' + href + ' to cache.', logLevel.info);
        try {
            cache.setItem(href, styles);
            cache.setItem(href + ':timestamp', lastModified);
        } catch(e) {
            //TODO - could do with adding more robust error handling
            log('failed to save', logLevel.errors);
        }
    }
}

function errorHTML(e, rootHref) {
    var id = 'less-error-message:' + extractId(rootHref || "");
    var template = '<li><label>{line}</label><pre class="{class}">{content}</pre></li>';
    var elem = document.createElement('div'), timer, content, errors = [];
    var filename = e.filename || rootHref;
    var filenameNoPath = filename.match(/([^\/]+(\?.*)?)$/)[1];

    elem.id        = id;
    elem.className = "less-error-message";

    content = '<h3>'  + (e.type || "Syntax") + "Error: " + (e.message || 'There is an error in your .less file') +
        '</h3>' + '<p>in <a href="' + filename   + '">' + filenameNoPath + "</a> ";

    var errorline = function (e, i, classname) {
        if (e.extract[i] !== undefined) {
            errors.push(template.replace(/\{line\}/, (parseInt(e.line, 10) || 0) + (i - 1))
                .replace(/\{class\}/, classname)
                .replace(/\{content\}/, e.extract[i]));
        }
    };

    if (e.extract) {
        errorline(e, 0, '');
        errorline(e, 1, 'line');
        errorline(e, 2, '');
        content += 'on line ' + e.line + ', column ' + (e.column + 1) + ':</p>' +
            '<ul>' + errors.join('') + '</ul>';
    } else if (e.stack) {
        content += '<br/>' + e.stack.split('\n').slice(1).join('<br/>');
    }
    elem.innerHTML = content;

    // CSS for error messages
    createCSS([
        '.less-error-message ul, .less-error-message li {',
        'list-style-type: none;',
        'margin-right: 15px;',
        'padding: 4px 0;',
        'margin: 0;',
        '}',
        '.less-error-message label {',
        'font-size: 12px;',
        'margin-right: 15px;',
        'padding: 4px 0;',
        'color: #cc7777;',
        '}',
        '.less-error-message pre {',
        'color: #dd6666;',
        'padding: 4px 0;',
        'margin: 0;',
        'display: inline-block;',
        '}',
        '.less-error-message pre.line {',
        'color: #ff0000;',
        '}',
        '.less-error-message h3 {',
        'font-size: 20px;',
        'font-weight: bold;',
        'padding: 15px 0 5px 0;',
        'margin: 0;',
        '}',
        '.less-error-message a {',
        'color: #10a',
        '}',
        '.less-error-message .error {',
        'color: red;',
        'font-weight: bold;',
        'padding-bottom: 2px;',
        'border-bottom: 1px dashed red;',
        '}'
    ].join('\n'), { title: 'error-message' });

    elem.style.cssText = [
        "font-family: Arial, sans-serif",
        "border: 1px solid #e00",
        "background-color: #eee",
        "border-radius: 5px",
        "-webkit-border-radius: 5px",
        "-moz-border-radius: 5px",
        "color: #e00",
        "padding: 15px",
        "margin-bottom: 15px"
    ].join(';');

    if (less.env == 'development') {
        timer = setInterval(function () {
            if (document.body) {
                if (document.getElementById(id)) {
                    document.body.replaceChild(elem, document.getElementById(id));
                } else {
                    document.body.insertBefore(elem, document.body.firstChild);
                }
                clearInterval(timer);
            }
        }, 10);
    }
}

function error(e, rootHref) {
    if (!less.errorReporting || less.errorReporting === "html") {
        errorHTML(e, rootHref);
    } else if (less.errorReporting === "console") {
        errorConsole(e, rootHref);
    } else if (typeof less.errorReporting === 'function') {
        less.errorReporting("add", e, rootHref);
    }
}

function removeErrorHTML(path) {
    var node = document.getElementById('less-error-message:' + extractId(path));
    if (node) {
        node.parentNode.removeChild(node);
    }
}

