/*]  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 "config.h"

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

#include <SDL/SDL.h>

#include "debug.hh"
#include "timer.hh"


namespace moof {


void timer::init(const function& function,
				 scalar seconds,
				 mode mode,
				 runloop* runloop)
{
	invalidate();
	ASSERT(runloop && "can't schedule timer without a runloop");

	if ((mode_ = mode) != invalid)
	{
		function_ = function;

		if (mode == absolute)
		{
			absolute_ = seconds;
		}
		else
		{
			absolute_ = seconds - ticks();
			interval_ = seconds;
		}

		runloop->add_timer(this);
		runloop_ = runloop;
	}
}


void timer::invalidate()
{
	if (mode_ != invalid)
	{
		mode_ = invalid;
		absolute_ = SCALAR(0.0);

		runloop_->remove_timer(this);
		runloop_ = 0;
	}
}


void timer::fire(scalar t)
{
	if (function_) function_(*this, t);

	if (is_repeating())
	{
		if (is_equal(absolute_, t, 1.0)) absolute_ += interval_;
		else absolute_ = interval_ + t;
	}
	else invalidate();
}


#if ENABLE_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 set_reference()
{
	struct timespec ts;

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

	return ts.tv_sec;
}

static const time_t reference_ = set_reference();


scalar timer::ticks()
{
	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) * SCALAR(0.000000001);
}

void timer::sleep(scalar seconds, mode mode)
{
	if (mode == absolute) seconds -= ticks();
	if (seconds < SCALAR(0.0)) return;

	struct timespec ts;
	ts.tv_sec = seconds;
	ts.tv_nsec = (seconds - scalar(ts.tv_sec)) * SCALAR(1000000000.0);

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


#else // ! ENABLE_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.  It could end up being just as good anyway.

scalar timer::ticks()
{
	return scalar(SDL_GetTicks()) * SCALAR(0.001);
}

void timer::sleep(scalar seconds, mode mode)
{
	if (mode == absolute) seconds -= ticks();
	if (seconds < SCALAR(0.0)) return;
	SDL_Delay(seconds * SCALAR(1000.0));
}

#endif // ENABLE_CLOCK_GETTIME


} // namespace moof