package cn.quantgroup.xyqb.util.encrypt;

/**
 * Base64
 * Created by Rocky on 2016/10/10.
 */
class Base64 {

    /**
     * Chunk size per RFC 2045 section 6.8.
     * <p>
     * <p>The {@value} character limit does not count the trailing CRLF, but counts
     * all other characters, including any equal signs.</p>
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 6.8</a>
     */
    private static final int CHUNK_SIZE = 76;

    /**
     * Chunk separator per RFC 2045 section 2.1.
     *
     * @see <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045 section 2.1</a>
     */
    private static final byte[] CHUNK_SEPARATOR = "\r\n".getBytes();

    /**
     * The base length.
     */
    private static final int BASELENGTH = 255;

    /**
     * Lookup length.
     */
    private static final int LOOKUPLENGTH = 64;

    /**
     * Used to calculate the number of bits in a byte.
     */
    private static final int EIGHTBIT = 8;

    /**
     * Used when encoding something which has fewer than 24 bits.
     */
    private static final int SIXTEENBIT = 16;

    /**
     * Used to determine how many bits data contains.
     */
    private static final int TWENTYFOURBITGROUP = 24;

    /**
     * Used to get the number of Quadruples.
     */
    private static final int FOURBYTE = 4;

    /**
     * Used to test the sign of a byte.
     */
    private static final int SIGN = -128;

    /**
     * Byte used to pad output.
     */
    private static final byte PAD = (byte) '=';
    
    private static final byte LAST_2_BIT = 0x3;
    private static final byte LAST_4_BIT = 0xf;
    private static final char ASCII_A_UPPER = 'A';
    private static final char ASCII_Z_UPPER = 'Z';
    private static final char ASCII_A_LOWER = 'a';
    private static final char ASCII_Z_LOWER = 'z';
    private static final char ASCII_0 = '0';
    private static final char ASCII_9 = '9';
    private static final char A_Z_COUNT = 26;
    private static final char A_Z_LOWER_COUNT = 26;
    private static final char NUMBER_0_9_COUNT = 10;

    // Create arrays to hold the base64 characters and a
    // lookup for base64 chars
    private static byte[] base64Alphabet = new byte[BASELENGTH];
    private static byte[] lookUpBase64Alphabet = new byte[LOOKUPLENGTH];

    // Populating the lookup and character arrays
    static {
        for (int i = 0; i < BASELENGTH; i++) {
            base64Alphabet[i] = (byte) -1;
        }
        for (int i = ASCII_Z_UPPER; i >= ASCII_A_UPPER; i--) {
            base64Alphabet[i] = (byte) (i - ASCII_A_UPPER);
        }
        for (int i = ASCII_Z_LOWER; i >= ASCII_A_LOWER; i--) {
            base64Alphabet[i] = (byte) (i - ASCII_A_LOWER + 26);
        }
        for (int i = ASCII_9; i >= ASCII_0; i--) {
            base64Alphabet[i] = (byte) (i - ASCII_0 + 52);
        }

        base64Alphabet['+'] = 62;
        base64Alphabet['/'] = 63;

        for (int i = 0; i < A_Z_COUNT; i++) {
            lookUpBase64Alphabet[i] = (byte) (ASCII_A_UPPER + i);
        }

        for (int i = A_Z_COUNT, j = 0; i < A_Z_COUNT + A_Z_LOWER_COUNT; i++, j++) {
            lookUpBase64Alphabet[i] = (byte) (ASCII_A_LOWER + j);
        }

        for (int i = A_Z_COUNT + A_Z_LOWER_COUNT, j = 0; i < A_Z_COUNT + A_Z_LOWER_COUNT + NUMBER_0_9_COUNT; i++, j++) {
            lookUpBase64Alphabet[i] = (byte) (ASCII_0 + j);
        }

        lookUpBase64Alphabet[62] = (byte) '+';
        lookUpBase64Alphabet[63] = (byte) '/';
    }

    private static boolean isBase64(byte octect) {
        if (octect == PAD) {
            return true;
        } else if (base64Alphabet[octect] == -1) {
            return false;
        } else {
            return true;
        }
    }

