// Copyright (c) 1999-2004 Brian Wellington (bwelling@xbill.org)

package org.xbill.DNS;

import java.io.*;
import java.text.*;

/**
 * A representation of a domain name.  It may either be absolute (fully
 * qualified) or relative.
 *
 * @author Brian Wellington
 */

public class Name implements Comparable, Serializable {

    private static final long serialVersionUID = -7257019940971525644L;

    private static final int LABEL_NORMAL = 0;
    private static final int LABEL_COMPRESSION = 0xC0;
    private static final int LABEL_MASK = 0xC0;

    /* The name data */
    private byte[] name;

    /*
     * Effectively an 8 byte array, where the low order byte stores the number
     * of labels and the 7 higher order bytes store per-label offsets.
     */
    private long offsets;

    /* Precomputed hashcode. */
    private int hashcode;

    private static final byte[] emptyLabel = new byte[]{(byte) 0};
    private static final byte[] wildLabel = new byte[]{(byte) 1, (byte) '*'};

    /**
     * The root name
     */
    public static final Name root;

    /**
     * The root name
     */
    public static final Name empty;

    /**
     * The maximum length of a Name
     */
    private static final int MAXNAME = 255;

    /**
     * The maximum length of a label a Name
     */
    private static final int MAXLABEL = 63;

    /**
     * The maximum number of labels in a Name
     */
    private static final int MAXLABELS = 128;

    /**
     * The maximum number of cached offsets
     */
    private static final int MAXOFFSETS = 7;

    /* Used for printing non-printable characters */
    private static final DecimalFormat byteFormat = new DecimalFormat();

    /* Used to efficiently convert bytes to lowercase */
    private static final byte lowercase[] = new byte[256];

    /* Used in wildcard names. */
    private static final Name wild;

    static {
        byteFormat.setMinimumIntegerDigits(3);
        for (int i = 0; i < lowercase.length; i++) {
            if (i < 'A' || i > 'Z')
                lowercase[i] = (byte) i;
            else
                lowercase[i] = (byte) (i - 'A' + 'a');
        }
        root = new Name();
        root.appendSafe(emptyLabel, 0, 1);
        empty = new Name();
        empty.name = new byte[0];
        wild = new Name();
        wild.appendSafe(wildLabel, 0, 1);
    }

    private Name() {
    }

    private final void
    setoffset(int n, int offset) {
        if (n >= MAXOFFSETS)
            return;
        int shift = 8 * (7 - n);
        offsets &= (~(0xFFL << shift));
        offsets |= ((long) offset << shift);
    }

    private final int
    offset(int n) {
        if (n == 0 && getlabels() == 0)
            return 0;
        if (n < 0 || n >= getlabels())
            throw new IllegalArgumentException("label out of range");
        if (n < MAXOFFSETS) {
            int shift = 8 * (7 - n);
            return ((int) (offsets >>> shift) & 0xFF);
        } else {
            int pos = offset(MAXOFFSETS - 1);
            for (int i = MAXOFFSETS - 1; i < n; i++)
                pos += (name[pos] + 1);
            return (pos);
        }
    }

    private final void
    setlabels(int labels) {
        offsets &= ~(0xFF);
        offsets |= labels;
    }

    private final int
    getlabels() {
        return (int) (offsets & 0xFF);
    }

    private static final void
    copy(Name src, Name dst) {
        if (src.offset(0) == 0) {
            dst.name = src.name;
            dst.offsets = src.offsets;
        } else {
            int offset0 = src.offset(0);
            int namelen = src.name.length - offset0;
            int labels = src.labels();
            dst.name = new byte[namelen];
            System.arraycopy(src.name, offset0, dst.name, 0, namelen);
            for (int i = 0; i < labels && i < MAXOFFSETS; i++)
                dst.setoffset(i, src.offset(i) - offset0);
            dst.setlabels(labels);
        }
    }

    private final void
    append(byte[] array, int start, int n) throws NameTooLongException {
        int length = (name == null ? 0 : (name.length - offset(0)));
        int alength = 0;
        for (int i = 0, pos = start; i < n; i++) {
            int len = array[pos];
            if (len > MAXLABEL)
                throw new IllegalStateException("invalid label");
            len++;
            pos += len;
            alength += len;
        }
        int newlength = length + alength;
        if (newlength > MAXNAME)
            throw new NameTooLongException();
        int labels = getlabels();
        int newlabels = labels + n;
        if (newlabels > MAXLABELS)
            throw new IllegalStateException("too many labels");
        byte[] newname = new byte[newlength];
        if (length != 0)
            System.arraycopy(name, offset(0), newname, 0, length);
        System.arraycopy(array, start, newname, length, alength);
        name = newname;
        for (int i = 0, pos = length; i < n; i++) {
            setoffset(labels + i, pos);
            pos += (newname[pos] + 1);
        }
        setlabels(newlabels);
    }

