/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2023 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/>.
*/

#ifndef TUNE_H_INCLUDED
#define TUNE_H_INCLUDED

#include <memory>
#include <string>
#include <type_traits>
#include <vector>

namespace Stockfish {

using Range = std::pair<int, int>; // Option's min-max values
using RangeFun = Range (int);

// Default Range function, to calculate Option's min-max values
inline Range default_range(int v) {
  return v > 0 ? Range(0, 2 * v) : Range(2 * v, 0);
}

struct SetRange {
  explicit SetRange(RangeFun f) : fun(f) {}
  SetRange(int min, int max) : fun(nullptr), range(min, max) {}
  Range operator()(int v) const { return fun ? fun(v) : range; }

  RangeFun* fun;
  Range range;
};

#define SetDefaultRange SetRange(default_range)


/// Tune class implements the 'magic' code that makes the setup of a fishtest
/// tuning session as easy as it can be. Mainly you have just to remove const
/// qualifiers from the variables you want to tune and flag them for tuning, so
/// if you have:
///
///   const Score myScore = S(10, 15);
///   const Value myValue[][2] = { { V(100), V(20) }, { V(7), V(78) } };
///
/// If you have a my_post_update() function to run after values have been updated,
/// and a my_range() function to set custom Option's min-max values, then you just
/// remove the 'const' qualifiers and write somewhere below in the file:
///
///   TUNE(SetRange(my_range), myScore, myValue, my_post_update);
///
/// You can also set the range directly, and restore the default at the end
///
///   TUNE(SetRange(-100, 100), myScore, SetDefaultRange);
///
/// In case update function is slow and you have many parameters, you can add:
///
///   UPDATE_ON_LAST();
///
/// And the values update, including post update function call, will be done only
/// once, after the engine receives the last UCI option, that is the one defined
/// and created as the last one, so the GUI should send the options in the same
/// order in which have been defined.

class Tune {

  using PostUpdate = void (); // Post-update function

  Tune() { read_results(); }
  Tune(const Tune&) = delete;
  void operator=(const Tune&) = delete;
  void read_results();

  static Tune& instance() { static Tune t; return t; } // Singleton

  // Use polymorphism to accommodate Entry of different types in the same vector
  struct EntryBase {
    virtual ~EntryBase() = default;
    virtual void init_option() = 0;
    virtual void read_option() = 0;
  };

  template<typename T>
  struct Entry : public EntryBase {

    static_assert(!std::is_const<T>::value, "Parameter cannot be const!");

    static_assert(   std::is_same<T,   int>::value
                  || std::is_same<T, Value>::value
                  || std::is_same<T, Score>::value
                  || std::is_same<T, PostUpdate>::value, "Parameter type not supported!");

    Entry(const std::string& n, T& v, const SetRange& r) : name(n), value(v), range(r) {}
    void operator=(const Entry&) = delete; // Because 'value' is a reference
    void init_option() override;
    void read_option() override;

    std::string name;
    T& value;
    SetRange range;
  };

  // Our facility to fill the container, each Entry corresponds to a parameter
  // to tune. We use variadic templates to deal with an unspecified number of
  // entries, each one of a possible different type.
  static std::string next(std::string& names, bool pop = true);

  int add(const SetRange&, std::string&&) { return 0; }

  template<typename T, typename... Args>
  int add(const SetRange& range, std::string&& names, T& value, Args&&... args) {
    list.push_back(std::unique_ptr<EntryBase>(new Entry<T>(next(names), value, range)));
    return add(range, std::move(names), args...);
  }

  // Template specialization for arrays: recursively handle multi-dimensional arrays
  template<typename T, size_t N, typename... Args>
  int add(const SetRange& range, std::string&& names, T (&value)[N], Args&&... args) {
    for (size_t i = 0; i < N; i++)
        add(range, next(names, i == N - 1) + "[" + std::to_string(i) + "]", value[i]);
    return add(range, std::move(names), args...);
  }

  // Template specialization for SetRange
  template<typename... Args>
  int add(const SetRange&, std::string&& names, SetRange& value, Args&&... args) {
    return add(value, (next(names), std::move(names)), args...);
  }

  std::vector<std::unique_ptr<EntryBase>> list;

public:
  template<typename... Args>
  static int add(const std::string& names, Args&&... args) {
    return instance().add(SetDefaultRange, names.substr(1, names.size() - 2), args...); // Remove trailing parenthesis
  }
  static void init() { for (auto& e : instance().list) e->init_option(); read_options(); } // Deferred, due to UCI::Options access
  static void read_options() { for (auto& e : instance().list) e->read_option(); }
  static bool update_on_last;
};

// Some macro magic :-) we define a dummy int variable that compiler initializes calling Tune::add()
#define STRINGIFY(x) #x
#define UNIQUE2(x, y) x ## y
#define UNIQUE(x, y) UNIQUE2(x, y) // Two indirection levels to expand __LINE__
#define TUNE(...) int UNIQUE(p, __LINE__) = Tune::add(STRINGIFY((__VA_ARGS__)), __VA_ARGS__)

#define UPDATE_ON_LAST() bool UNIQUE(p, __LINE__) = Tune::update_on_last = true

} // namespace Stockfish

#endif // #ifndef TUNE_H_INCLUDED