function removeErrorConsole(path) {
    //no action
}

function removeError(path) {
    if (!less.errorReporting || less.errorReporting === "html") {
        removeErrorHTML(path);
    } else if (less.errorReporting === "console") {
        removeErrorConsole(path);
    } else if (typeof less.errorReporting === 'function') {
        less.errorReporting("remove", path);
    }
}

function loadStyles(modifyVars) {
    var styles = document.getElementsByTagName('style'),
        style;
    for (var i = 0; i < styles.length; i++) {
        style = styles[i];
        if (style.type.match(typePattern)) {
            var env = new less.tree.parseEnv(less),
                lessText = style.innerHTML || '';
            env.filename = document.location.href.replace(/#.*$/, '');

            if (modifyVars || less.globalVars) {
                env.useFileCache = true;
            }

            /*jshint loopfunc:true */
            // use closure to store current value of i
            var callback = (function(style) {
                return function (e, cssAST) {
                    if (e) {
                        return error(e, "inline");
                    }
                    var css = cssAST.toCSS(less);
                    style.type = 'text/css';
                    if (style.styleSheet) {
                        style.styleSheet.cssText = css;
                    } else {
                        style.innerHTML = css;
                    }
                };
            })(style);
            new(less.Parser)(env).parse(lessText, callback, {globalVars: less.globalVars, modifyVars: modifyVars});
        }
    }
}

function extractUrlParts(url, baseUrl) {
    // urlParts[1] = protocol&hostname || /
    // urlParts[2] = / if path relative to host base
    // urlParts[3] = directories
    // urlParts[4] = filename
    // urlParts[5] = parameters

    var urlPartsRegex = /^((?:[a-z-]+:)?\/+?(?:[^\/\?#]*\/)|([\/\\]))?((?:[^\/\\\?#]*[\/\\])*)([^\/\\\?#]*)([#\?].*)?$/i,
        urlParts = url.match(urlPartsRegex),
        returner = {}, directories = [], i, baseUrlParts;

    if (!urlParts) {
        throw new Error("Could not parse sheet href - '"+url+"'");
    }

    // Stylesheets in IE don't always return the full path
    if (!urlParts[1] || urlParts[2]) {
        baseUrlParts = baseUrl.match(urlPartsRegex);
        if (!baseUrlParts) {
            throw new Error("Could not parse page url - '"+baseUrl+"'");
        }
        urlParts[1] = urlParts[1] || baseUrlParts[1] || "";
        if (!urlParts[2]) {
            urlParts[3] = baseUrlParts[3] + urlParts[3];
        }
    }

    if (urlParts[3]) {
        directories = urlParts[3].replace(/\\/g, "/").split("/");

        // extract out . before .. so .. doesn't absorb a non-directory
        for(i = 0; i < directories.length; i++) {
            if (directories[i] === ".") {
                directories.splice(i, 1);
                i -= 1;
            }
        }

        for(i = 0; i < directories.length; i++) {
            if (directories[i] === ".." && i > 0) {
                directories.splice(i-1, 2);
                i -= 2;
            }
        }
    }

    returner.hostPart = urlParts[1];
    returner.directories = directories;
    returner.path = urlParts[1] + directories.join("/");
    returner.fileUrl = returner.path + (urlParts[4] || "");
    returner.url = returner.fileUrl + (urlParts[5] || "");
    return returner;
}

function pathDiff(url, baseUrl) {
    // diff between two paths to create a relative path

    var urlParts = extractUrlParts(url),
        baseUrlParts = extractUrlParts(baseUrl),
        i, max, urlDirectories, baseUrlDirectories, diff = "";
    if (urlParts.hostPart !== baseUrlParts.hostPart) {
        return "";
    }
    max = Math.max(baseUrlParts.directories.length, urlParts.directories.length);
    for(i = 0; i < max; i++) {
        if (baseUrlParts.directories[i] !== urlParts.directories[i]) { break; }
    }
    baseUrlDirectories = baseUrlParts.directories.slice(i);
    urlDirectories = urlParts.directories.slice(i);
    for(i = 0; i < baseUrlDirectories.length-1; i++) {
        diff += "../";
    }
    for(i = 0; i < urlDirectories.length-1; i++) {
        diff += urlDirectories[i] + "/";
    }
    return diff;
}