    private static TextParseException
    parseException(String str, String message) {
        return new TextParseException("'" + str + "': " + message);
    }

    private final void
    appendFromString(String fullName, byte[] array, int start, int n)
            throws TextParseException {
        try {
            append(array, start, n);
        } catch (NameTooLongException e) {
            throw parseException(fullName, "Name too long");
        }
    }

    private final void
    appendSafe(byte[] array, int start, int n) {
        try {
            append(array, start, n);
        } catch (NameTooLongException e) {
        }
    }

    /**
     * Create a new name from a string and an origin.  This does not automatically
     * make the name absolute; it will be absolute if it has a trailing dot or an
     * absolute origin is appended.
     *
     * @param s      The string to be converted
     * @param origin If the name is not absolute, the origin to be appended.
     * @throws TextParseException The name is invalid.
     */
    public Name(String s, Name origin) throws TextParseException {
        if (s.equals(""))
            throw parseException(s, "empty name");
        else if (s.equals("@")) {
            if (origin == null)
                copy(empty, this);
            else
                copy(origin, this);
            return;
        } else if (s.equals(".")) {
            copy(root, this);
            return;
        }
        int labelstart = -1;
        int pos = 1;
        byte[] label = new byte[MAXLABEL + 1];
        boolean escaped = false;
        int digits = 0;
        int intval = 0;
        boolean absolute = false;
        for (int i = 0; i < s.length(); i++) {
            byte b = (byte) s.charAt(i);
            if (escaped) {
                if (b >= '0' && b <= '9' && digits < 3) {
                    digits++;
                    intval *= 10;
                    intval += (b - '0');
                    if (intval > 255)
                        throw parseException(s, "bad escape");
                    if (digits < 3)
                        continue;
                    b = (byte) intval;
                } else if (digits > 0 && digits < 3)
                    throw parseException(s, "bad escape");
                if (pos > MAXLABEL)
                    throw parseException(s, "label too long");
                labelstart = pos;
                label[pos++] = b;
                escaped = false;
            } else if (b == '\\') {
                escaped = true;
                digits = 0;
                intval = 0;
            } else if (b == '.') {
                if (labelstart == -1)
                    throw parseException(s, "invalid empty label");
                label[0] = (byte) (pos - 1);
                appendFromString(s, label, 0, 1);
                labelstart = -1;
                pos = 1;
            } else {
                if (labelstart == -1)
                    labelstart = i;
                if (pos > MAXLABEL)
                    throw parseException(s, "label too long");
                label[pos++] = b;
            }
        }
        if (digits > 0 && digits < 3)
            throw parseException(s, "bad escape");
        if (escaped)
            throw parseException(s, "bad escape");
        if (labelstart == -1) {
            appendFromString(s, emptyLabel, 0, 1);
            absolute = true;
        } else {
            label[0] = (byte) (pos - 1);
            appendFromString(s, label, 0, 1);
        }
        if (origin != null && !absolute)
            appendFromString(s, origin.name, 0, origin.getlabels());
    }

    /**
     * Create a new name from a string.  This does not automatically make the name
     * absolute; it will be absolute if it has a trailing dot.
     *
     * @param s The string to be converted
     * @throws TextParseException The name is invalid.
     */
    public Name(String s) throws TextParseException {
        this(s, null);
    }

    /**
     * Create a new name from a string and an origin.  This does not automatically
     * make the name absolute; it will be absolute if it has a trailing dot or an
     * absolute origin is appended.  This is identical to the constructor, except
     * that it will avoid creating new objects in some cases.
     *
     * @param s      The string to be converted
     * @param origin If the name is not absolute, the origin to be appended.
     * @throws TextParseException The name is invalid.
     */
    public static Name
    fromString(String s, Name origin) throws TextParseException {
        if (s.equals("@") && origin != null)
            return origin;
        else if (s.equals("."))
            return (root);

        return new Name(s, origin);
    }

    /**
     * Create a new name from a string.  This does not automatically make the name
     * absolute; it will be absolute if it has a trailing dot.  This is identical
     * to the constructor, except that it will avoid creating new objects in some
     * cases.
     *
     * @param s The string to be converted
     * @throws TextParseException The name is invalid.
     */
    public static Name
    fromString(String s) throws TextParseException {
        return fromString(s, null);
    }

