#include "util/crypto_util.hpp"

#include <array>
#include <cstdint>
#include <cstring>
#include <fstream>
#include <iomanip>
#include <random>
#include <sstream>
#include <vector>

namespace lm {
namespace {

constexpr std::uint32_t rotr(std::uint32_t x, std::uint32_t n)
{
  return (x >> n) | (x << (32 - n));
}

void sha256Transform(std::array<std::uint32_t, 8>& state, const std::uint8_t block[64])
{
  static const std::uint32_t 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};

  std::uint32_t w[64];
  for (int i = 0; i < 16; ++i)
  {
    w[i] = (static_cast<std::uint32_t>(block[i * 4]) << 24) |
           (static_cast<std::uint32_t>(block[i * 4 + 1]) << 16) |
           (static_cast<std::uint32_t>(block[i * 4 + 2]) << 8) |
           static_cast<std::uint32_t>(block[i * 4 + 3]);
  }
  for (int i = 16; i < 64; ++i)
  {
    const std::uint32_t s0 = rotr(w[i - 15], 7) ^ rotr(w[i - 15], 18) ^ (w[i - 15] >> 3);
    const std::uint32_t s1 = rotr(w[i - 2], 17) ^ rotr(w[i - 2], 19) ^ (w[i - 2] >> 10);
    w[i] = w[i - 16] + s0 + w[i - 7] + s1;
  }

  std::uint32_t a = state[0];
  std::uint32_t b = state[1];
  std::uint32_t c = state[2];
  std::uint32_t d = state[3];
  std::uint32_t e = state[4];
  std::uint32_t f = state[5];
  std::uint32_t g = state[6];
  std::uint32_t h = state[7];

  for (int i = 0; i < 64; ++i)
  {
    const std::uint32_t S1 = rotr(e, 6) ^ rotr(e, 11) ^ rotr(e, 25);
    const std::uint32_t ch = (e & f) ^ ((~e) & g);
    const std::uint32_t temp1 = h + S1 + ch + k[i] + w[i];
    const std::uint32_t S0 = rotr(a, 2) ^ rotr(a, 13) ^ rotr(a, 22);
    const std::uint32_t maj = (a & b) ^ (a & c) ^ (b & c);
    const std::uint32_t temp2 = S0 + maj;

    h = g;
    g = f;
    f = e;
    e = d + temp1;
    d = c;
    c = b;
    b = a;
    a = temp1 + temp2;
  }

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

}  // namespace

std::string CryptoUtil::sha256Hex(const std::string& data)
{
  std::array<std::uint32_t, 8> state = {0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
                                        0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19};

  const std::uint64_t bit_len = static_cast<std::uint64_t>(data.size()) * 8;
  std::vector<std::uint8_t> msg(data.begin(), data.end());
  msg.push_back(0x80);

  while ((msg.size() % 64) != 56)
    msg.push_back(0x00);

  for (int i = 7; i >= 0; --i)
    msg.push_back(static_cast<std::uint8_t>((bit_len >> (i * 8)) & 0xff));

  for (std::size_t offset = 0; offset < msg.size(); offset += 64)
    sha256Transform(state, msg.data() + offset);

  std::ostringstream oss;
  for (const auto v : state)
    oss << std::hex << std::setw(8) << std::setfill('0') << v;
  return oss.str();
}

std::string CryptoUtil::randomToken(std::size_t bytes)
{
  std::array<unsigned char, 64> buf{};
  const std::size_t n = bytes > buf.size() ? buf.size() : bytes;
  std::ifstream urandom("/dev/urandom", std::ios::binary);
  if (urandom)
    urandom.read(reinterpret_cast<char*>(buf.data()), static_cast<std::streamsize>(n));
  else
  {
    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<int> dist(0, 255);
    for (std::size_t i = 0; i < n; ++i)
      buf[i] = static_cast<unsigned char>(dist(gen));
  }

  std::ostringstream oss;
  for (std::size_t i = 0; i < n; ++i)
    oss << std::hex << std::setw(2) << std::setfill('0') << static_cast<int>(buf[i]);
  return oss.str();
}

std::string CryptoUtil::hashPassword(const std::string& salt, const std::string& password)
{
  return sha256Hex(salt + ":" + password);
}

std::string CryptoUtil::hashPin(const std::string& salt, const std::string& pin)
{
  return sha256Hex(salt + ":pin:" + pin);
}

}  // namespace lm
