#include "sha256.h"

#include <assert.h>
#include <string.h>

#define ROTLEFT(a, b) (((a) << (b)) | ((a) >> (32 - (b))))
#define ROTRIGHT(a, b) (((a) >> (b)) | ((a) << (32 - (b))))

#define CH(x, y, z) (((x) & (y)) ^ (~(x) & (z)))
#define MAJ(x, y, z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
#define EP0(x) (ROTRIGHT(x, 2) ^ ROTRIGHT(x, 13) ^ ROTRIGHT(x, 22))
#define EP1(x) (ROTRIGHT(x, 6) ^ ROTRIGHT(x, 11) ^ ROTRIGHT(x, 25))
#define SIG0(x) (ROTRIGHT(x, 7) ^ ROTRIGHT(x, 18) ^ ((x) >> 3))
#define SIG1(x) (ROTRIGHT(x, 17) ^ ROTRIGHT(x, 19) ^ ((x) >> 10))

static u32 kit_sha256_k[64] = {
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b,
  0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01,
  0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7,
  0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
  0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152,
  0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
  0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc,
  0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
  0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819,
  0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08,
  0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f,
  0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

static void kit_sha256_transform(u32 *state, u8 *data) {
  assert(state != NULL);
  assert(data != NULL);

  u32 a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];

  for (i = 0, j = 0; i < 16; ++i, j += 4)
    m[i] = ((u32) data[j] << 24) | ((u32) data[j + 1] << 16) |
           ((u32) data[j + 2] << 8) | ((u32) data[j + 3]);
  for (; i < 64; ++i)
    m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];

  a = state[0];
  b = state[1];
  c = state[2];
  d = state[3];
  e = state[4];
  f = state[5];
  g = state[6];
  h = state[7];

  for (i = 0; i < 64; ++i) {
    t1 = h + EP1(e) + CH(e, f, g) + kit_sha256_k[i] + m[i];
    t2 = EP0(a) + MAJ(a, b, c);
    h  = g;
    g  = f;
    f  = e;
    e  = d + t1;
    d  = c;
    c  = b;
    b  = a;
    a  = t1 + t2;
  }

  state[0] += a;
  state[1] += b;
  state[2] += c;
  state[3] += d;
  state[4] += e;
  state[5] += f;
  state[6] += g;
  state[7] += h;
}

kit_sha256_hash_t kit_sha256(i64 in_size, u8 *in_data) {
  assert(in_size >= 0);
  assert(in_data != NULL);

  u32 state[8] = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
                   0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };

  u8 data[64];

  i64 i;
  i64 datalen = 0;
  u64 bitlen  = 0;

  if (in_data != NULL)
    for (i = 0; i < in_size; ++i) {
      data[datalen] = in_data[i];
      datalen++;

      if (datalen != 64)
        continue;

      kit_sha256_transform(state, data);
      bitlen += 512;
      datalen = 0;
    }

  i = datalen;

  if (datalen < 56) {
    data[i++] = 0x80;
    while (i < 56) data[i++] = 0x00;
  } else {
    data[i++] = 0x80;
    while (i < 64) data[i++] = 0x00;

    kit_sha256_transform(state, data);
    memset(data, 0, 56);
  }

  bitlen += datalen * 8;
  data[63] = bitlen;
  data[62] = bitlen >> 8;
  data[61] = bitlen >> 16;
  data[60] = bitlen >> 24;
  data[59] = bitlen >> 32;
  data[58] = bitlen >> 40;
  data[57] = bitlen >> 48;
  data[56] = bitlen >> 56;

  kit_sha256_transform(state, data);

  kit_sha256_hash_t hash;
  memset(&hash, 0, sizeof hash);

  for (i = 0; i < 4; ++i) {
    hash.v[i]      = (state[0] >> (24 - i * 8)) & 0xff;
    hash.v[i + 4]  = (state[1] >> (24 - i * 8)) & 0xff;
    hash.v[i + 8]  = (state[2] >> (24 - i * 8)) & 0xff;
    hash.v[i + 12] = (state[3] >> (24 - i * 8)) & 0xff;
    hash.v[i + 16] = (state[4] >> (24 - i * 8)) & 0xff;
    hash.v[i + 20] = (state[5] >> (24 - i * 8)) & 0xff;
    hash.v[i + 24] = (state[6] >> (24 - i * 8)) & 0xff;
    hash.v[i + 28] = (state[7] >> (24 - i * 8)) & 0xff;
  }

  return hash;
}

#undef ROTLEFT
#undef ROTRIGHT
#undef CH
#undef MAJ
#undef EP0
#undef EP1
#undef SIG0
#undef SIG1