    /**
     * Create a new name from a constant string.  This should only be used when
     * the name is known to be good - that is, when it is constant.
     *
     * @param s The string to be converted
     * @throws IllegalArgumentException The name is invalid.
     */
    public static Name
    fromConstantString(String s) {
        try {
            return fromString(s, null);
        } catch (TextParseException e) {
            throw new IllegalArgumentException("Invalid name '" + s + "'");
        }
    }

    /**
     * Create a new name from DNS a wire format message
     *
     * @param in A stream containing the DNS message which is currently
     *           positioned at the start of the name to be read.
     */
    public Name(DNSInput in) throws WireParseException {
        int len, pos;
        boolean done = false;
        byte[] label = new byte[MAXLABEL + 1];
        boolean savedState = false;

        while (!done) {
            len = in.readU8();
            switch (len & LABEL_MASK) {
                case LABEL_NORMAL:
                    if (getlabels() >= MAXLABELS)
                        throw new WireParseException("too many labels");
                    if (len == 0) {
                        append(emptyLabel, 0, 1);
                        done = true;
                    } else {
                        label[0] = (byte) len;
                        in.readByteArray(label, 1, len);
                        append(label, 0, 1);
                    }
                    break;
                case LABEL_COMPRESSION:
                    pos = in.readU8();
                    pos += ((len & ~LABEL_MASK) << 8);
                    if (Options.check("verbosecompression"))
                        System.err.println("currently " + in.current() +
                                ", pointer to " + pos);

                    if (pos >= in.current() - 2)
                        throw new WireParseException("bad compression");
                    if (!savedState) {
                        in.save();
                        savedState = true;
                    }
                    in.jump(pos);
                    if (Options.check("verbosecompression"))
                        System.err.println("current name '" + this +
                                "', seeking to " + pos);
                    break;
                default:
                    throw new WireParseException("bad label type");
            }
        }
        if (savedState) {
            in.restore();
        }
    }

    /**
     * Create a new name from DNS wire format
     *
     * @param b A byte array containing the wire format of the name.
     */
    public Name(byte[] b) throws IOException {
        this(new DNSInput(b));
    }

    /**
     * Create a new name by removing labels from the beginning of an existing Name
     *
     * @param src An existing Name
     * @param n   The number of labels to remove from the beginning in the copy
     */
    public Name(Name src, int n) {
        int slabels = src.labels();
        if (n > slabels)
            throw new IllegalArgumentException("attempted to remove too " +
                    "many labels");
        name = src.name;
        setlabels(slabels - n);
        for (int i = 0; i < MAXOFFSETS && i < slabels - n; i++)
            setoffset(i, src.offset(i + n));
    }

    /**
     * Creates a new name by concatenating two existing names.
     *
     * @param prefix The prefix name.
     * @param suffix The suffix name.
     * @return The concatenated name.
     * @throws NameTooLongException The name is too long.
     */
    public static Name
    concatenate(Name prefix, Name suffix) throws NameTooLongException {
        if (prefix.isAbsolute())
            return (prefix);
        Name newname = new Name();
        copy(prefix, newname);
        newname.append(suffix.name, suffix.offset(0), suffix.getlabels());
        return newname;
    }

    /**
     * If this name is a subdomain of origin, return a new name relative to
     * origin with the same value. Otherwise, return the existing name.
     *
     * @param origin The origin to remove.
     * @return The possibly relativized name.
     */
    public Name
    relativize(Name origin) {
        if (origin == null || !subdomain(origin))
            return this;
        Name newname = new Name();
        copy(this, newname);
        int length = length() - origin.length();
        int labels = newname.labels() - origin.labels();
        newname.setlabels(labels);
        newname.name = new byte[length];
        System.arraycopy(name, offset(0), newname.name, 0, length);
        return newname;
    }

    /**
     * Generates a new Name with the first n labels replaced by a wildcard
     *
     * @return The wildcard name
     */
    public Name
    wild(int n) {
        if (n < 1)
            throw new IllegalArgumentException("must replace 1 or more " +
                    "labels");
        try {
            Name newname = new Name();
            copy(wild, newname);
            newname.append(name, offset(n), getlabels() - n);
            return newname;
        } catch (NameTooLongException e) {
            throw new IllegalStateException
                    ("Name.wild: concatenate failed");
        }
    }

