#include "matador/utils/uuid.hpp"

#include <random>

namespace matador::utils {
uuid uuid::generate() {
  std::random_device rd;
  std::mt19937_64 gen(rd());
  std::uniform_int_distribution<uint64_t> dist;

  uint64_t high = dist(gen);
  uint64_t low = dist(gen);

  // Set version to 4 (UUID v4)
  high &= 0xFFFFFFFFFFFF0FFFULL;
  high |= 0x0000000000004000ULL;

  // Set variant to 10xx (RFC 4122)
  low &= 0x3FFFFFFFFFFFFFFFULL;
  low |= 0x8000000000000000ULL;

  uuid result;
  result._data[0] = static_cast<uint32_t>(high >> 32);
  result._data[1] = static_cast<uint32_t>(high & 0xFFFFFFFF);
  result._data[2] = static_cast<uint32_t>(low >> 32);
  result._data[3] = static_cast<uint32_t>(low & 0xFFFFFFFF);

  return result;
}

std::string uuid::str() const {
  const char *hex = "0123456789abcdef";
  char out[36]; // UUID string format is 36 characters
  int pos = 0;

  auto write_hex = [&](uint32_t value, int digits) {
    for (int i = digits - 1; i >= 0; --i) {
      out[pos + i] = hex[value & 0xF];
      value >>= 4;
    }
    pos += digits;
  };

  write_hex(_data[0] >> 16, 8);
  out[pos++] = '-';
  write_hex(_data[0] & 0xFFFF, 4);
  out[pos++] = '-';
  write_hex(_data[1] >> 16, 4);
  out[pos++] = '-';
  write_hex(_data[1] & 0xFFFF, 4);
  out[pos++] = '-';
  write_hex(_data[2] >> 16, 4);
  write_hex(_data[2] & 0xFFFF, 4);
  write_hex(_data[3], 4);

  return {out, 36};
}

const uuid::uuid_array &uuid::data() const {
  return _data;
}

bool operator==(const uuid &lhs, const uuid &rhs) {
  return lhs._data == rhs._data;
}

bool operator!=(const uuid &lhs, const uuid &rhs) {
  return !(lhs == rhs);
}

bool operator<(const uuid &lhs, const uuid &rhs) {
  return lhs._data < rhs._data;
}
}

std::size_t std::hash<matador::utils::uuid>::operator()(const matador::utils::uuid &u) const noexcept {
  std::size_t h = 0;
  for (const uint32_t val: u.data()) {
    h ^= std::hash<uint32_t>{}(val) + 0x9e3779b9 + (h << 6) + (h >> 2);
  }
  return h;
}