/***************************************************************************
 * Copyright (C) gempa GmbH                                                *
 * All rights reserved.                                                    *
 * Contact: gempa GmbH (seiscomp-dev@gempa.de)                             *
 *                                                                         *
 * GNU Affero General Public License Usage                                 *
 * This file may be used under the terms of the GNU Affero                 *
 * Public License version 3.0 as published by the Free Software Foundation *
 * and appearing in the file LICENSE included in the packaging of this     *
 * file. Please review the following information to ensure the GNU Affero  *
 * Public License version 3.0 requirements will be met:                    *
 * https://www.gnu.org/licenses/agpl-3.0.html.                             *
 *                                                                         *
 * Other Usage                                                             *
 * Alternatively, this file may be used in accordance with the terms and   *
 * conditions contained in a signed written agreement between you and      *
 * gempa GmbH.                                                             *
 ***************************************************************************/


#ifndef SEISCOMP_UTILS_TIMER_H
#define SEISCOMP_UTILS_TIMER_H


#include <seiscomp/core/datetime.h>
#include <seiscomp/core/optional.h>
#include <seiscomp/core/platform/platform.h>
#include <seiscomp/core.h>

#if defined(SC_HAS_TIMER_CREATE)
#include <signal.h>
#include <time.h>
#else
#include <list>
#endif

#include <chrono>
#include <cstdint>
#include <functional>
#include <mutex>
#include <thread>


namespace Seiscomp {
namespace Util {


/** \brief A stopwatch to measure a timespan
  * The stopwatch substracts the timestamps at the time of a
  * call to StopWatch::elapsed and a previous call to Timer::restart
  * or the instantiation of a StopWatch object.
  * \code
  * StopWatch aStopWatch;
  * // do some calculations
  * cout << aStopWatch.elapsed() << " seconds later" << endl;
  * \endcode
  */
class SC_SYSTEM_CORE_API StopWatch {
	public:
		using Clock = std::chrono::high_resolution_clock;

	public:
		//! Constructor
		StopWatch();

		//! Constructor
		StopWatch(bool autorun);

	public:
		//! Restarts the timer, isActive() == true.
		void restart();

		//! Resets the timer, isActive() == false.
		void reset();

		//! Returns whether the timer is active.
		bool isActive() const;

		//! Returns the elapsed time as TimeSpan.
		Seiscomp::Core::TimeSpan elapsed() const;

		//! Returns the elapsed microseconds or 0 if not active.
		uint64_t microseconds() const;

		//! Returns the elapsed nanoseconds or 0 if not active.
		uint64_t nanoseconds() const;

	private:
		OPT(Clock::time_point) _start;
};


/** \brief A timer class that provides repetitive and single-shot timers.
  * This class provides an interface for timers.
  * Usage:
  * \code
  * Timer timer;
  * timer.setTimeout(5);
  * timer.setCallback(myCallbackFunction);
  * timer.start()
  * \endcode
  *
  * Timing: The timer class emits timeouts in one second intervals.
  *         A timer can only set its timeout to a multiple of one second
  *         The timer itself starts immediatly unless another time has
  *         been started already. The the second timer starts at the multiple
  *         of one second + the start time of the first timer
  * Callback: The callback that is called when the timer timeouts runs
  *           within the timer thread and not the one start() has been
  *           called.
  */
class SC_SYSTEM_CORE_API Timer {
	public:
		using Callback = std::function<void ()>;

	public:
		//! C'tor
		Timer(unsigned int timeoutseconds = 0);

		//! D'tor
		~Timer();


	public:
		//! Sets the timeout in seconds
		void setTimeout(unsigned int seconds);

		//! Sets the timeout with possible nanosecond precision.
		//! @return Success flag. Systems that do not support nanosecond
		//!        timers might fail.
		bool setTimeout2(unsigned int seconds, unsigned int nanoseconds);

		//! Sets the callback for the timeout
		void setCallback(const Callback &);

		//! Sets whether the timer is a single-shot timer.
		//! Single-shot timers stop after the first timeout.
		void setSingleShot(bool);

		//! Starts the timer.
		bool start();

		//! Stops the timer.
		bool stop();

		//! Stops the timer if active and waits until it is removed from
		//! the timer list. After this call no callback will be executed.
		bool disable();

		//! Returns the current timer state
		bool isActive() const;


	private:
#if defined(SC_HAS_TIMER_CREATE)
		bool destroy();

		static void handleTimeout(sigval_t self);
#else
		bool deactivate(bool remove);

		static void Loop();
		static bool Update();
#endif

	private:
#if defined(SC_HAS_TIMER_CREATE)
		timer_t          _timerID;
#else
		typedef std::list<Timer*> TimerList;
		static TimerList _timers;
		static std::thread *_thread;
		static std::mutex _mutex;

		bool             _isActive;
		unsigned int     _value;
#endif

		Callback         _callback;
		std::mutex       _callbackMutex;
		unsigned int     _timeout;
#if defined(SC_HAS_TIMER_CREATE)
		unsigned int     _timeoutNs;
#endif
		bool             _singleShot;
};


inline StopWatch::StopWatch() {
	restart();
}

inline void StopWatch::restart() {
	_start = Clock::now();
}

inline uint64_t StopWatch::microseconds() const {
	return _start ? std::chrono::duration_cast<std::chrono::microseconds>(
		Clock::now() - *_start
	).count() : 0;
}

inline uint64_t StopWatch::nanoseconds() const {
	return _start ? std::chrono::duration_cast<std::chrono::nanoseconds>(
		Clock::now() - *_start
	).count() : 0;
}


}
}


#endif