package org.apache.fory.util;

// Derived from
// https://github.com/yonik/java_util/blob/435ae306d2f2c077d981ab4de5c9ac3c45f92a4b/src/util/hash/MurmurHash3.java.

// yonik/java_util file has no license header

// This implementation is 3.5x faster than Guava's Hashing.murmur3_128.

/**
 * 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 <a href="http://github.com/yonik/java_util">java_util/MurmurHash3</a> for future updates
 * to this file.
 *
 * <p>This java port is faster than guava and consistent cross-language for all seeds, see <a
 * href="https://yonik.com/murmurhash3-for-java/">murmurhash3-for-java</a>
 */
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. */
  @SuppressWarnings("fallthrough")
  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++);
      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 = (int) 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;

      // int used_bits = 32 - shift;  // how many bits of k2 were used in k1.
      // int unused_bits = bits - used_bits; //  (bits-(32-shift)) == bits+shift-32  ==
      // bits-newshift

      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". */
  @SuppressWarnings("fallthrough")
  public static long[] murmurhash3_x64_128(byte[] key, int offset, int len, int seed) {
    // 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;

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