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

package org.xbill.DNS.utils;

import java.io.*;

/**
 * Routines for converting between Strings of base32-encoded data and arrays
 * of binary data.  This currently supports the base32 and base32hex alphabets
 * specified in RFC 4648, sections 6 and 7.
 *
 * @author Brian Wellington
 */

public class base32 {

    public static class Alphabet {
        private Alphabet() {
        }

        public static final String BASE32 =
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=";
        public static final String BASE32HEX =
                "0123456789ABCDEFGHIJKLMNOPQRSTUV=";
    }

    ;

    private String alphabet;
    private boolean padding, lowercase;

    /**
     * Creates an object that can be used to do base32 conversions.
     *
     * @param alphabet  Which alphabet should be used
     * @param padding   Whether padding should be used
     * @param lowercase Whether lowercase characters should be used.
     *                  default parameters (The standard base32 alphabet, no padding, uppercase)
     */
    public base32(String alphabet, boolean padding, boolean lowercase) {
        this.alphabet = alphabet;
        this.padding = padding;
        this.lowercase = lowercase;
    }

    static private int
    blockLenToPadding(int blocklen) {
        switch (blocklen) {
            case 1:
                return 6;
            case 2:
                return 4;
            case 3:
                return 3;
            case 4:
                return 1;
            case 5:
                return 0;
            default:
                return -1;
        }
    }

    static private int
    paddingToBlockLen(int padlen) {
        switch (padlen) {
            case 6:
                return 1;
            case 4:
                return 2;
            case 3:
                return 3;
            case 1:
                return 4;
            case 0:
                return 5;
            default:
                return -1;
        }
    }

    /**
     * Convert binary data to a base32-encoded String
     *
     * @param b An array containing binary data
     * @return A String containing the encoded data
     */
    public String
    toString(byte[] b) {
        ByteArrayOutputStream os = new ByteArrayOutputStream();

        for (int i = 0; i < (b.length + 4) / 5; i++) {
            short s[] = new short[5];
            int t[] = new int[8];

            int blocklen = 5;
            for (int j = 0; j < 5; j++) {
                if ((i * 5 + j) < b.length)
                    s[j] = (short) (b[i * 5 + j] & 0xFF);
                else {
                    s[j] = 0;
                    blocklen--;
                }
            }
            int padlen = blockLenToPadding(blocklen);

            // convert the 5 byte block into 8 characters (values 0-31).

            // upper 5 bits from first byte
            t[0] = (byte) ((s[0] >> 3) & 0x1F);
            // lower 3 bits from 1st byte, upper 2 bits from 2nd.
            t[1] = (byte) (((s[0] & 0x07) << 2) | ((s[1] >> 6) & 0x03));
            // bits 5-1 from 2nd.
            t[2] = (byte) ((s[1] >> 1) & 0x1F);
            // lower 1 bit from 2nd, upper 4 from 3rd
            t[3] = (byte) (((s[1] & 0x01) << 4) | ((s[2] >> 4) & 0x0F));
            // lower 4 from 3rd, upper 1 from 4th.
            t[4] = (byte) (((s[2] & 0x0F) << 1) | ((s[3] >> 7) & 0x01));
            // bits 6-2 from 4th
            t[5] = (byte) ((s[3] >> 2) & 0x1F);
            // lower 2 from 4th, upper 3 from 5th;
            t[6] = (byte) (((s[3] & 0x03) << 3) | ((s[4] >> 5) & 0x07));
            // lower 5 from 5th;
            t[7] = (byte) (s[4] & 0x1F);

            // write out the actual characters.
            for (int j = 0; j < t.length - padlen; j++) {
                char c = alphabet.charAt(t[j]);
                if (lowercase)
                    c = Character.toLowerCase(c);
                os.write(c);
            }

            // write out the padding (if any)
            if (padding) {
                for (int j = t.length - padlen; j < t.length; j++)
                    os.write('=');
            }
        }

        return new String(os.toByteArray());
    }

    /**
     * Convert a base32-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 byte[]
    fromString(String str) {
        ByteArrayOutputStream bs = new ByteArrayOutputStream();
        byte[] raw = str.getBytes();
        for (int i = 0; i < raw.length; i++) {
            char c = (char) raw[i];
            if (!Character.isWhitespace(c)) {
                c = Character.toUpperCase(c);
                bs.write((byte) c);
            }
        }

        if (padding) {
            if (bs.size() % 8 != 0)
                return null;
        } else {
            while (bs.size() % 8 != 0)
                bs.write('=');
        }

        byte[] in = bs.toByteArray();

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

        for (int i = 0; i < in.length / 8; i++) {
            short[] s = new short[8];
            int[] t = new int[5];

            int padlen = 8;
            for (int j = 0; j < 8; j++) {
                char c = (char) in[i * 8 + j];
                if (c == '=')
                    break;
                s[j] = (short) alphabet.indexOf(in[i * 8 + j]);
                if (s[j] < 0)
                    return null;
                padlen--;
            }
            int blocklen = paddingToBlockLen(padlen);
            if (blocklen < 0)
                return null;

            // all 5 bits of 1st, high 3 (of 5) of 2nd
            t[0] = (s[0] << 3) | s[1] >> 2;
            // lower 2 of 2nd, all 5 of 3rd, high 1 of 4th
            t[1] = ((s[1] & 0x03) << 6) | (s[2] << 1) | (s[3] >> 4);
            // lower 4 of 4th, high 4 of 5th
            t[2] = ((s[3] & 0x0F) << 4) | ((s[4] >> 1) & 0x0F);
            // lower 1 of 5th, all 5 of 6th, high 2 of 7th
            t[3] = (s[4] << 7) | (s[5] << 2) | (s[6] >> 3);
            // lower 3 of 7th, all of 8th
            t[4] = ((s[6] & 0x07) << 5) | s[7];

            try {
                for (int j = 0; j < blocklen; j++)
                    ds.writeByte((byte) (t[j] & 0xFF));
            } catch (IOException e) {
            }
        }

        return bs.toByteArray();
    }

}