    /**
     * Tests a given byte array to see if it contains
     * only valid characters within the Base64 alphabet.
     *
     * @param arrayOctect byte array to test
     * @return true if all bytes are valid characters in the Base64
     * alphabet or if the byte array is empty; false, otherwise
     */
    public static boolean isArrayByteBase64(byte[] arrayOctect) {

        arrayOctect = discardWhitespace(arrayOctect);

        int length = arrayOctect.length;
        if (length == 0) {
            // shouldn't a 0 length array be valid base64 data?
            // return false;
            return true;
        }
        for (int i = 0; i < length; i++) {
            if (!isBase64(arrayOctect[i])) {
                return false;
            }
        }
        return true;
    }

    /**
     * Encodes binary data using the base64 algorithm but
     * does not chunk the output.
     *
     * @param binaryData binary data to encode
     * @return Base64 characters
     */
    public static byte[] encodeBase64(byte[] binaryData) {
        return encodeBase64(binaryData, false);
    }

    /**
     * Encodes binary data using the base64 algorithm and chunks
     * the encoded output into 76 character blocks
     *
     * @param binaryData binary data to encode
     * @return Base64 characters chunked in 76 character blocks
     */
    public static byte[] encodeBase64Chunked(byte[] binaryData) {
        return encodeBase64(binaryData, true);
    }

    /**
     * Decodes a byte[] containing containing
     * characters in the Base64 alphabet.
     *
     * @param pArray A byte array containing Base64 character data
     * @return a byte array containing binary data
     */
    public static byte[] decode(byte[] pArray) {
        return decodeBase64(pArray);
    }

    /**
     * Encodes binary data using the base64 algorithm, optionally
     * chunking the output into 76 character blocks.
     *
     * @param binaryData Array containing binary data to encode.
     * @param isChunked  if isChunked is true this encoder will chunk
     *                   the base64 output into 76 character blocks
     * @return Base64-encoded data.
     */
    private static byte[] encodeBase64(byte[] binaryData, boolean isChunked) {
        int lengthDataBits = binaryData.length * EIGHTBIT;
        int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
        int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
        byte encodedData[] = null;
        int encodedDataLength = 0;
        int nbrChunks = 0;
        if (fewerThan24bits != 0) {
            //data not divisible by 24 bit
            encodedDataLength = (numberTriplets + 1) * 4;
        } else {
            // 16 or 8 bit
            encodedDataLength = numberTriplets * 4;
        }
        // If the output is to be "chunked" into 76 character sections, for compliance with RFC 2045 MIME, then it is important to allow for extra length to account for the separator(s)
        if (isChunked) {
            nbrChunks = (CHUNK_SEPARATOR.length == 0 ? 0 : (int)Math.ceil((double) encodedDataLength / (double)CHUNK_SIZE));
            encodedDataLength += nbrChunks * CHUNK_SEPARATOR.length;
        }
        encodedData = new byte[encodedDataLength];
        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
        int encodedIndex = 0, dataIndex = 0, chunksSoFar = 0;
        int i = 0;
        int nextSeparatorIndex = CHUNK_SIZE;
        for (i = 0; i < numberTriplets; i++) {
            dataIndex = i * 3;
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            b3 = binaryData[dataIndex + 2];
            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);
            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
            byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex + 1] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex + 2] = lookUpBase64Alphabet[(l << 2) | val3];
            encodedData[encodedIndex + 3] = lookUpBase64Alphabet[b3 & 0x3f];
            encodedIndex += 4;
            // If we are chunking, let's put a chunk separator down.
            if (isChunked) {
                // this assumes that CHUNK_SIZE % 4 == 0
                if (encodedIndex == nextSeparatorIndex) {
                    System.arraycopy(CHUNK_SEPARATOR, 0, encodedData, encodedIndex, CHUNK_SEPARATOR.length);
                    chunksSoFar++;
                    nextSeparatorIndex = (CHUNK_SIZE * (chunksSoFar + 1)) + (chunksSoFar * CHUNK_SEPARATOR.length);
                    encodedIndex += CHUNK_SEPARATOR.length;
                }
            }
        }
        // form integral number of 6-bit groups
        dataIndex = i * 3;
        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & 0x03);
            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex + 1] = lookUpBase64Alphabet[k << 4];
            encodedData[encodedIndex + 2] = PAD;
            encodedData[encodedIndex + 3] = PAD;
        } else if (fewerThan24bits == SIXTEENBIT) {
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);
            byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            encodedData[encodedIndex + 1] = lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex + 2] = lookUpBase64Alphabet[l << 2];
            encodedData[encodedIndex + 3] = PAD;
        }
        if (isChunked) {
            // we also add a separator to the end of the final chunk.
            if (chunksSoFar < nbrChunks) {
                System.arraycopy(CHUNK_SEPARATOR, 0, encodedData, encodedDataLength - CHUNK_SEPARATOR.length, CHUNK_SEPARATOR.length);
            }
        }
        return encodedData;
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param base64Data Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(byte[] base64Data) {
        // RFC 2045 requires that we discard ALL non-Base64 characters
        base64Data = discardNonBase64(base64Data);

