// SPDX-FileCopyrightText: 2019-2024 Connor McLaughlin <stenzek@gmail.com>
// SPDX-License-Identifier: (GPL-3.0 OR PolyForm-Strict-1.0.0)

#include "sha1_digest.h"
#include "assert.h"

#include <cstring>

// mostly based on this implementation (public domain): https://gist.github.com/jrabbit/1042021
#define rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

/* blk0() and blk() perform the initial expand. */
/* I got the idea of expanding during the round function from SSLeay */
#define blk0(i) (block->l[i] = (rol(block->l[i], 24) & 0xFF00FF00) | (rol(block->l[i], 8) & 0x00FF00FF))
#define blk(i)                                                                                                         \
  (block->l[i & 15] =                                                                                                  \
     rol(block->l[(i + 13) & 15] ^ block->l[(i + 8) & 15] ^ block->l[(i + 2) & 15] ^ block->l[i & 15], 1))

/* (R0+R1), R2, R3, R4 are the different operations used in SHA1 */
#define R0(v, w, x, y, z, i)                                                                                           \
  z += ((w & (x ^ y)) ^ y) + blk0(i) + 0x5A827999 + rol(v, 5);                                                         \
  w = rol(w, 30);
#define R1(v, w, x, y, z, i)                                                                                           \
  z += ((w & (x ^ y)) ^ y) + blk(i) + 0x5A827999 + rol(v, 5);                                                          \
  w = rol(w, 30);
#define R2(v, w, x, y, z, i)                                                                                           \
  z += (w ^ x ^ y) + blk(i) + 0x6ED9EBA1 + rol(v, 5);                                                                  \
  w = rol(w, 30);
#define R3(v, w, x, y, z, i)                                                                                           \
  z += (((w | x) & y) | (w & x)) + blk(i) + 0x8F1BBCDC + rol(v, 5);                                                    \
  w = rol(w, 30);
#define R4(v, w, x, y, z, i)                                                                                           \
  z += (w ^ x ^ y) + blk(i) + 0xCA62C1D6 + rol(v, 5);                                                                  \
  w = rol(w, 30);

/* Hash a single 512-bit block. This is the core of the algorithm. */

static void SHA1Transform(u32 state[5], const unsigned char buffer[64])
{
  u32 a, b, c, d, e;
  typedef union
  {
    unsigned char c[64];
    u32 l[16];
  } CHAR64LONG16;

  CHAR64LONG16 block[1]; /* use array to appear as a pointer */
  std::memcpy(block, buffer, 64);

  /* Copy context->state[] to working vars */
  a = state[0];
  b = state[1];
  c = state[2];
  d = state[3];
  e = state[4];
  /* 4 rounds of 20 operations each. Loop unrolled. */
  R0(a, b, c, d, e, 0);
  R0(e, a, b, c, d, 1);
  R0(d, e, a, b, c, 2);
  R0(c, d, e, a, b, 3);
  R0(b, c, d, e, a, 4);
  R0(a, b, c, d, e, 5);
  R0(e, a, b, c, d, 6);
  R0(d, e, a, b, c, 7);
  R0(c, d, e, a, b, 8);
  R0(b, c, d, e, a, 9);
  R0(a, b, c, d, e, 10);
  R0(e, a, b, c, d, 11);
  R0(d, e, a, b, c, 12);
  R0(c, d, e, a, b, 13);
  R0(b, c, d, e, a, 14);
  R0(a, b, c, d, e, 15);
  R1(e, a, b, c, d, 16);
  R1(d, e, a, b, c, 17);
  R1(c, d, e, a, b, 18);
  R1(b, c, d, e, a, 19);
  R2(a, b, c, d, e, 20);
  R2(e, a, b, c, d, 21);
  R2(d, e, a, b, c, 22);
  R2(c, d, e, a, b, 23);
  R2(b, c, d, e, a, 24);
  R2(a, b, c, d, e, 25);
  R2(e, a, b, c, d, 26);
  R2(d, e, a, b, c, 27);
  R2(c, d, e, a, b, 28);
  R2(b, c, d, e, a, 29);
  R2(a, b, c, d, e, 30);
  R2(e, a, b, c, d, 31);
  R2(d, e, a, b, c, 32);
  R2(c, d, e, a, b, 33);
  R2(b, c, d, e, a, 34);
  R2(a, b, c, d, e, 35);
  R2(e, a, b, c, d, 36);
  R2(d, e, a, b, c, 37);
  R2(c, d, e, a, b, 38);
  R2(b, c, d, e, a, 39);
  R3(a, b, c, d, e, 40);
  R3(e, a, b, c, d, 41);
  R3(d, e, a, b, c, 42);
  R3(c, d, e, a, b, 43);
  R3(b, c, d, e, a, 44);
  R3(a, b, c, d, e, 45);
  R3(e, a, b, c, d, 46);
  R3(d, e, a, b, c, 47);
  R3(c, d, e, a, b, 48);
  R3(b, c, d, e, a, 49);
  R3(a, b, c, d, e, 50);
  R3(e, a, b, c, d, 51);
  R3(d, e, a, b, c, 52);
  R3(c, d, e, a, b, 53);
  R3(b, c, d, e, a, 54);
  R3(a, b, c, d, e, 55);
  R3(e, a, b, c, d, 56);
  R3(d, e, a, b, c, 57);
  R3(c, d, e, a, b, 58);
  R3(b, c, d, e, a, 59);
  R4(a, b, c, d, e, 60);
  R4(e, a, b, c, d, 61);
  R4(d, e, a, b, c, 62);
  R4(c, d, e, a, b, 63);
  R4(b, c, d, e, a, 64);
  R4(a, b, c, d, e, 65);
  R4(e, a, b, c, d, 66);
  R4(d, e, a, b, c, 67);
  R4(c, d, e, a, b, 68);
  R4(b, c, d, e, a, 69);
  R4(a, b, c, d, e, 70);
  R4(e, a, b, c, d, 71);
  R4(d, e, a, b, c, 72);
  R4(c, d, e, a, b, 73);
  R4(b, c, d, e, a, 74);
  R4(a, b, c, d, e, 75);
  R4(e, a, b, c, d, 76);
  R4(d, e, a, b, c, 77);
  R4(c, d, e, a, b, 78);
  R4(b, c, d, e, a, 79);
  /* Add the working vars back into context.state[] */
  state[0] += a;
  state[1] += b;
  state[2] += c;
  state[3] += d;
  state[4] += e;
}

