package org.confucius.commons.util.os.windows;

/**
 * Static methods for translating Base64 encoded strings to byte arrays and vice-versa.
 *
 * @author Josh Bloch
 * @version 1.7, 11/17/05
 * @see java.util.prefs.Preferences
 * @since 1.4
 */
class Base64 {
    /**
     * Translates the specified byte array into a Base64 string as per Preferences.put(byte[]).
     */
    static String byteArrayToBase64(byte[] a) {
        return byteArrayToBase64(a, false);
    }

    /**
     * Translates the specified byte array into an "alternate representation" Base64 string.  This non-standard variant
     * uses an alphabet that does not contain the uppercase alphabetic characters, which makes it suitable for use in
     * situations where case-folding occurs.
     */
    static String byteArrayToAltBase64(byte[] a) {
        return byteArrayToBase64(a, true);
    }

    private static String byteArrayToBase64(byte[] a, boolean alternate) {
        int aLen = a.length;
        int numFullGroups = aLen / 3;
        int numBytesInPartialGroup = aLen - 3 * numFullGroups;
        int resultLen = 4 * ((aLen + 2) / 3);
        StringBuffer result = new StringBuffer(resultLen);
        char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

        // Translate all full groups from byte array elements to Base64
        int inCursor = 0;
        for (int i = 0; i < numFullGroups; i++) {
            int byte0 = a[inCursor++] & 0xff;
            int byte1 = a[inCursor++] & 0xff;
            int byte2 = a[inCursor++] & 0xff;
            result.append(intToAlpha[byte0 >> 2]);
            result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
            result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
            result.append(intToAlpha[byte2 & 0x3f]);
        }

        // Translate partial group if present
        if (numBytesInPartialGroup != 0) {
            int byte0 = a[inCursor++] & 0xff;
            result.append(intToAlpha[byte0 >> 2]);
            if (numBytesInPartialGroup == 1) {
                result.append(intToAlpha[(byte0 << 4) & 0x3f]);
                result.append("==");
            } else {
                // assert numBytesInPartialGroup == 2;
                int byte1 = a[inCursor++] & 0xff;
                result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
                result.append(intToAlpha[(byte1 << 2) & 0x3f]);
                result.append('=');
            }
        }
        // assert inCursor == a.length;
        // assert result.length() == resultLen;
        return result.toString();
    }

    /**
     * This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
     * equivalents as specified in Table 1 of RFC 2045.
     */
    private static final char intToBase64[] = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
    };

    /**
     * This array is a lookup table that translates 6-bit positive integer index values into their "Alternate Base64
     * Alphabet" equivalents. This is NOT the real Base64 Alphabet as per in Table 1 of RFC 2045. This alternate
     * alphabet does not use the capital letters.  It is designed for use in environments where "case folding" occurs.
     */
    private static final char intToAltBase64[] = {
            '!', '"', '#', '$', '%', '&', '\'', '(', ')', ',', '-', '.', ':',
            ';', '<', '>', '@', '[', ']', '^', '`', '_', '{', '|', '}', '~',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '?'
    };

    /**
     * Translates the specified Base64 string (as per Preferences.get(byte[])) into a byte array.
     *
     * @throw IllegalArgumentException if <tt>s</tt> is not a valid Base64 string.
     */
    static byte[] base64ToByteArray(String s) {
        return base64ToByteArray(s, false);
    }

    /**
     * Translates the specified "alternate representation" Base64 string into a byte array.
     *
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if <tt>s</tt> is not a valid alternate
     * representation Base64 string.
     */
    static byte[] altBase64ToByteArray(String s) {
        return base64ToByteArray(s, true);
    }

    private static byte[] base64ToByteArray(String s, boolean alternate) {
        byte[] alphaToInt = (alternate ? altBase64ToInt : base64ToInt);
        int sLen = s.length();
        int numGroups = sLen / 4;
        if (4 * numGroups != sLen)
            throw new IllegalArgumentException(
                    "String length must be a multiple of four.");
        int missingBytesInLastGroup = 0;
        int numFullGroups = numGroups;
        if (sLen != 0) {
            if (s.charAt(sLen - 1) == '=') {
                missingBytesInLastGroup++;
                numFullGroups--;
            }
            if (s.charAt(sLen - 2) == '=')
                missingBytesInLastGroup++;
        }
        byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];

        // Translate all full groups from base64 to byte array elements
        int inCursor = 0, outCursor = 0;
        for (int i = 0; i < numFullGroups; i++) {
            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
            result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
            result[outCursor++] = (byte) ((ch2 << 6) | ch3);
        }

        // Translate partial group, if present
        if (missingBytesInLastGroup != 0) {
            int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
            int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
            result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

            if (missingBytesInLastGroup == 1) {
                int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
                result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
            }
        }
        // assert inCursor == s.length()-missingBytesInLastGroup;
        // assert outCursor == result.length;
        return result;
    }

    /**
     * Translates the specified character, which is assumed to be in the "Base 64 Alphabet" into its equivalent 6-bit
     * positive integer.
     *
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not in the Base64 Alphabet.
     */
    private static int base64toInt(char c, byte[] alphaToInt) {
        int result = alphaToInt[c];
        if (result < 0)
            throw new IllegalArgumentException("Illegal character " + c);
        return result;
    }

    /**
     * This array is a lookup table that translates unicode characters drawn from the "Base64 Alphabet" (as specified in
     * Table 1 of RFC 2045) into their 6-bit positive integer equivalents.  Characters that are not in the Base64
     * alphabet but fall within the bounds of the array are translated to -1.
     */
    private static final byte base64ToInt[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54,
            55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
            5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
            24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34,
            35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
    };

    /**
     * This array is the analogue of base64ToInt, but for the nonstandard variant that avoids the use of uppercase
     * alphabetic characters.
     */
    private static final byte altBase64ToInt[] = {
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1,
            2, 3, 4, 5, 6, 7, 8, -1, 62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57,
            58, 59, 60, 61, 12, 13, 14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, 17, -1, 18, 19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33,
            34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
            51, 22, 23, 24, 25
    };

    public static void main(String args[]) {
        int numRuns = Integer.parseInt(args[0]);
        int numBytes = Integer.parseInt(args[1]);
        java.util.Random rnd = new java.util.Random();
        for (int i = 0; i < numRuns; i++) {
            for (int j = 0; j < numBytes; j++) {
                byte[] arr = new byte[j];
                for (int k = 0; k < j; k++)
                    arr[k] = (byte) rnd.nextInt();

                String s = byteArrayToBase64(arr);
                byte[] b = base64ToByteArray(s);
                if (!java.util.Arrays.equals(arr, b))
                    System.out.println("Dismal failure!");

                s = byteArrayToAltBase64(arr);
                b = altBase64ToByteArray(s);
                if (!java.util.Arrays.equals(arr, b))
                    System.out.println("Alternate dismal failure!");
            }
        }
    }
}