        // handle the edge case, so we don't have to worry about it later
        if (base64Data.length == 0) {
            return new byte[0];
        }

        int numberQuadruple = base64Data.length / FOURBYTE;
        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;

        // Throw away anything not in base64Data

        int encodedIndex = 0;
        int dataIndex = 0;
        {
            // this sizes the output array properly - rlw
            int lastData = base64Data.length;
            // ignore the '=' padding
            while (base64Data[lastData - 1] == PAD) {
                if (--lastData == 0) {
                    return new byte[0];
                }
            }
            decodedData = new byte[lastData - numberQuadruple];
        }

        for (int i = 0; i < numberQuadruple; i++) {
            dataIndex = i * 4;
            marker0 = base64Data[dataIndex + 2];
            marker1 = base64Data[dataIndex + 3];

            b1 = base64Alphabet[base64Data[dataIndex]];
            b2 = base64Alphabet[base64Data[dataIndex + 1]];

            if (marker0 != PAD && marker1 != PAD) {
                //No PAD e.g 3cQl
                b3 = base64Alphabet[marker0];
                b4 = base64Alphabet[marker1];

                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                        (byte) (((b2 & LAST_4_BIT) << 4) | ((b3 >> 2) & LAST_4_BIT));
                decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
            } else if (marker0 == PAD) {
                //Two PAD e.g. 3c[Pad][Pad]
                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
            } else if (marker1 == PAD) {
                //One PAD e.g. 3cQ[Pad]
                b3 = base64Alphabet[marker0];

                decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                decodedData[encodedIndex + 1] =
                        (byte) (((b2 & LAST_4_BIT) << 4) | ((b3 >> 2) & LAST_4_BIT));
            }
            encodedIndex += 3;
        }
        return decodedData;
    }

    /**
     * Discards any whitespace from a base-64 encoded block.
     *
     * @param data The base-64 encoded data to discard the whitespace
     *             from.
     * @return The data, less whitespace (see RFC 2045).
     */
    private static byte[] discardWhitespace(byte[] data) {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++) {
            switch (data[i]) {
                case (byte) ' ':
                case (byte) '\n':
                case (byte) '\r':
                case (byte) '\t':
                    break;
                default:
                    groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    /**
     * Discards any characters outside of the base64 alphabet, per
     * the requirements on page 25 of RFC 2045 - "Any characters
     * outside of the base64 alphabet are to be ignored in base64
     * encoded data."
     *
     * @param data The base-64 encoded data to groom
     * @return The data, less non-base64 characters (see RFC 2045).
     */
    private static byte[] discardNonBase64(byte[] data) {
        byte groomedData[] = new byte[data.length];
        int bytesCopied = 0;

        for (int i = 0; i < data.length; i++) {
            if (isBase64(data[i])) {
                groomedData[bytesCopied++] = data[i];
            }
        }

        byte packedData[] = new byte[bytesCopied];

