#pragma once

#ifdef DEBUG_PRINTS_ENABLED
#include <QTextStream>
#include <iostream>
#endif

#include <cinttypes>
#include <cmath>
#include <iomanip>
#include <sstream>
#include <string>
#include <vector>

namespace Algorithms {
struct CRCResult {
  std::string inputBits;
  std::string checksum;
};

struct HammingResult {
  std::string inputBits;
  std::string inputBitsWithControlBits;
  int controlBitsAmount;
  int dataBitsAmount;
  double dataControlRatio;
  bool singleErrorCorrected;
  bool doubleErrorDetected;
};

template <typename T>
inline std::string _checksum_to_string(T checksum) {
  std::stringstream checksumStrStream;

  checksumStrStream << "0x" << std::hex << checksum;

  return checksumStrStream.str();
}

inline char _xor(char a, char b) {
  if (a == b) {
    return '0';
  }
  return '1';
}

template <typename MutIt, typename ConstIt>
inline void _xor_poly(MutIt bits, ConstIt poly, std::size_t length) {
  for (std::size_t i = 0; i < length; i++) {
    *bits = _xor(*bits, *poly);
    bits++;
    poly++;
  }
}

// Bits - data bits in string for, for example "100010101"
// Poly - CRC polynomial in bits form, for example "1011"
// Filler - filler char, either '0' or '1'
CRCResult crc(std::string const& bits, std::string const& poly, char filler) {
  CRCResult result{};
#ifdef DEBUG_PRINTS_ENABLED
  QTextStream out(stdout);

  out << "Input bits: " << QString::fromStdString(bits)
      << ", poly: " << QString::fromStdString(poly) << " filler: " << filler
      << '\n';
#endif

  // Step 1: create working string from data bits, right-padded with filler
  std::string padded_bits = bits + std::string(poly.length() - 1, filler);
#ifdef DEBUG_PRINTS_ENABLED
  out << "Padded input bits: " << QString::fromStdString(padded_bits) << "\n";
  out.flush();
#endif

  // Step 2: loop over the padded bits, and perform XOR with poly
  auto it = padded_bits.begin();
#ifdef DEBUG_PRINTS_ENABLED
  out << QString::fromStdString(padded_bits) << '\n';
#endif
  for (std::size_t i = 0; i < bits.length(); i++) {
    // If the MSB is not 1, continue
    if (*it == '0') {
      it++;
      continue;
    }

#ifdef DEBUG_PRINTS_ENABLED
    out << QString(i, ' ') << QString::fromStdString(poly) << '\n';
    out << QString(padded_bits.length(), '-') << '\n';
    out.flush();
#endif

    // XOR over the poly
    _xor_poly(it, poly.cbegin(), poly.length());
#ifdef DEBUG_PRINTS_ENABLED
    out << QString::fromStdString(padded_bits) << '\n';
#endif
    it++;
  }

#ifdef DEBUG_PRINTS_ENABLED
  out << "Final result: " << QString::fromStdString(padded_bits) << '\n';
  out.flush();
#endif

  // Step 3: take the checksum from data string and convert it to hex string
  std::string const checksum_binary_str = padded_bits.substr(bits.length());
  auto checksum_value = std::stoul(checksum_binary_str, nullptr, 2);

  result.inputBits = bits;
  result.checksum = _checksum_to_string(checksum_value);

  return result;
}

}  // namespace Algorithms