#pragma once
#ifndef TIMER_H_
#define TIMER_H_

#include<functional>
#include<chrono>
#include<thread>
#include<atomic>
#include<memory>
#include<mutex>
#include<condition_variable>

class Timer
{
public:
	Timer() : _expired(true), _try_to_expire(false)
	{}

	Timer(const Timer& timer)
	{
		_expired = timer._expired.load();
		_try_to_expire = timer._try_to_expire.load();
	}

	~Timer()
	{
		stop();
	}

	void start(int interval, std::function<void()> task)
	{
		// is started, do not start again
		if (_expired == false)
			return;

		// start async timer, launch thread and wait in that thread
		_expired = false;
		std::thread([this, interval, task]() {
			while (!_try_to_expire)
			{
				// sleep every interval and do the task again and again until times up
				std::this_thread::sleep_for(std::chrono::milliseconds(interval));
				task();
			}

			{
				// timer be stopped, update the condition variable expired and wake main thread
				std::lock_guard<std::mutex> locker(_mutex);
				_expired = true;
				_expired_cond.notify_one();
			}
			}).detach();
	}

	void startOnce(int delay, std::function<void()> task)
	{
		std::thread([delay, task]() {
			std::this_thread::sleep_for(std::chrono::milliseconds(delay));
			task();
			}).detach();
	}

	void stop()
	{
		// do not stop again
		if (_expired)
			return;

		if (_try_to_expire)
			return;

		// wait until timer 
		_try_to_expire = true; // change this bool value to make timer while loop stop
		{
			std::unique_lock<std::mutex> locker(_mutex);
			_expired_cond.wait(locker, [this] {return _expired == true; });

			// reset the timer
			if (_expired == true)
				_try_to_expire = false;
		}
	}

private:
	std::atomic<bool> _expired; // timer stopped status
	std::atomic<bool> _try_to_expire; // timer is in stop process
	std::mutex _mutex;
	std::condition_variable _expired_cond;
};

#endif // !_TIMER_H_