/*
 * The MurmurHash3 algorithm was created by Austin Appleby and placed in the public domain. This java port was authored
 * by Yonik Seeley and also placed into the public domain. The author hereby disclaims copyright to this source code.
 * <p> This produces exactly the same hash values as the final C++ version of MurmurHash3 and is thus suitable for
 * producing the same hash values across platforms. <p> The 32 bit x86 version of this hash should be the fastest
 * variant for relatively short keys like ids. murmurhash3_x64_128 is a good choice for longer strings or if you need
 * more than 32 bits of hash. <p> Note - The x86 and x64 versions do _not_ produce the same results, as the algorithms
 * are optimized for their respective platforms. <p> See http://github.com/yonik/java_util for future updates to this
 * file. Special Thanks to Austin Appleby and Yonik Seeley for placing this in the public domain and therefore allowing
 * me to use it!
 */
package bartworks.util;

public final class MurmurHash3 {

    public static int fmix32(int h) {
        h ^= h >>> 16;
        h *= 0x85ebca6b;
        h ^= h >>> 13;
        h *= 0xc2b2ae35;
        h ^= h >>> 16;
        return h;
    }

    public static long fmix64(long k) {
        k ^= k >>> 33;
        k *= 0xff51afd7ed558ccdL;
        k ^= k >>> 33;
        k *= 0xc4ceb9fe1a85ec53L;
        k ^= k >>> 33;
        return k;
    }

    /**
     * Gets a long from a byte buffer in little endian byte order.
     */
    public static long getLongLittleEndian(byte[] buf, int offset) {
        return (long) buf[offset + 7] << 56 // no mask needed
            | (buf[offset + 6] & 0xffL) << 48
            | (buf[offset + 5] & 0xffL) << 40
            | (buf[offset + 4] & 0xffL) << 32
            | (buf[offset + 3] & 0xffL) << 24
            | (buf[offset + 2] & 0xffL) << 16
            | (buf[offset + 1] & 0xffL) << 8
            | buf[offset] & 0xffL; // no shift needed
    }

    /**
     * Returns the MurmurHash3_x86_32 hash.
     */
    public static int murmurhash3_x86_32(byte[] data, int offset, int len, int seed) {

        final int c1 = 0xcc9e2d51;
        final int c2 = 0x1b873593;

        int h1 = seed;
        int roundedEnd = offset + (len & 0xfffffffc); // round down to 4 byte block

        for (int i = offset; i < roundedEnd; i += 4) {
            // little endian load order
            int k1 = data[i] & 0xff | (data[i + 1] & 0xff) << 8 | (data[i + 2] & 0xff) << 16 | data[i + 3] << 24;
            k1 *= c1;
            k1 = k1 << 15 | k1 >>> 17; // ROTL32(k1,15);
            k1 *= c2;

            h1 ^= k1;
            h1 = h1 << 13 | h1 >>> 19; // ROTL32(h1,13);
            h1 = h1 * 5 + 0xe6546b64;
        }

        // tail
        int k1 = 0;

        switch (len & 0x03) {
            case 3:
                k1 = (data[roundedEnd + 2] & 0xff) << 16;
                // fallthrough
            case 2:
                k1 |= (data[roundedEnd + 1] & 0xff) << 8;
                // fallthrough
            case 1:
                k1 |= data[roundedEnd] & 0xff;
                k1 *= c1;
                k1 = k1 << 15 | k1 >>> 17; // ROTL32(k1,15);
                k1 *= c2;
                h1 ^= k1;
        }

        // finalization
        h1 ^= len;

        // fmix(h1);
        h1 ^= h1 >>> 16;
        h1 *= 0x85ebca6b;
        h1 ^= h1 >>> 13;
        h1 *= 0xc2b2ae35;
        h1 ^= h1 >>> 16;

        return h1;
    }

    /**
     * Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String without actually encoding the string to a
     * temporary buffer. This is more than 2x faster than hashing the result of String.getBytes().
     */
    public static int murmurhash3_x86_32(CharSequence data, int offset, int len, int seed) {

        final int c1 = 0xcc9e2d51;
        final int c2 = 0x1b873593;

        int h1 = seed;

        int pos = offset;
        int end = offset + len;
        int k1 = 0;
        int k2 = 0;
        int shift = 0;
        int bits = 0;
        int nBytes = 0; // length in UTF8 bytes

        while (pos < end) {
            int code = data.charAt(pos);
            pos++;
            if (code < 0x80) {
                k2 = code;
                bits = 8;

                /***
                 * // optimized ascii implementation (currently slower!!! code size?) if (shift == 24) { k1 = k1 | (code
                 * << 24);
                 * <p>
                 * k1 *= c1; k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15); k1 *= c2;
                 * <p>
                 * h1 ^= k1; h1 = (h1 << 13) | (h1 >>> 19); // ROTL32(h1,13); h1 = h1*5+0xe6546b64;
                 * <p>
                 * shift = 0; nBytes += 4; k1 = 0; } else { k1 |= code << shift; shift += 8; } continue;
                 ***/
            } else if (code < 0x800) {
                k2 = 0xC0 | code >> 6 | (0x80 | code & 0x3F) << 8;
                bits = 16;
            } else if (code < 0xD800 || code > 0xDFFF || pos >= end) {
                // we check for pos>=end to encode an unpaired surrogate as 3 bytes.
                k2 = 0xE0 | code >> 12 | (0x80 | code >> 6 & 0x3F) << 8 | (0x80 | code & 0x3F) << 16;
                bits = 24;
            } else {
                // surrogate pair
                // int utf32 = pos < end ? (int) data.charAt(pos++) : 0;
                int utf32 = data.charAt(pos++);
                utf32 = (code - 0xD7C0 << 10) + (utf32 & 0x3FF);
                k2 = 0xff & (0xF0 | utf32 >> 18) | (0x80 | utf32 >> 12 & 0x3F) << 8
                    | (0x80 | utf32 >> 6 & 0x3F) << 16
                    | (0x80 | utf32 & 0x3F) << 24;
                bits = 32;
            }

