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

package org.xbill.DNS.utils;

import java.io.*;

/**
 * Routines for converting between Strings of base64-encoded data and arrays of
 * binary data.
 *
 * @author Brian Wellington
 */

public class base64 {

    private static final String Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    private base64() {
    }

    /**
     * Convert binary data to a base64-encoded String
     *
     * @param b An array containing binary data
     * @return A String containing the encoded data
     */
    public static String
    toString(byte[] b) {
        ByteArrayOutputStream os = new ByteArrayOutputStream();

        for (int i = 0; i < (b.length + 2) / 3; i++) {
            short[] s = new short[3];
            short[] t = new short[4];
            for (int j = 0; j < 3; j++) {
                if ((i * 3 + j) < b.length)
                    s[j] = (short) (b[i * 3 + j] & 0xFF);
                else
                    s[j] = -1;
            }

            t[0] = (short) (s[0] >> 2);
            if (s[1] == -1)
                t[1] = (short) (((s[0] & 0x3) << 4));
            else
                t[1] = (short) (((s[0] & 0x3) << 4) + (s[1] >> 4));
            if (s[1] == -1)
                t[2] = t[3] = 64;
            else if (s[2] == -1) {
                t[2] = (short) (((s[1] & 0xF) << 2));
                t[3] = 64;
            } else {
                t[2] = (short) (((s[1] & 0xF) << 2) + (s[2] >> 6));
                t[3] = (short) (s[2] & 0x3F);
            }
            for (int j = 0; j < 4; j++)
                os.write(Base64.charAt(t[j]));
        }
        return new String(os.toByteArray());
    }

    /**
     * Formats data into a nicely formatted base64 encoded String
     *
     * @param b          An array containing binary data
     * @param lineLength The number of characters per line
     * @param prefix     A string prefixing the characters on each line
     * @param addClose   Whether to add a close parenthesis or not
     * @return A String representing the formatted output
     */
    public static String
    formatString(byte[] b, int lineLength, String prefix, boolean addClose) {
        String s = toString(b);
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < s.length(); i += lineLength) {
            sb.append(prefix);
            if (i + lineLength >= s.length()) {
                sb.append(s.substring(i));
                if (addClose)
                    sb.append(" )");
            } else {
                sb.append(s.substring(i, i + lineLength));
                sb.append("\n");
            }
        }
        return sb.toString();
    }


    /**
     * Convert a base64-encoded String to binary data
     *
     * @param str A String containing the encoded data
     * @return An array containing the binary data, or null if the string is invalid
     */
    public static byte[]
    fromString(String str) {
        ByteArrayOutputStream bs = new ByteArrayOutputStream();
        byte[] raw = str.getBytes();
        for (int i = 0; i < raw.length; i++) {
            if (!Character.isWhitespace((char) raw[i]))
                bs.write(raw[i]);
        }
        byte[] in = bs.toByteArray();
        if (in.length % 4 != 0) {
            return null;
        }

        bs.reset();
        DataOutputStream ds = new DataOutputStream(bs);

        for (int i = 0; i < (in.length + 3) / 4; i++) {
            short[] s = new short[4];
            short[] t = new short[3];

            for (int j = 0; j < 4; j++)
                s[j] = (short) Base64.indexOf(in[i * 4 + j]);

            t[0] = (short) ((s[0] << 2) + (s[1] >> 4));
            if (s[2] == 64) {
                t[1] = t[2] = (short) (-1);
                if ((s[1] & 0xF) != 0)
                    return null;
            } else if (s[3] == 64) {
                t[1] = (short) (((s[1] << 4) + (s[2] >> 2)) & 0xFF);
                t[2] = (short) (-1);
                if ((s[2] & 0x3) != 0)
                    return null;
            } else {
                t[1] = (short) (((s[1] << 4) + (s[2] >> 2)) & 0xFF);
                t[2] = (short) (((s[2] << 6) + s[3]) & 0xFF);
            }

            try {
                for (int j = 0; j < 3; j++)
                    if (t[j] >= 0)
                        ds.writeByte(t[j]);
            } catch (IOException e) {
            }
        }
        return bs.toByteArray();
    }

}
