//! \~\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.
//! \note
//! \~english Thread-safe implementation with nested post handling.
//! \~russian Потокобезопасная реализация с обработкой вложенных постов.
//! \~\sa
//! PIStateBase, PITransitionBase
/*
    PIP - Platform Independent Primitives
	State machine
	Ivan Pelipenko peri4ko@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
//! \~\brief
//! \~english Root object that owns and runs a hierarchical state machine.
//! \~russian Корневой объект, который владеет и запускает иерархическую машину состояний.
class PIP_EXPORT PIStateMachine: public PIStateBase {
public:
	//! \~english Creates a state machine with an optional name.
	//! \~russian Создает машину состояний с необязательным именем.
	PIStateMachine(const PIString & n = {});


	//! \~english Starts the machine from its initial active configuration.
	//! \~russian Запускает машину из ее начальной активной конфигурации.
	bool start();

	//! \~english Returns true while the machine is running.
	//! \~russian Возвращает true, пока машина запущена.
	bool isRunning() const { return is_running; }

	//! \~english Sets a callback invoked when the machine finishes.
	//! \~russian Задает callback-функцию, вызываемую при завершении машины.
	void setOnFinish(std::function<void()> f) { on_finish = std::move(f); }


	//! \~english Posts an event to active states and triggers the first matching transition.
	//! \~russian Посылает событие в активные состояния и запускает первый подходящий переход.
	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
