package demo.hashing;

import java.nio.ByteBuffer;

public class CassandraHash {

  private static long getblock(ByteBuffer key, int offset, int index) {
    int i_8 = index << 3;
    return ((long) key.get(offset + i_8 + 0) & 0xff) + (((long) key.get(offset + i_8 + 1) & 0xff) << 8) +
      (((long) key.get(offset + i_8 + 2) & 0xff) << 16) + (((long) key.get(offset + i_8 + 3) & 0xff) << 24) +
      (((long) key.get(offset + i_8 + 4) & 0xff) << 32) + (((long) key.get(offset + i_8 + 5) & 0xff) << 40) +
      (((long) key.get(offset + i_8 + 6) & 0xff) << 48) + (((long) key.get(offset + i_8 + 7) & 0xff) << 56);
  }

  private static long rotl64(long v, int n) {
    return ((v << n) | (v >>> (64 - n)));
  }

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

  //taken from com.twitter.algebird.CassandraMurmurHash
  public static long[] hash3_x64_128(ByteBuffer key, int offset, int length, long seed) {
    final int nblocks = length >> 4; // Process as 128-bit blocks.

    long h1 = seed;
    long h2 = seed;

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

    //----------
    // body

    for (int i = 0; i < nblocks; i++) {
      long k1 = getblock(key, offset, i * 2 + 0);
      long k2 = getblock(key, offset, i * 2 + 1);

      k1 *= c1;
      k1 = rotl64(k1, 31);
      k1 *= c2;
      h1 ^= k1;

      h1 = rotl64(h1, 27);
      h1 += h2;
      h1 = h1 * 5 + 0x52dce729;

      k2 *= c2;
      k2 = rotl64(k2, 33);
      k2 *= c1;
      h2 ^= k2;

      h2 = rotl64(h2, 31);
      h2 += h1;
      h2 = h2 * 5 + 0x38495ab5;
    }

    //----------
    // tail

    // Advance offset to the unprocessed tail of the data.
    offset += nblocks * 16;

    long k1 = 0;
    long k2 = 0;

    switch (length & 15) {
      case 15:
        k2 ^= ((long) key.get(offset + 14)) << 48;
      case 14:
        k2 ^= ((long) key.get(offset + 13)) << 40;
      case 13:
        k2 ^= ((long) key.get(offset + 12)) << 32;
      case 12:
        k2 ^= ((long) key.get(offset + 11)) << 24;
      case 11:
        k2 ^= ((long) key.get(offset + 10)) << 16;
      case 10:
        k2 ^= ((long) key.get(offset + 9)) << 8;
      case 9:
        k2 ^= ((long) key.get(offset + 8)) << 0;
        k2 *= c2;
        k2 = rotl64(k2, 33);
        k2 *= c1;
        h2 ^= k2;

      case 8:
        k1 ^= ((long) key.get(offset + 7)) << 56;
      case 7:
        k1 ^= ((long) key.get(offset + 6)) << 48;
      case 6:
        k1 ^= ((long) key.get(offset + 5)) << 40;
      case 5:
        k1 ^= ((long) key.get(offset + 4)) << 32;
      case 4:
        k1 ^= ((long) key.get(offset + 3)) << 24;
      case 3:
        k1 ^= ((long) key.get(offset + 2)) << 16;
      case 2:
        k1 ^= ((long) key.get(offset + 1)) << 8;
      case 1:
        k1 ^= ((long) key.get(offset));
        k1 *= c1;
        k1 = rotl64(k1, 31);
        k1 *= c2;
        h1 ^= k1;
    }
    ;

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

    h1 ^= length;
    h2 ^= length;

    h1 += h2;
    h2 += h1;

    h1 = fmix(h1);
    h2 = fmix(h2);

    h1 += h2;
    h2 += h1;

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


  //kafka utils
  public static int murmur2(final byte[] data) {
    int length = data.length;
    int seed = 0x9747b28c;
    // 'm' and 'r' are mixing constants generated offline.
    // They're not really 'magic', they just happen to work well.
    final int m = 0x5bd1e995;
    final int r = 24;

    // Initialize the hash to a random value
    int h = seed ^ length;
    int length4 = length / 4;

    for (int i = 0; i < length4; i++) {
      final int i4 = i * 4;
      int k = (data[i4 + 0] & 0xff) + ((data[i4 + 1] & 0xff) << 8) + ((data[i4 + 2] & 0xff) << 16) + ((data[i4 + 3] & 0xff) << 24);
      k *= m;
      k ^= k >>> r;
      k *= m;
      h *= m;
      h ^= k;
    }

    // Handle the last few bytes of the input array
    switch (length % 4) {
      case 3:
        h ^= (data[(length & ~3) + 2] & 0xff) << 16;
      case 2:
        h ^= (data[(length & ~3) + 1] & 0xff) << 8;
      case 1:
        h ^= (data[length & ~3] & 0xff);
        h *= m;
    }

    h ^= h >>> 13;
    h *= m;
    h ^= h >>> 15;

    return h;
  }
}
