/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.bookkeeper.common.hash;

import io.netty.buffer.ByteBuf;

/**
 * Murmur3 is successor to Murmur2 fast non-crytographic hash algorithms.
 *
 * Murmur3 32 and 128 bit variants.
 * 32-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#94
 * 128-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#255
 *
 * This is a public domain code with no copyrights.
 * From homepage of MurmurHash (https://code.google.com/p/smhasher/),
 * "All MurmurHash versions are public domain software, and the author disclaims all copyright
 * to their code."
 */
public class Murmur3 {
    // Constants for 32 bit variant
    private static final int C1_32 = 0xcc9e2d51;
    private static final int C2_32 = 0x1b873593;
    private static final int R1_32 = 15;
    private static final int R2_32 = 13;
    private static final int M_32 = 5;
    private static final int N_32 = 0xe6546b64;

    // Constants for 128 bit variant
    private static final long C1 = 0x87c37b91114253d5L;
    private static final long C2 = 0x4cf5ad432745937fL;
    private static final int R1 = 31;
    private static final int R2 = 27;
    private static final int R3 = 33;
    private static final int M = 5;
    private static final int N1 = 0x52dce729;
    private static final int N2 = 0x38495ab5;

    public static final int DEFAULT_SEED = 104729;

    /**
     * Murmur3 32-bit variant.
     *
     * @param data - input byte array
     * @return - hashcode
     */
    public static int hash32(byte[] data) {
        return hash32(data, 0, data.length, DEFAULT_SEED);
    }

    /**
     * Murmur3 32-bit variant.
     *
     * @param data - input byte array
     * @param length - length of array
     * @return - hashcode
     */
    public static int hash32(byte[] data, int length) {
        return hash32(data, 0, length, DEFAULT_SEED);
    }

    /**
     * Murmur3 32-bit variant.
     *
     * @param data   - input byte array
     * @param length - length of array
     * @param seed   - seed. (default 0)
     * @return - hashcode
     */
    public static int hash32(byte[] data, int length, int seed) {
        return hash32(data, 0, length, seed);
    }

    /**
     * Murmur3 32-bit variant.
     *
     * @param data   - input byte array
     * @param offset - offset of data
     * @param length - length of array
     * @param seed   - seed. (default 0)
     * @return - hashcode
     */
    public static int hash32(byte[] data, int offset, int length, int seed) {
        int hash = seed;
        final int nblocks = length >> 2;

        // body
        for (int i = 0; i < nblocks; i++) {
            int i_4 = i << 2;
            int k = (data[offset + i_4] & 0xff)
                | ((data[offset + i_4 + 1] & 0xff) << 8)
                | ((data[offset + i_4 + 2] & 0xff) << 16)
                | ((data[offset + i_4 + 3] & 0xff) << 24);

            // mix functions
            k *= C1_32;
            k = Integer.rotateLeft(k, R1_32);
            k *= C2_32;
            hash ^= k;
            hash = Integer.rotateLeft(hash, R2_32) * M_32 + N_32;
        }

        // tail
        int idx = nblocks << 2;
        int k1 = 0;
        switch (length - idx) {
            case 3:
                k1 ^= data[offset + idx + 2] << 16;
            case 2:
                k1 ^= data[offset + idx + 1] << 8;
            case 1:
                k1 ^= data[offset + idx];

                // mix functions
                k1 *= C1_32;
                k1 = Integer.rotateLeft(k1, R1_32);
                k1 *= C2_32;
                hash ^= k1;
        }

        // finalization
        hash ^= length;
        hash ^= (hash >>> 16);
        hash *= 0x85ebca6b;
        hash ^= (hash >>> 13);
        hash *= 0xc2b2ae35;
        hash ^= (hash >>> 16);

        return hash;
    }

    public static int hash32(ByteBuf data, int offset, int length, int seed) {
        int hash = seed;
        final int nblocks = length >> 2;

        // body
        for (int i = 0; i < nblocks; i++) {
            int i_4 = i << 2;
            int k = (data.getByte(offset + i_4) & 0xff)
                | ((data.getByte(offset + i_4 + 1) & 0xff) << 8)
                | ((data.getByte(offset + i_4 + 2) & 0xff) << 16)
                | ((data.getByte(offset + i_4 + 3) & 0xff) << 24);

            // mix functions
            k *= C1_32;
            k = Integer.rotateLeft(k, R1_32);
            k *= C2_32;
            hash ^= k;
            hash = Integer.rotateLeft(hash, R2_32) * M_32 + N_32;
        }

        // tail
        int idx = nblocks << 2;
        int k1 = 0;
        switch (length - idx) {
            case 3:
                k1 ^= data.getByte(offset + idx + 2) << 16;
            case 2:
                k1 ^= data.getByte(offset + idx + 1) << 8;
            case 1:
                k1 ^= data.getByte(offset + idx);