    /**
     * Generates a new Name to be used when following a DNAME.
     *
     * @param dname The DNAME record to follow.
     * @return The constructed name.
     * @throws NameTooLongException The resulting name is too long.
     */
    public Name
    fromDNAME(DNAMERecord dname) throws NameTooLongException {
        Name dnameowner = dname.getName();
        Name dnametarget = dname.getTarget();
        if (!subdomain(dnameowner))
            return null;

        int plabels = labels() - dnameowner.labels();
        int plength = length() - dnameowner.length();
        int pstart = offset(0);

        int dlabels = dnametarget.labels();
        int dlength = dnametarget.length();

        if (plength + dlength > MAXNAME)
            throw new NameTooLongException();

        Name newname = new Name();
        newname.setlabels(plabels + dlabels);
        newname.name = new byte[plength + dlength];
        System.arraycopy(name, pstart, newname.name, 0, plength);
        System.arraycopy(dnametarget.name, 0, newname.name, plength, dlength);

        for (int i = 0, pos = 0; i < MAXOFFSETS && i < plabels + dlabels; i++) {
            newname.setoffset(i, pos);
            pos += (newname.name[pos] + 1);
        }
        return newname;
    }

    /**
     * Is this name a wildcard?
     */
    public boolean
    isWild() {
        if (labels() == 0)
            return false;
        return (name[0] == (byte) 1 && name[1] == (byte) '*');
    }

    /**
     * Is this name absolute?
     */
    public boolean
    isAbsolute() {
        if (labels() == 0)
            return false;
        return (name[name.length - 1] == 0);
    }

    /**
     * The length of the name.
     */
    public short
    length() {
        if (getlabels() == 0)
            return 0;
        return (short) (name.length - offset(0));
    }

    /**
     * The number of labels in the name.
     */
    public int
    labels() {
        return getlabels();
    }

    /**
     * Is the current Name a subdomain of the specified name?
     */
    public boolean
    subdomain(Name domain) {
        int labels = labels();
        int dlabels = domain.labels();
        if (dlabels > labels)
            return false;
        if (dlabels == labels)
            return equals(domain);
        return domain.equals(name, offset(labels - dlabels));
    }

    private String
    byteString(byte[] array, int pos) {
        StringBuffer sb = new StringBuffer();
        int len = array[pos++];
        for (int i = pos; i < pos + len; i++) {
            int b = array[i] & 0xFF;
            if (b <= 0x20 || b >= 0x7f) {
                sb.append('\\');
                sb.append(byteFormat.format(b));
            } else if (b == '"' || b == '(' || b == ')' || b == '.' ||
                    b == ';' || b == '\\' || b == '@' || b == '$') {
                sb.append('\\');
                sb.append((char) b);
            } else
                sb.append((char) b);
        }
        return sb.toString();
    }

    /**
     * Convert a Name to a String
     *
     * @return The representation of this name as a (printable) String.
     */
    public String
    toString() {
        int labels = labels();
        if (labels == 0)
            return "@";
        else if (labels == 1 && name[offset(0)] == 0)
            return ".";
        StringBuffer sb = new StringBuffer();
        for (int i = 0, pos = offset(0); i < labels; i++) {
            int len = name[pos];
            if (len > MAXLABEL)
                throw new IllegalStateException("invalid label");
            if (len == 0)
                break;
            sb.append(byteString(name, pos));
            sb.append('.');
            pos += (1 + len);
        }
        if (!isAbsolute())
            sb.deleteCharAt(sb.length() - 1);
        return sb.toString();
    }

    /**
     * Retrieve the nth label of a Name.  This makes a copy of the label; changing
     * this does not change the Name.
     *
     * @param n The label to be retrieved.  The first label is 0.
     */
    public byte[]
    getLabel(int n) {
        int pos = offset(n);
        byte len = (byte) (name[pos] + 1);
        byte[] label = new byte[len];
        System.arraycopy(name, pos, label, 0, len);
        return label;
    }

    /**
     * Convert the nth label in a Name to a String
     *
     * @param n The label to be converted to a (printable) String.  The first
     *          label is 0.
     */
    public String
    getLabelString(int n) {
        int pos = offset(n);
        return byteString(name, pos);
    }

    /**
     * Emit a Name in DNS wire format
     *
     * @param out The output stream containing the DNS message.
     * @param c   The compression context, or null of no compression is desired.
     * @throws IllegalArgumentException The name is not absolute.
     */
    public void
    toWire(DNSOutput out, Compression c) {
        if (!isAbsolute())
            throw new IllegalArgumentException("toWire() called on " +
                    "non-absolute name");

        int labels = labels();
        for (int i = 0; i < labels - 1; i++) {
            Name tname;
            if (i == 0)
                tname = this;
            else
                tname = new Name(this, i);
            int pos = -1;
            if (c != null)
                pos = c.get(tname);
            if (pos >= 0) {
                pos |= (LABEL_MASK << 8);
                out.writeU16(pos);
                return;
            } else {
                if (c != null)
                    c.add(out.current(), tname);
                int off = offset(i);
                out.writeByteArray(name, off, name[off] + 1);
            }
        }
        out.writeU8(0);
    }

