// Copyright 2019 DeepMind Technologies Ltd. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef OPEN_SPIEL_ALGORITHMS_KRIEGSPIEL_ISMCTS_H_
#define OPEN_SPIEL_ALGORITHMS_KRIEGSPIEL_ISMCTS_H_

#include <memory>

#include "open_spiel/algorithms/mcts.h"
#include "open_spiel/abseil-cpp/absl/container/flat_hash_map.h"
#include "open_spiel/algorithms/kriegspiel/infoset.h"

namespace open_spiel {
namespace algorithms {

enum class ISMCTSFinalPolicyType {
  kMaxVisitCount,
  kMaxValue,
};

struct MyTurnNode {
  std::optional<size_t> parent = std::nullopt;
  std::unordered_map<chess::Move, size_t, ChessMoveHash> child_nodes;
};

struct MyMessageNode {
  int visits = 0;
  int available_count = 0;
  double return_sum = 0;

  std::optional<size_t> parent = std::nullopt;
  std::unordered_map<kriegspiel::KriegspielUmpireMessage, size_t, UmpireMessageHash> child_nodes;
};

struct OppTurnNode {
  std::optional<size_t> parent = std::nullopt;
  std::unordered_map<kriegspiel::KriegspielUmpireMessage, size_t, UmpireMessageHash> child_nodes;
};


class MyISMCTSBot : public Bot {
 public:
  MyISMCTSBot(int seed, int move_time,
              StatisticalSamplingInfoset *information_set,
              std::function<double(chess::ChessBoard, chess::Color)> evaluator,
              double uct_c,
              ISMCTSFinalPolicyType final_policy_type);

  void Restart() override;
  void RestartAt(const State& state) override {
    SpielFatalError("Restarting at a specific state not supported");
  }

  Action Step(const State& state) override;
  void ForceAction(const State &state, Action action) override;
  void InformAction(const State &state, Player player_id, Action action) override;

 protected:
  chess::Move RunSearch(std::chrono::time_point<std::chrono::system_clock> step_end);
  void SetCurrentPlayer(const State &state);

  void Reset();

  chess::Move SelectMoveUCB(MyTurnNode* node, const std::vector<chess::Move>& legal_moves);
  chess::Move GetBestMove() const;

  // Run a simulation, returning the player returns.
  virtual void RunSimulation(chess::ChessBoard board);

  std::mt19937 rng_;
  std::function<double(chess::ChessBoard, chess::Color)> evaluator_;
  std::vector<MyTurnNode> my_turn_node_pool_;
  std::vector<MyMessageNode> my_msg_node_pool_;
  std::vector<OppTurnNode> opp_turn_node_pool_;
  int root_node_idx = 0;

  const double uct_c_;
  const ISMCTSFinalPolicyType final_policy_type_;

  int move_time_;
  std::optional<Player> player_ = std::nullopt;
  StatisticalSamplingInfoset *information_set_;
};

}  // namespace algorithms
}  // namespace open_spiel


#endif  // OPEN_SPIEL_ALGORITHMS_KRIEGSPIEL_ISMCTS_H_