function getXMLHttpRequest() {
    if (window.XMLHttpRequest) {
        return new XMLHttpRequest();
    } else {
        try {
            /*global ActiveXObject */
            return new ActiveXObject("MSXML2.XMLHTTP.3.0");
        } catch (e) {
            log("browser doesn't support AJAX.", logLevel.errors);
            return null;
        }
    }
}

function doXHR(url, type, callback, errback) {
    var xhr = getXMLHttpRequest();
    var async = isFileProtocol ? less.fileAsync : less.async;

    if (typeof(xhr.overrideMimeType) === 'function') {
        xhr.overrideMimeType('text/css');
    }
    log("XHR: Getting '" + url + "'", logLevel.info);
    xhr.open('GET', url, async);
    xhr.setRequestHeader('Accept', type || 'text/x-less, text/css; q=0.9, */*; q=0.5');
    xhr.send(null);

    function handleResponse(xhr, callback, errback) {
        if (xhr.status >= 200 && xhr.status < 300) {
            callback(xhr.responseText,
                xhr.getResponseHeader("Last-Modified"));
        } else if (typeof(errback) === 'function') {
            errback(xhr.status, url);
        }
    }

    if (isFileProtocol && !less.fileAsync) {
        if (xhr.status === 0 || (xhr.status >= 200 && xhr.status < 300)) {
            callback(xhr.responseText);
        } else {
            errback(xhr.status, url);
        }
    } else if (async) {
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4) {
                handleResponse(xhr, callback, errback);
            }
        };
    } else {
        handleResponse(xhr, callback, errback);
    }
}

function loadFile(originalHref, currentFileInfo, callback, env, modifyVars) {

    if (currentFileInfo && currentFileInfo.currentDirectory && !/^([a-z-]+:)?\//.test(originalHref)) {
        originalHref = currentFileInfo.currentDirectory + originalHref;
    }

    // sheet may be set to the stylesheet for the initial load or a collection of properties including
    // some env variables for imports
    var hrefParts = extractUrlParts(originalHref, window.location.href);
    var href      = hrefParts.url;
    var newFileInfo = {
        currentDirectory: hrefParts.path,
        filename: href
    };

    if (currentFileInfo) {
        newFileInfo.entryPath = currentFileInfo.entryPath;
        newFileInfo.rootpath = currentFileInfo.rootpath;
        newFileInfo.rootFilename = currentFileInfo.rootFilename;
        newFileInfo.relativeUrls = currentFileInfo.relativeUrls;
    } else {
        newFileInfo.entryPath = hrefParts.path;
        newFileInfo.rootpath = less.rootpath || hrefParts.path;
        newFileInfo.rootFilename = href;
        newFileInfo.relativeUrls = env.relativeUrls;
    }

    if (newFileInfo.relativeUrls) {
        if (env.rootpath) {
            newFileInfo.rootpath = extractUrlParts(env.rootpath + pathDiff(hrefParts.path, newFileInfo.entryPath)).path;
        } else {
            newFileInfo.rootpath = hrefParts.path;
        }
    }

    if (env.useFileCache && fileCache[href]) {
        try {
            var lessText = fileCache[href];
            callback(null, lessText, href, newFileInfo, { lastModified: new Date() });
        } catch (e) {
            callback(e, null, href);
        }
        return;
    }

    doXHR(href, env.mime, function (data, lastModified) {
        // per file cache
        fileCache[href] = data;