    /**
     * Emit a Name in DNS wire format
     *
     * @throws IllegalArgumentException The name is not absolute.
     */
    public byte[]
    toWire() {
        DNSOutput out = new DNSOutput();
        toWire(out, null);
        return out.toByteArray();
    }

    /**
     * Emit a Name in canonical DNS wire format (all lowercase)
     *
     * @param out The output stream to which the message is written.
     */
    public void
    toWireCanonical(DNSOutput out) {
        byte[] b = toWireCanonical();
        out.writeByteArray(b);
    }

    /**
     * Emit a Name in canonical DNS wire format (all lowercase)
     *
     * @return The canonical form of the name.
     */
    public byte[]
    toWireCanonical() {
        int labels = labels();
        if (labels == 0)
            return (new byte[0]);
        byte[] b = new byte[name.length - offset(0)];
        for (int i = 0, spos = offset(0), dpos = 0; i < labels; i++) {
            int len = name[spos];
            if (len > MAXLABEL)
                throw new IllegalStateException("invalid label");
            b[dpos++] = name[spos++];
            for (int j = 0; j < len; j++)
                b[dpos++] = lowercase[(name[spos++] & 0xFF)];
        }
        return b;
    }

    /**
     * Emit a Name in DNS wire format
     *
     * @param out       The output stream containing the DNS message.
     * @param c         The compression context, or null of no compression is desired.
     * @param canonical If true, emit the name in canonicalized form
     *                  (all lowercase).
     * @throws IllegalArgumentException The name is not absolute.
     */
    public void
    toWire(DNSOutput out, Compression c, boolean canonical) {
        if (canonical)
            toWireCanonical(out);
        else
            toWire(out, c);
    }

    private final boolean
    equals(byte[] b, int bpos) {
        int labels = labels();
        for (int i = 0, pos = offset(0); i < labels; i++) {
            if (name[pos] != b[bpos])
                return false;
            int len = name[pos++];
            bpos++;
            if (len > MAXLABEL)
                throw new IllegalStateException("invalid label");
            for (int j = 0; j < len; j++)
                if (lowercase[(name[pos++] & 0xFF)] !=
                        lowercase[(b[bpos++] & 0xFF)])
                    return false;
        }
        return true;
    }

    /**
     * Are these two Names equivalent?
     */
    public boolean
    equals(Object arg) {
        if (arg == this)
            return true;
        if (arg == null || !(arg instanceof Name))
            return false;
        Name d = (Name) arg;
        if (d.hashcode == 0)
            d.hashCode();
        if (hashcode == 0)
            hashCode();
        if (d.hashcode != hashcode)
            return false;
        if (d.labels() != labels())
            return false;
        return equals(d.name, d.offset(0));
    }

    /**
     * Computes a hashcode based on the value
     */
    public int
    hashCode() {
        if (hashcode != 0)
            return (hashcode);
        int code = 0;
        for (int i = offset(0); i < name.length; i++)
            code += ((code << 3) + lowercase[(name[i] & 0xFF)]);
        hashcode = code;
        return hashcode;
    }

    /**
     * Compares this Name to another Object.
     *
     * @param o The Object to be compared.
     * @return The value 0 if the argument is a name equivalent to this name;
     * a value less than 0 if the argument is less than this name in the canonical
     * ordering, and a value greater than 0 if the argument is greater than this
     * name in the canonical ordering.
     * @throws ClassCastException if the argument is not a Name.
     */
    public int
    compareTo(Object o) {
        Name arg = (Name) o;

        if (this == arg)
            return (0);

        int labels = labels();
        int alabels = arg.labels();
        int compares = labels > alabels ? alabels : labels;

        for (int i = 1; i <= compares; i++) {
            int start = offset(labels - i);
            int astart = arg.offset(alabels - i);
            int length = name[start];
            int alength = arg.name[astart];
            for (int j = 0; j < length && j < alength; j++) {
                int n = lowercase[(name[j + start + 1]) & 0xFF] -
                        lowercase[(arg.name[j + astart + 1]) & 0xFF];
                if (n != 0)
                    return (n);
            }
            if (length != alength)
                return (length - alength);
        }
        return (labels - alabels);
    }

}