            k1 |= k2 << shift;

            shift += bits;
            if (shift >= 32) {
                // mix after we have a complete word

                k1 *= c1;
                k1 = k1 << 15 | k1 >>> 17; // ROTL32(k1,15);
                k1 *= c2;

                h1 ^= k1;
                h1 = h1 << 13 | h1 >>> 19; // ROTL32(h1,13);
                h1 = h1 * 5 + 0xe6546b64;

                shift -= 32;
                // unfortunately, java won't let you shift 32 bits off, so we need to check for 0
                if (shift != 0) {
                    k1 = k2 >>> bits - shift; // bits used == bits - newshift
                } else {
                    k1 = 0;
                }
                nBytes += 4;
            }
        } // inner

        // handle tail
        if (shift > 0) {
            nBytes += shift >> 3;
            k1 *= c1;
            k1 = k1 << 15 | k1 >>> 17; // ROTL32(k1,15);
            k1 *= c2;
            h1 ^= k1;
        }

        // finalization
        h1 ^= nBytes;

        // fmix(h1);
        h1 ^= h1 >>> 16;
        h1 *= 0x85ebca6b;
        h1 ^= h1 >>> 13;
        h1 *= 0xc2b2ae35;
        h1 ^= h1 >>> 16;

        return h1;
    }

    /**
     * Returns the MurmurHash3_x64_128 hash, placing the result in "out".
     */
    public static void murmurhash3_x64_128(byte[] key, int offset, int len, int seed, LongPair out) {
        // The original algorithm does have a 32 bit unsigned seed.
        // We have to mask to match the behavior of the unsigned types and prevent sign extension.
        long h1 = seed & 0x00000000FFFFFFFFL;
        long h2 = seed & 0x00000000FFFFFFFFL;

        final long c1 = 0x87c37b91114253d5L;
        final long c2 = 0x4cf5ad432745937fL;

        int roundedEnd = offset + (len & 0xFFFFFFF0); // round down to 16 byte block
        for (int i = offset; i < roundedEnd; i += 16) {
            long k1 = getLongLittleEndian(key, i);
            long k2 = getLongLittleEndian(key, i + 8);
            k1 *= c1;
            k1 = Long.rotateLeft(k1, 31);
            k1 *= c2;
            h1 ^= k1;
            h1 = Long.rotateLeft(h1, 27);
            h1 += h2;
            h1 = h1 * 5 + 0x52dce729;
            k2 *= c2;
            k2 = Long.rotateLeft(k2, 33);
            k2 *= c1;
            h2 ^= k2;
            h2 = Long.rotateLeft(h2, 31);
            h2 += h1;
            h2 = h2 * 5 + 0x38495ab5;
        }

        long k1 = 0;
        long k2 = 0;

        switch (len & 15) {
            case 15:
                k2 = (key[roundedEnd + 14] & 0xffL) << 48;
            case 14:
                k2 |= (key[roundedEnd + 13] & 0xffL) << 40;
            case 13:
                k2 |= (key[roundedEnd + 12] & 0xffL) << 32;
            case 12:
                k2 |= (key[roundedEnd + 11] & 0xffL) << 24;
            case 11:
                k2 |= (key[roundedEnd + 10] & 0xffL) << 16;
            case 10:
                k2 |= (key[roundedEnd + 9] & 0xffL) << 8;
            case 9:
                k2 |= key[roundedEnd + 8] & 0xffL;
                k2 *= c2;
                k2 = Long.rotateLeft(k2, 33);
                k2 *= c1;
                h2 ^= k2;
            case 8:
                k1 = (long) key[roundedEnd + 7] << 56;
            case 7:
                k1 |= (key[roundedEnd + 6] & 0xffL) << 48;
            case 6:
                k1 |= (key[roundedEnd + 5] & 0xffL) << 40;
            case 5:
                k1 |= (key[roundedEnd + 4] & 0xffL) << 32;
            case 4:
                k1 |= (key[roundedEnd + 3] & 0xffL) << 24;
            case 3:
                k1 |= (key[roundedEnd + 2] & 0xffL) << 16;
            case 2:
                k1 |= (key[roundedEnd + 1] & 0xffL) << 8;
            case 1:
                k1 |= key[roundedEnd] & 0xffL;
                k1 *= c1;
                k1 = Long.rotateLeft(k1, 31);
                k1 *= c2;
                h1 ^= k1;
        }

        // ----------
        // finalization

        h1 ^= len;
        h2 ^= len;

        h1 += h2;
        h2 += h1;

        h1 = fmix64(h1);
        h2 = fmix64(h2);

        h1 += h2;
        h2 += h1;

        out.val1 = h1;
        out.val2 = h2;
    }

    /**
     * 128 bits of state
     */
    public static final class LongPair {

        public long val1;
        public long val2;
    }
}