                // mix functions
                k1 *= C1_32;
                k1 = Integer.rotateLeft(k1, R1_32);
                k1 *= C2_32;
                hash ^= k1;
        }

        // finalization
        hash ^= length;
        hash ^= (hash >>> 16);
        hash *= 0x85ebca6b;
        hash ^= (hash >>> 13);
        hash *= 0xc2b2ae35;
        hash ^= (hash >>> 16);

        return hash;
    }

    /**
     * Murmur3 128-bit variant.
     *
     * @param data - input byte array
     * @return - hashcode (2 longs)
     */
    public static long[] hash128(byte[] data) {
        return hash128(data, 0, data.length, DEFAULT_SEED);
    }

    /**
     * Murmur3 128-bit variant.
     *
     * @param data   - input byte array
     * @param offset - the first element of array
     * @param length - length of array
     * @param seed   - seed. (default is 0)
     * @return - hashcode (2 longs)
     */
    public static long[] hash128(byte[] data, int offset, int length, long seed) {
        long h1 = seed;
        long h2 = seed;
        final int nblocks = length >> 4;

        // body
        for (int i = 0; i < nblocks; i++) {
            final int i16 = i << 4;
            long k1 = ((long) data[offset + i16] & 0xff)
                | (((long) data[offset + i16 + 1] & 0xff) << 8)
                | (((long) data[offset + i16 + 2] & 0xff) << 16)
                | (((long) data[offset + i16 + 3] & 0xff) << 24)
                | (((long) data[offset + i16 + 4] & 0xff) << 32)
                | (((long) data[offset + i16 + 5] & 0xff) << 40)
                | (((long) data[offset + i16 + 6] & 0xff) << 48)
                | (((long) data[offset + i16 + 7] & 0xff) << 56);

            long k2 = ((long) data[offset + i16 + 8] & 0xff)
                | (((long) data[offset + i16 + 9] & 0xff) << 8)
                | (((long) data[offset + i16 + 10] & 0xff) << 16)
                | (((long) data[offset + i16 + 11] & 0xff) << 24)
                | (((long) data[offset + i16 + 12] & 0xff) << 32)
                | (((long) data[offset + i16 + 13] & 0xff) << 40)
                | (((long) data[offset + i16 + 14] & 0xff) << 48)
                | (((long) data[offset + i16 + 15] & 0xff) << 56);

            // mix functions for k1
            k1 *= C1;
            k1 = Long.rotateLeft(k1, R1);
            k1 *= C2;
            h1 ^= k1;
            h1 = Long.rotateLeft(h1, R2);
            h1 += h2;
            h1 = h1 * M + N1;

            // mix functions for k2
            k2 *= C2;
            k2 = Long.rotateLeft(k2, R3);
            k2 *= C1;
            h2 ^= k2;
            h2 = Long.rotateLeft(h2, R1);
            h2 += h1;
            h2 = h2 * M + N2;
        }

        // tail
        long k1 = 0;
        long k2 = 0;
        int tailStart = nblocks << 4;
        switch (length - tailStart) {
            case 15:
                k2 ^= (long) (data[offset + tailStart + 14] & 0xff) << 48;
            case 14:
                k2 ^= (long) (data[offset + tailStart + 13] & 0xff) << 40;
            case 13:
                k2 ^= (long) (data[offset + tailStart + 12] & 0xff) << 32;
            case 12:
                k2 ^= (long) (data[offset + tailStart + 11] & 0xff) << 24;
            case 11:
                k2 ^= (long) (data[offset + tailStart + 10] & 0xff) << 16;
            case 10:
                k2 ^= (long) (data[offset + tailStart + 9] & 0xff) << 8;
            case 9:
                k2 ^= (long) (data[offset + tailStart + 8] & 0xff);
                k2 *= C2;
                k2 = Long.rotateLeft(k2, R3);
                k2 *= C1;
                h2 ^= k2;

            case 8:
                k1 ^= (long) (data[offset + tailStart + 7] & 0xff) << 56;
            case 7:
                k1 ^= (long) (data[offset + tailStart + 6] & 0xff) << 48;
            case 6:
                k1 ^= (long) (data[offset + tailStart + 5] & 0xff) << 40;
            case 5:
                k1 ^= (long) (data[offset + tailStart + 4] & 0xff) << 32;
            case 4:
                k1 ^= (long) (data[offset + tailStart + 3] & 0xff) << 24;
            case 3:
                k1 ^= (long) (data[offset + tailStart + 2] & 0xff) << 16;
            case 2:
                k1 ^= (long) (data[offset + tailStart + 1] & 0xff) << 8;
            case 1:
                k1 ^= (long) (data[offset + tailStart] & 0xff);
                k1 *= C1;
                k1 = Long.rotateLeft(k1, R1);
                k1 *= C2;
                h1 ^= k1;
        }

