//! \addtogroup StateMachine
//! \{
//! \file pistatemachine.h
//! \brief
//! \~english State machine.
//! \~russian Машина состояний.
//! \details
//! \~english Main state machine class that manages states and transitions
//! \~russian Основной класс машины состояний, управляющий состояниями и переходами
//! \}
/*
    PIP - Platform Independent Primitives
    State machine
    Ivan Pelipenko peri4ko@yandex.ru, Andrey Bychkov work.a.b@yandex.ru

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

    This program 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 Lesser General Public License for more details.

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

#ifndef pistatemachine_H
#define pistatemachine_H

#include "pistatemachine_state.h"
#include "pistatemachine_transition.h"


//! \ingroup StateMachine
//! \~english Main state machine class
//! \~russian Основной класс машины состояний
class PIP_EXPORT PIStateMachine: public PIStateBase {
public:
	//! \~english Creates state machine with optional name
	//! \~russian Создает машину состояний с опциональным именем
	//! \param n Machine name
	PIStateMachine(const PIString & n = {});

	//! \~english Starts state machine execution
	//! \~russian Запускает выполнение машины состояний
	//! \return true if started successfully
	bool start();

	//! \~english Checks if state machine is running
	//! \~russian Проверяет, запущена ли машина состояний
	//! \return true if running
	bool isRunning() const { return is_running; }

	//! \~english Sets finish callback
	//! \~russian Устанавливает коллбэк завершения
	//! \param f Callback function to call when machine finishes
	void setOnFinish(std::function<void()> f) { on_finish = f; }

	//! \~english Posts event to state machine
	//! \~russian Отправляет событие в машину состояний
	//! \tparam Args Event arguments types
	//! \param event_id Event identifier
	//! \param args Event arguments
	//! \return true if transition was triggered
	template<typename... Args>
	bool postEvent(int event_id, Args... args) {
		if (!is_running) return false;
		if (in_post.exchange(true)) {
			PIMutexLocker ml(nested_mutex);
			nested_posts.enqueue([this, event_id, args...] { postEvent(event_id, args...); });
			// piCout << "queue nested post";
			return false;
		}
		need_finish = false;
		PIScopeExitCall exit_call([this] {
			in_post = false;
			if (need_finish) {
				is_running = false;
				if (on_finish) on_finish();
			} else {
				nested_mutex.lock();
				while (nested_posts.isNotEmpty()) {
					auto np = nested_posts.dequeue();
					nested_mutex.unlock();
					np();
					nested_mutex.lock();
				}
				nested_mutex.unlock();
			}
		});
		PIVector<PIStateBase *> active_states;
		gatherActiveStates(active_states);
		// piCout << "active" << active_states;
		for (auto * s: active_states) {
			for (auto * t: s->transitions) {
				if (t->eventID != event_id) continue;
				if (t->testGuard(args...)) {
					t->trigger();
					return true;
				}
			}
		}
		return false;
	}

private:
	void onFinish() override;

	bool is_running = false, need_finish = false;
	PIQueue<std::function<void()>> nested_posts;
	PIMutex nested_mutex;
	std::atomic_bool in_post = {false};
	std::function<void()> on_finish;
};


#endif