/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)

  Stockfish is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Code for calculating NNUE evaluation function

#include <iostream>
#include <string>
#include <fstream>
#include <set>

#include "../position.h"
#include "../misc.h"
#include "../uci.h"
#include "../types.h"

#include "evaluate_nnue.h"

namespace Eval::NNUE {

  const uint32_t kpp_board_index[PIECE_NB][COLOR_NB] = {
   // convention: W - us, B - them
   // viewed from other side, W and B are reversed
      { PS_NONE,     PS_NONE     },
      { PS_W_PAWN,   PS_B_PAWN   },
      { PS_W_KNIGHT, PS_B_KNIGHT },
      { PS_W_BISHOP, PS_B_BISHOP },
      { PS_W_ROOK,   PS_B_ROOK   },
      { PS_W_QUEEN,  PS_B_QUEEN  },
      { PS_W_KING,   PS_B_KING   },
      { PS_NONE,     PS_NONE     },
      { PS_NONE,     PS_NONE     },
      { PS_B_PAWN,   PS_W_PAWN   },
      { PS_B_KNIGHT, PS_W_KNIGHT },
      { PS_B_BISHOP, PS_W_BISHOP },
      { PS_B_ROOK,   PS_W_ROOK   },
      { PS_B_QUEEN,  PS_W_QUEEN  },
      { PS_B_KING,   PS_W_KING   },
      { PS_NONE,     PS_NONE     }
  };

  // Input feature converter
  LargePagePtr<FeatureTransformer> feature_transformer;

  // Evaluation function
  AlignedPtr<Network> network;

  // Evaluation function file name
  std::string fileName;

  // Saved evaluation function file name
  std::string savedfileName = "nn.bin";

  // Get a string that represents the structure of the evaluation function
  std::string GetArchitectureString() {
    return "Features=" + FeatureTransformer::GetStructureString() +
      ",Network=" + Network::GetStructureString();
  }

  UseNNUEMode useNNUE;
  std::string eval_file_loaded = "None";

  namespace Detail {

  // Initialize the evaluation function parameters
  template <typename T>
  void Initialize(AlignedPtr<T>& pointer) {

    pointer.reset(reinterpret_cast<T*>(std_aligned_alloc(alignof(T), sizeof(T))));
    std::memset(pointer.get(), 0, sizeof(T));
  }

  template <typename T>
  void Initialize(LargePagePtr<T>& pointer) {

    static_assert(alignof(T) <= 4096, "aligned_large_pages_alloc() may fail for such a big alignment requirement of T");
    pointer.reset(reinterpret_cast<T*>(aligned_large_pages_alloc(sizeof(T))));
    std::memset(pointer.get(), 0, sizeof(T));
  }

  // Read evaluation function parameters
  template <typename T>
  bool ReadParameters(std::istream& stream, T& reference) {

    std::uint32_t header;
    header = read_little_endian<std::uint32_t>(stream);
    if (!stream || header != T::GetHashValue()) return false;
    return reference.ReadParameters(stream);
  }

  // write evaluation function parameters
  template <typename T>
  bool WriteParameters(std::ostream& stream, const AlignedPtr<T>& pointer) {
    constexpr std::uint32_t header = T::GetHashValue();
    stream.write(reinterpret_cast<const char*>(&header), sizeof(header));
    return pointer->WriteParameters(stream);
  }

  template <typename T>
  bool WriteParameters(std::ostream& stream, const LargePagePtr<T>& pointer) {
    constexpr std::uint32_t header = T::GetHashValue();
    stream.write(reinterpret_cast<const char*>(&header), sizeof(header));
    return pointer->WriteParameters(stream);
  }

  }  // namespace Detail

  // Initialize the evaluation function parameters
  void Initialize() {

    Detail::Initialize(feature_transformer);
    Detail::Initialize(network);
  }

  // Read network header
  bool ReadHeader(std::istream& stream, std::uint32_t* hash_value, std::string* architecture)
  {
    std::uint32_t version, size;

    version     = read_little_endian<std::uint32_t>(stream);
    *hash_value = read_little_endian<std::uint32_t>(stream);
    size        = read_little_endian<std::uint32_t>(stream);
    if (!stream || version != kVersion) return false;
    architecture->resize(size);
    stream.read(&(*architecture)[0], size);
    return !stream.fail();
  }

  // write the header
  bool WriteHeader(std::ostream& stream,
    std::uint32_t hash_value, const std::string& architecture) {
    stream.write(reinterpret_cast<const char*>(&kVersion), sizeof(kVersion));
    stream.write(reinterpret_cast<const char*>(&hash_value), sizeof(hash_value));
    const std::uint32_t size = static_cast<std::uint32_t>(architecture.size());
    stream.write(reinterpret_cast<const char*>(&size), sizeof(size));
    stream.write(architecture.data(), size);
    return !stream.fail();
  }