        // finalization
        h1 ^= length;
        h2 ^= length;

        h1 += h2;
        h2 += h1;

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

        h1 += h2;
        h2 += h1;

        return new long[]{h1, h2};
    }

    /**
     * Murmur3 128-bit variant.
     *
     * @param data   - input byte array
     * @param offset - the first element of array
     * @param length - length of array
     * @param seed   - seed. (default is 0)
     * @return - hashcode (2 longs)
     */
    public static long[] hash128(ByteBuf data, int offset, int length, long seed) {
        long h1 = seed;
        long h2 = seed;
        final int nblocks = length >> 4;

        // body
        for (int i = 0; i < nblocks; i++) {
            final int i16 = i << 4;
            long k1 = ((long) data.getByte(offset + i16) & 0xff)
                | (((long) data.getByte(offset + i16 + 1) & 0xff) << 8)
                | (((long) data.getByte(offset + i16 + 2) & 0xff) << 16)
                | (((long) data.getByte(offset + i16 + 3) & 0xff) << 24)
                | (((long) data.getByte(offset + i16 + 4) & 0xff) << 32)
                | (((long) data.getByte(offset + i16 + 5) & 0xff) << 40)
                | (((long) data.getByte(offset + i16 + 6) & 0xff) << 48)
                | (((long) data.getByte(offset + i16 + 7) & 0xff) << 56);

            long k2 = ((long) data.getByte(offset + i16 + 8) & 0xff)
                | (((long) data.getByte(offset + i16 + 9) & 0xff) << 8)
                | (((long) data.getByte(offset + i16 + 10) & 0xff) << 16)
                | (((long) data.getByte(offset + i16 + 11) & 0xff) << 24)
                | (((long) data.getByte(offset + i16 + 12) & 0xff) << 32)
                | (((long) data.getByte(offset + i16 + 13) & 0xff) << 40)
                | (((long) data.getByte(offset + i16 + 14) & 0xff) << 48)
                | (((long) data.getByte(offset + i16 + 15) & 0xff) << 56);

            // mix functions for k1
            k1 *= C1;
            k1 = Long.rotateLeft(k1, R1);
            k1 *= C2;
            h1 ^= k1;
            h1 = Long.rotateLeft(h1, R2);
            h1 += h2;
            h1 = h1 * M + N1;

            // mix functions for k2
            k2 *= C2;
            k2 = Long.rotateLeft(k2, R3);
            k2 *= C1;
            h2 ^= k2;
            h2 = Long.rotateLeft(h2, R1);
            h2 += h1;
            h2 = h2 * M + N2;
        }

        // tail
        long k1 = 0;
        long k2 = 0;
        int tailStart = nblocks << 4;
        switch (length - tailStart) {
            case 15:
                k2 ^= (long) (data.getByte(offset + tailStart + 14) & 0xff) << 48;
            case 14:
                k2 ^= (long) (data.getByte(offset + tailStart + 13) & 0xff) << 40;
            case 13:
                k2 ^= (long) (data.getByte(offset + tailStart + 12) & 0xff) << 32;
            case 12:
                k2 ^= (long) (data.getByte(offset + tailStart + 11) & 0xff) << 24;
            case 11:
                k2 ^= (long) (data.getByte(offset + tailStart + 10) & 0xff) << 16;
            case 10:
                k2 ^= (long) (data.getByte(offset + tailStart + 9) & 0xff) << 8;
            case 9:
                k2 ^= (long) (data.getByte(offset + tailStart + 8) & 0xff);
                k2 *= C2;
                k2 = Long.rotateLeft(k2, R3);
                k2 *= C1;
                h2 ^= k2;

            case 8:
                k1 ^= (long) (data.getByte(offset + tailStart + 7) & 0xff) << 56;
            case 7:
                k1 ^= (long) (data.getByte(offset + tailStart + 6) & 0xff) << 48;
            case 6:
                k1 ^= (long) (data.getByte(offset + tailStart + 5) & 0xff) << 40;
            case 5:
                k1 ^= (long) (data.getByte(offset + tailStart + 4) & 0xff) << 32;
            case 4:
                k1 ^= (long) (data.getByte(offset + tailStart + 3) & 0xff) << 24;
            case 3:
                k1 ^= (long) (data.getByte(offset + tailStart + 2) & 0xff) << 16;
            case 2:
                k1 ^= (long) (data.getByte(offset + tailStart + 1) & 0xff) << 8;
            case 1:
                k1 ^= (long) (data.getByte(offset + tailStart) & 0xff);
                k1 *= C1;
                k1 = Long.rotateLeft(k1, R1);
                k1 *= C2;
                h1 ^= k1;
        }

        // finalization
        h1 ^= length;
        h2 ^= length;

        h1 += h2;
        h2 += h1;

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

        h1 += h2;
        h2 += h1;

        return new long[]{h1, h2};
    }

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

}
