package house.intelli.core.util;

import static java.util.Objects.*;
import static java.nio.charset.StandardCharsets.*;

/**
 * Standard
 * <a href="http://en.wikipedia.org/wiki/Base64">base64url</a>
 * (<a href="http://en.wikipedia.org/wiki/Base64#RFC_4648">RFC 4648</a>) encoding and decoding.
 * <p>
 * The difference to normal base64 is that base64url replaces '+' by '-' and '/' by '_' in order to make the
 * encoded string usable in URLs and file names without any escaping.
 * <p>
 * This class is an adjusted version of {@code org.apache.commons.codec.binary.Base64}. Thanks to the Apache
 * Software Foundation!
 */
public class Base64Url {

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

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

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

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

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

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

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

    /**
     * Byte used to pad output. We discard this and fill it up as needed. This is not passed to the outside!
     */
    static final byte PAD = 0;

    // 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 = 'Z'; i >= 'A'; i--) {
            base64Alphabet[i] = (byte) (i - 'A');
        }
        for (int i = 'z'; i >= 'a'; i--) {
            base64Alphabet[i] = (byte) (i - 'a' + 26);
        }
        for (int i = '9'; i >= '0'; i--) {
            base64Alphabet[i] = (byte) (i - '0' + 52);
        }

        base64Alphabet['-'] = 62;
        base64Alphabet['_'] = 63;

        for (int i = 0; i <= 25; i++) {
            lookUpBase64Alphabet[i] = (byte) ('A' + i);
        }

        for (int i = 26, j = 0; i <= 51; i++, j++) {
            lookUpBase64Alphabet[i] = (byte) ('a' + j);
        }

        for (int i = 52, j = 0; i <= 61; i++, j++) {
            lookUpBase64Alphabet[i] = (byte) ('0' + j);
        }

        lookUpBase64Alphabet[62] = (byte) '-';
        lookUpBase64Alphabet[63] = (byte) '_';
    }

    private static boolean isBase64(final 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);

        final 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;
    }

    private static byte[] appendPaddingIfNeeded(final byte[] in) {
    	final int remainder = in.length % 4;
    	if (remainder == 0)
    		return in;

    	final int missing = 4 - remainder;
    	final byte[] out = new byte[in.length + missing];
    	System.arraycopy(in, 0, out, 0, in.length);
    	return out;
    }

    private static byte[] discardPaddingIfNeeded(final byte[] in) {
    	if (in[in.length - 1] != PAD)
    		return in;

    	int padQty = 1;
    	while (in[in.length - padQty - 1] == PAD)
    		++padQty;

    	final byte[] out = new byte[in.length - padQty];
    	System.arraycopy(in, 0, out, 0, out.length);
    	return out;
    }

    public static String encodeBase64ToString(final byte[] binaryData) {
    	requireNonNull(binaryData, "binaryData");
    	return new String(encodeBase64(binaryData), US_ASCII);
    }

    /**
     * Encodes binary data using the base64url algorithm.
     *
     * @param binaryData Array containing binary data to encode.
     * @return Base64-encoded data.
     */
    public static byte[] encodeBase64(final byte[] binaryData) {
    	requireNonNull(binaryData, "binaryData");
        final int lengthDataBits = binaryData.length * EIGHTBIT;
        final int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
        final int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
        byte encodedData[] = null;
        int encodedDataLength = 0;

        if (fewerThan24bits != 0) {
            //data not divisible by 24 bit
            encodedDataLength = (numberTriplets + 1) * 4;
        } else {
            // 16 or 8 bit
            encodedDataLength = numberTriplets * 4;
        }

        encodedData = new byte[encodedDataLength];

        byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

        int encodedIndex = 0;
        int dataIndex = 0;
        int i = 0;

        //log.debug("number of triplets = " + numberTriplets);
        for (i = 0; i < numberTriplets; i++) {
            dataIndex = i * 3;
            b1 = binaryData[dataIndex];
            b2 = binaryData[dataIndex + 1];
            b3 = binaryData[dataIndex + 2];

            //log.debug("b1= " + b1 +", b2= " + b2 + ", b3= " + b3);

            l = (byte) (b2 & 0x0f);
            k = (byte) (b1 & 0x03);

            final byte val1 =
                ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            final byte val2 =
                ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
            final byte val3 =
                ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

            encodedData[encodedIndex] = lookUpBase64Alphabet[val1];
            //log.debug( "val2 = " + val2 );
            //log.debug( "k4   = " + (k<<4) );
            //log.debug(  "vak  = " + (val2 | (k<<4)) );
            encodedData[encodedIndex + 1] =
                lookUpBase64Alphabet[val2 | (k << 4)];
            encodedData[encodedIndex + 2] =
                lookUpBase64Alphabet[(l << 2) | val3];
            encodedData[encodedIndex + 3] = lookUpBase64Alphabet[b3 & 0x3f];

            encodedIndex += 4;
        }

        // form integral number of 6-bit groups
        dataIndex = i * 3;

        if (fewerThan24bits == EIGHTBIT) {
            b1 = binaryData[dataIndex];
            k = (byte) (b1 & 0x03);
            //log.debug("b1=" + b1);
            //log.debug("b1<<2 = " + (b1>>2) );
            final 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);

            final byte val1 =
                ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
            final 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;
        }

        return discardPaddingIfNeeded(encodedData);
    }

    public static byte[] decodeBase64FromString(final String base64String) {
    	final byte[] base64Data = requireNonNull(base64String, "base64String").getBytes(US_ASCII);
    	return decodeBase64(base64Data);
    }

    /**
     * Decodes Base64 data into octects
     *
     * @param base64Data Byte array containing Base64 data
     * @return Array containing decoded data.
     */
    public static byte[] decodeBase64(final byte[] base64Data) {
    	requireNonNull(base64Data, "base64Data");
    	// RFC 2045 requires that we discard ALL non-Base64 characters
        return _decodeBase64(appendPaddingIfNeeded(discardNonBase64(base64Data)));
    }
    private static byte[] _decodeBase64(final byte[] base64Data) {
        // handle the edge case, so we don't have to worry about it later
        if (base64Data.length == 0) {
            return new byte[0];
        }

        final 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 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                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 & 0xf) << 4) | ((b3 >> 2) & 0xf));
            }
            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).
     */
    static byte[] discardWhitespace(final byte[] data) {
        final 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];
            }
        }

        final 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).
     */
    static byte[] discardNonBase64(final byte[] data) {
        final 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];
            }
        }

        final byte packedData[] = new byte[bytesCopied];

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

        return packedData;
    }

}