  // Read network parameters
  bool ReadParameters(std::istream& stream) {

    std::uint32_t hash_value;
    std::string architecture;
    if (!ReadHeader(stream, &hash_value, &architecture)) return false;
    if (hash_value != kHashValue) return false;
    if (!Detail::ReadParameters(stream, *feature_transformer)) return false;
    if (!Detail::ReadParameters(stream, *network)) return false;
    return stream && stream.peek() == std::ios::traits_type::eof();
  }
  // write evaluation function parameters
  bool WriteParameters(std::ostream& stream) {
    if (!WriteHeader(stream, kHashValue, GetArchitectureString())) return false;
    if (!Detail::WriteParameters(stream, feature_transformer)) return false;
    if (!Detail::WriteParameters(stream, network)) return false;
    return !stream.fail();
  }
  // Evaluation function. Perform differential calculation.
  Value evaluate(const Position& pos) {

    alignas(kCacheLineSize) TransformedFeatureType
        transformed_features[FeatureTransformer::kBufferSize];
    feature_transformer->Transform(pos, transformed_features);
    alignas(kCacheLineSize) char buffer[Network::kBufferSize];
    const auto output = network->Propagate(transformed_features, buffer);

    return static_cast<Value>(output[0] / FV_SCALE);
  }

  // Load eval, from a file stream or a memory stream
  bool load_eval(std::string name, std::istream& stream) {

    Initialize();

    if (Options["SkipLoadingEval"])
    {
      std::cout << "info string SkipLoadingEval set to true, Net not loaded!" << std::endl;
      return true;
    }
    fileName = name;
    return ReadParameters(stream);
  }

  static UseNNUEMode nnue_mode_from_option(const UCI::Option& mode)
  {
    if (mode == "false")
      return UseNNUEMode::False;
    else if (mode == "true")
      return UseNNUEMode::True;
    else if (mode == "pure")
      return UseNNUEMode::Pure;

    return UseNNUEMode::False;
  }

  void init() {

    useNNUE = nnue_mode_from_option(Options["Use NNUE"]);
    if (useNNUE == UseNNUEMode::False)
        return;

    std::string eval_file = std::string(Options["EvalFile"]);

    #if defined(DEFAULT_NNUE_DIRECTORY)
    #define stringify2(x) #x
    #define stringify(x) stringify2(x)
    std::vector<std::string> dirs = { "" , CommandLine::binaryDirectory , stringify(DEFAULT_NNUE_DIRECTORY) };
    #else
    std::vector<std::string> dirs = { "" , CommandLine::binaryDirectory };
    #endif

    for (std::string directory : dirs)
        if (eval_file_loaded != eval_file)
        {
            std::ifstream stream(directory + eval_file, std::ios::binary);
            if (load_eval(eval_file, stream))
            {
                sync_cout << "info string Loaded eval file " << directory + eval_file << sync_endl;
                eval_file_loaded = eval_file;
            }
            else
            {
                sync_cout << "info string ERROR: failed to load eval file " << directory + eval_file << sync_endl;
            }
        }

    #undef stringify2
    #undef stringify
  }

  /// NNUE::verify() verifies that the last net used was loaded successfully
  void verify() {

    std::string eval_file = std::string(Options["EvalFile"]);

    if (useNNUE != UseNNUEMode::False && eval_file_loaded != eval_file)
    {
        UCI::OptionsMap defaults;
        UCI::init(defaults);

        std::string msg1 = "If the UCI option \"Use NNUE\" is set to true, network evaluation parameters compatible with the engine must be available.";
        std::string msg2 = "The option is set to true, but the network file " + eval_file + " was not loaded successfully.";
        std::string msg3 = "The UCI option EvalFile might need to specify the full path, including the directory name, to the network file.";
        std::string msg4 = "The default net can be downloaded from: https://tests.stockfishchess.org/api/nn/" + std::string(defaults["EvalFile"]);
        std::string msg5 = "The engine will be terminated now.";

        sync_cout << "info string ERROR: " << msg1 << sync_endl;
        sync_cout << "info string ERROR: " << msg2 << sync_endl;
        sync_cout << "info string ERROR: " << msg3 << sync_endl;
        sync_cout << "info string ERROR: " << msg4 << sync_endl;
        sync_cout << "info string ERROR: " << msg5 << sync_endl;

        std::exit(EXIT_FAILURE);
    }

    if (useNNUE != UseNNUEMode::False)
        sync_cout << "info string NNUE evaluation using " << eval_file << " enabled" << sync_endl;
    else
        sync_cout << "info string classical evaluation enabled" << sync_endl;
  }

} // namespace Eval::NNUE