        // Use remote copy (re-parse)
        try {
            callback(null, data, href, newFileInfo, { lastModified: lastModified });
        } catch (e) {
            callback(e, null, href);
        }
    }, function (status, url) {
        callback({ type: 'File', message: "'" + url + "' wasn't found (" + status + ")" }, null, href);
    });
}

function loadStyleSheet(sheet, callback, reload, remaining, modifyVars) {

    var env = new less.tree.parseEnv(less);
    env.mime = sheet.type;

    if (modifyVars || less.globalVars) {
        env.useFileCache = true;
    }

    loadFile(sheet.href, null, function(e, data, path, newFileInfo, webInfo) {

        if (webInfo) {
            webInfo.remaining = remaining;

            var css       = cache && cache.getItem(path),
                timestamp = cache && cache.getItem(path + ':timestamp');

            if (!reload && timestamp && webInfo.lastModified &&
                (new(Date)(webInfo.lastModified).valueOf() ===
                    new(Date)(timestamp).valueOf())) {
                // Use local copy
                createCSS(css, sheet);
                webInfo.local = true;
                callback(null, null, data, sheet, webInfo, path);
                return;
            }
        }

        //TODO add tests around how this behaves when reloading
        removeError(path);

        if (data) {
            env.currentFileInfo = newFileInfo;
            new(less.Parser)(env).parse(data, function (e, root) {
                if (e) { return callback(e, null, null, sheet); }
                try {
                    callback(e, root, data, sheet, webInfo, path);
                } catch (e) {
                    callback(e, null, null, sheet);
                }
            }, {modifyVars: modifyVars, globalVars: less.globalVars});
        } else {
            callback(e, null, null, sheet, webInfo, path);
        }
    }, env, modifyVars);
}

function loadStyleSheets(callback, reload, modifyVars) {
    for (var i = 0; i < less.sheets.length; i++) {
        loadStyleSheet(less.sheets[i], callback, reload, less.sheets.length - (i + 1), modifyVars);
    }
}

function initRunningMode(){
    if (less.env === 'development') {
        less.optimization = 0;
        less.watchTimer = setInterval(function () {
            if (less.watchMode) {
                loadStyleSheets(function (e, root, _, sheet, env) {
                    if (e) {
                        error(e, sheet.href);
                    } else if (root) {
                        createCSS(root.toCSS(less), sheet, env.lastModified);
                    }
                });
            }
        }, less.poll);
    } else {
        less.optimization = 3;
    }
}



//
// Watch mode
//
less.watch   = function () {
    if (!less.watchMode ){
        less.env = 'development';
         initRunningMode();
    }
    this.watchMode = true;
    return true;
};

less.unwatch = function () {clearInterval(less.watchTimer); this.watchMode = false; return false; };

if (/!watch/.test(location.hash)) {
    less.watch();
}

if (less.env != 'development') {
    try {
        cache = (typeof(window.localStorage) === 'undefined') ? null : window.localStorage;
    } catch (_) {}
}

//
// Get all <link> tags with the 'rel' attribute set to "stylesheet/less"
//
var links = document.getElementsByTagName('link');

less.sheets = [];

for (var i = 0; i < links.length; i++) {
    if (links[i].rel === 'stylesheet/less' || (links[i].rel.match(/stylesheet/) &&
       (links[i].type.match(typePattern)))) {
        less.sheets.push(links[i]);
    }
}

//
// With this function, it's possible to alter variables and re-render
// CSS without reloading less-files
//
less.modifyVars = function(record) {
    less.refresh(false, record);
};

less.refresh = function (reload, modifyVars) {
    var startTime, endTime;
    startTime = endTime = new Date();

    loadStyleSheets(function (e, root, _, sheet, env) {
        if (e) {
            return error(e, sheet.href);
        }
        if (env.local) {
            log("loading " + sheet.href + " from cache.", logLevel.info);
        } else {
            log("parsed " + sheet.href + " successfully.", logLevel.info);
            createCSS(root.toCSS(less), sheet, env.lastModified);
        }
        log("css for " + sheet.href + " generated in " + (new Date() - endTime) + 'ms', logLevel.info);
        if (env.remaining === 0) {
            log("css generated in " + (new Date() - startTime) + 'ms', logLevel.info);
        }
        endTime = new Date();
    }, reload, modifyVars);

    loadStyles(modifyVars);
};

less.refreshStyles = loadStyles;

less.Parser.fileLoader = loadFile;

less.refresh(less.env === 'development');

// amd.js
//
// Define Less as an AMD module.
if (typeof define === "function" && define.amd) {
    define(function () { return less; } );
}

})(window);