/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
**]  All rights reserved.
*
* vi:ts=4 sw=4 tw=75
*
* Distributable under the terms and conditions of the 2-clause BSD license;
* see the file COPYING for a complete text of the license.
*
**************************************************************************/

#include <cerrno>
#include <ctime>
#include <limits>

#include <SDL/SDL.h>

#include "Log.hh"
#include "Timer.hh"

#if HAVE_CONFIG_H
#include "config.h"
#endif


namespace Mf {


Scalar Timer::gNextFire = std::numeric_limits<Scalar>::max();
std::map<unsigned,Timer*> Timer::gTimers;


unsigned Timer::getNewID()
{
	static unsigned id = 1;
	return id++;
}


void Timer::init(const Function& function, Scalar seconds, Mode mode)
{
	invalidate();

	mMode = mode;

	if (mMode != INVALID)
	{
		mFunction = function;

		if (mode == ACTUAL)
		{
			mAbsolute = seconds;
		}
		else
		{
			mAbsolute = seconds - getTicks();
			mInterval = seconds;
		}

		mId = getNewID();
		gTimers.insert(std::pair<unsigned,Timer*>(mId, this));

		if (mAbsolute < gNextFire) gNextFire = mAbsolute;
	}
}


bool Timer::isValid() const
{
	return mMode != INVALID;
}

void Timer::invalidate()
{
	if (mMode != INVALID)
	{
		gTimers.erase(mId);
		mMode = INVALID;

		if (isEqual(mAbsolute, gNextFire)) gNextFire = findNextFire();
	}
}


void Timer::fire()
{
	Scalar t = getTicks();

	if (mFunction) mFunction(*this, t);

	if (isRepeating())
	{
		Scalar absolute = mAbsolute;

		if (isEqual(mAbsolute, t, 1.0)) mAbsolute += mInterval;
		else mAbsolute = mInterval + t;

		if (isEqual(absolute, gNextFire)) gNextFire = findNextFire();
	}
	else
	{
		invalidate();
	}
}


Scalar Timer::findNextFire()
{
	std::map<unsigned,Timer*>::iterator it;
	Scalar nextFire = std::numeric_limits<Scalar>::max();

	for (it = gTimers.begin(); it != gTimers.end(); ++it)
	{
		Scalar absolute = (*it).second->mAbsolute;
		if (absolute < nextFire) nextFire = absolute;
	}

	return nextFire;
}


Scalar Timer::getSecondsRemaining() const
{
	return mAbsolute - getTicks();
}

bool Timer::isExpired() const
{
	return getSecondsRemaining() < 0.0;
}

bool Timer::isRepeating() const
{
	return mMode == REPEAT;
}


void Timer::fireIfExpired()
{
	fireIfExpired(getTicks());
}

void Timer::fireIfExpired(Scalar t)
{
	std::map<unsigned,Timer*>::iterator it;

	if (gNextFire > t) return;

	for (it = gTimers.begin(); it != gTimers.end(); ++it)
	{
		Timer* timer = (*it).second;
		if (timer->isExpired()) timer->fire();
	}
}


#if HAVE_CLOCK_GETTIME

// Since the monotonic clock will provide us with the time since the
// computer started, the number of seconds since that time could easily
// become so large that it cannot be accurately stored in a float (even
// with as little two days uptime), therefore we need to start from a more
// recent reference (when the program starts).  Of course this isn't much
// of an issue if scalar is a double-precision number.

static time_t setReference_()
{
	struct timespec ts;

	if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
	{
		return 0;
	}

	return ts.tv_sec;
}

static const time_t reference = setReference_();


Scalar Timer::getTicks()
{
	struct timespec ts;

	int result = clock_gettime(CLOCK_MONOTONIC, &ts);
	ASSERT(result == 0 && "cannot access clock");

	return Scalar(ts.tv_sec - reference) +
		   Scalar(ts.tv_nsec) / 1000000000.0;
}

void Timer::sleep(Scalar seconds, Mode mode)
{
	struct timespec ts;
	int ret;

	if (mode == ACTUAL) seconds -= getTicks();
	ts.tv_sec = time_t(seconds);
	ts.tv_nsec = long((seconds - Scalar(ts.tv_sec)) * 1000000000.0);

	do
	{
		ret = nanosleep(&ts, &ts);
	}
	while (ret == -1 && errno == EINTR);
}


#else // ! HAVE_CLOCK_GETTIME


// If we don't have posix timers, we'll have to use a different timing
// method.  SDL only promises centisecond accuracy, but that's better than
// a kick in the pants.

Scalar Timer::getTicks()
{
	Uint32 ms = SDL_GetTicks();
	return Scalar(ms / 1000) + Scalar(ms % 1000) / 1000.0;
}

void Timer::sleep(Scalar seconds, Mode mode)
{
	if (mode == ACTUAL) seconds -= getTicks();
	SDL_Delay(Uint32(cml::clamp(int(seconds * 1000.0), 0, 1000)));
}

#endif // HAVE_CLOCK_GETTIME


} // namespace Mf