SHA1Digest::SHA1Digest()
{
  Reset();
}

/* SHA1Init - Initialize new context */

void SHA1Digest::Reset()
{
  /* SHA1 initialization constants */
  state[0] = 0x67452301;
  state[1] = 0xEFCDAB89;
  state[2] = 0x98BADCFE;
  state[3] = 0x10325476;
  state[4] = 0xC3D2E1F0;
  count[0] = count[1] = 0;
}

std::string SHA1Digest::DigestToString(const std::span<u8, DIGEST_SIZE> digest)
{
  std::string ret;
  ret.reserve(DIGEST_SIZE * 2);
  for (u32 i = 0; i < DIGEST_SIZE; i++)
  {
    u8 nibble = digest[i] >> 4;
    if (nibble >= 0xA)
      ret.push_back('A' + (nibble - 0xA));
    else
      ret.push_back('0' + nibble);
    nibble = digest[i] & 0xF;
    if (nibble >= 0xA)
      ret.push_back('A' + (nibble - 0xA));
    else
      ret.push_back('0' + nibble);
  }
  return ret;
}

std::array<u8, SHA1Digest::DIGEST_SIZE> SHA1Digest::GetDigest(const void* data, size_t len)
{
  std::array<u8, SHA1Digest::DIGEST_SIZE> ret;
  SHA1Digest digest;
  digest.Update(data, len);
  digest.Final(ret.data());
  return ret;
}

std::array<u8, SHA1Digest::DIGEST_SIZE> SHA1Digest::GetDigest(std::span<const u8> data)
{
  std::array<u8, SHA1Digest::DIGEST_SIZE> ret;
  SHA1Digest digest;
  digest.Update(data);
  digest.Final(ret.data());
  return ret;
}

/* Run your data through this. */

void SHA1Digest::Update(const void* data, size_t len)
{
  const u8* bdata = static_cast<const u8*>(data);
  Assert(len <= std::numeric_limits<u32>::max());
  const u32 ulen = static_cast<u32>(len);

  u32 i;
  u32 j = count[0];
  if ((count[0] += ulen << 3) < j)
    count[1]++;
  count[1] += (ulen >> 29);
  j = (j >> 3) & 63;
  if ((j + ulen) > 63)
  {
    std::memcpy(&buffer[j], bdata, (i = 64 - j));
    SHA1Transform(state, buffer);
    for (; i + 63 < ulen; i += 64)
    {
      SHA1Transform(state, &bdata[i]);
    }
    j = 0;
  }
  else
  {
    i = 0;
  }
  memcpy(&buffer[j], &bdata[i], len - i);
}

void SHA1Digest::Update(std::span<const u8> data)
{
  Update(data.data(), data.size());
}

/* Add padding and return the message digest. */

void SHA1Digest::Final(u8 digest[DIGEST_SIZE])
{
  u8 finalcount[8];
  u8 c;

  for (u32 i = 0; i < 8; i++)
  {
    finalcount[i] = (u8)((count[(i >= 4 ? 0 : 1)] >> ((3 - (i & 3)) * 8)) & 255); /* Endian independent */
  }

  c = 0200;
  Update(&c, 1);
  while ((count[0] & 504) != 448)
  {
    c = 0000;
    Update(&c, 1);
  }
  Update(finalcount, 8); /* Should cause a SHA1Transform() */
  for (u32 i = 0; i < 20; i++)
  {
    digest[i] = (u8)((state[i >> 2] >> ((3 - (i & 3)) * 8)) & 255);
  }
}