        System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);

        return packedData;
    }

    /**
     * Encodes a byte[] containing binary data, into a byte[] containing
     * characters in the Base64 alphabet.
     *
     * @param pArray a byte array containing binary data
     * @return A byte array containing only Base64 character data
     */
    public static byte[] encode(byte[] pArray) {
        return encodeBase64(pArray, false);
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param encoded string containing Base64 data
     * @return Array containind decoded data.
     */
    public static byte[] decode2(String encoded) {
        if (encoded == null) {
            return null;
        }
        char[] base64Data = encoded.toCharArray();
        // remove white spaces
        int len = removeWhiteSpace(base64Data);
        if (len % FOURBYTE != 0) {
            //should be divisible by four
            return null;
        }
        int numberQuadruple = (len / FOURBYTE);
        if (numberQuadruple == 0) {
            return new byte[0];
        }
        byte decodedData[] = null;
        byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
        char d1 = 0, d2 = 0, d3 = 0, d4 = 0;
        int i = 0;
        int encodedIndex = 0;
        int dataIndex = 0;
        decodedData = new byte[(numberQuadruple) * 3];
        for (; i < numberQuadruple - 1; i++) {
            if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
                    || !isData((d3 = base64Data[dataIndex++]))
                    || !isData((d4 = base64Data[dataIndex++]))) {
                //if found "no data" just return null
                return null;
            }
            b1 = base64Alphabet[d1];
            b2 = base64Alphabet[d2];
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
            decodedData[encodedIndex++] = (byte) (((b2 & LAST_4_BIT) << 4) | ((b3 >> 2) & LAST_4_BIT));
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
        }
        //if found "no data" just return null
        if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
            return null;
        }
        b1 = base64Alphabet[d1];
        b2 = base64Alphabet[d2];
        d3 = base64Data[dataIndex++];
        d4 = base64Data[dataIndex++];
        if (!isData((d3)) || !isData((d4))) {
            //Check if they are PAD characters
            if (isPad(d3) && isPad(d4)) {
                //last 4 bits should be zero
                if ((b2 & LAST_4_BIT) != 0){
                    return null;
                }
                byte[] tmp = new byte[i * 3 + 1];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                return tmp;
            } else if (!isPad(d3) && isPad(d4)) {
                b3 = base64Alphabet[d3];
                //last 2 bits should be zero
                if ((b3 & LAST_2_BIT) != 0){
                    return null;
                }
                byte[] tmp = new byte[i * 3 + 2];
                System.arraycopy(decodedData, 0, tmp, 0, i * 3);
                tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
                tmp[encodedIndex] = (byte) (((b2 & LAST_4_BIT) << 4) | ((b3 >> 2) & LAST_4_BIT));
                return tmp;
            } else {
                return null;
            }
        } else {
            //No PAD e.g 3cQl
            b3 = base64Alphabet[d3];
            b4 = base64Alphabet[d4];
            decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
            decodedData[encodedIndex++] = (byte) (((b2 & LAST_4_BIT) << 4) | ((b3 >> 2) & LAST_4_BIT));
            decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
        }
        return decodedData;
    }

    private static boolean isWhiteSpace(char octect) {
        return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
    }

    private static boolean isData(char octect) {
        return (octect < BASELENGTH && base64Alphabet[octect] != -1);
    }

    private static boolean isPad(char octect) {
        return (octect == PAD);
    }

    /**
     * remove WhiteSpace from MIME containing encoded Base64 data.
     *
     * @param data the byte array of base64 data (with WS)
     * @return the new length
     */
    private static int removeWhiteSpace(char[] data) {
        if (data == null) {
            return 0;
        }

        // count characters that's not whitespace
        int newSize = 0;
        int len = data.length;
        for (int i = 0; i < len; i++) {
            if (!isWhiteSpace(data[i])) {
                data[newSize++] = data[i];
            }
        }
        return newSize;
    }

}
