/*]  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 {


scalar timer::next_expiration_ = std::numeric_limits<scalar>::max();
hash<unsigned,timer*,hash_function> timer::timers_;


unsigned timer::new_identifier()
{
	static unsigned id = 1;
	return id++;
}


void timer::init(const function& function, scalar seconds, mode mode)
{
	invalidate();

	mode_ = mode;

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

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

		id_ = new_identifier();
		timers_.insert(std::pair<unsigned,timer*>(id_, this));

		if (absolute_ < next_expiration_) next_expiration_ = absolute_;
	}
}


bool timer::is_valid() const
{
	return mode_ != invalid;
}

void timer::invalidate()
{
	if (mode_ != invalid)
	{
		timers_.erase(id_);
		mode_ = invalid;

		if (is_equal(absolute_, next_expiration_))
		{
			next_expiration_ = find_next_expiration();
		}
	}
}


void timer::fire()
{
	scalar t = ticks();

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

	if (is_repeating())
	{
		scalar absolute = absolute_;

		if (is_equal(absolute_, t, 1.0)) absolute_ += interval_;
		else absolute_ = interval_ + t;

		if (is_equal(absolute, next_expiration_))
		{
			next_expiration_ = find_next_expiration();
		}
	}
	else
	{
		invalidate();
	}
}


scalar timer::find_next_expiration()
{
	scalar next_fire = std::numeric_limits<scalar>::max();

	hash<unsigned,timer*,hash_function>::iterator it;
	for (it = timers_.begin(); it != timers_.end(); ++it)
	{
		scalar absolute = (*it).second->absolute_;
		if (absolute < next_fire) next_fire = absolute;
	}

	return next_fire;
}


scalar timer::seconds_remaining() const
{
	return absolute_ - ticks();
}

bool timer::is_expired() const
{
	return seconds_remaining() < 0.0;
}

bool timer::is_repeating() const
{
	return mode_ == repeat;
}


void timer::fire_expired_timers()
{
	fire_expired_timers(ticks());
}

void timer::fire_expired_timers(scalar t)
{
	if (next_expiration_ > t) return;

	hash<unsigned,timer*,hash_function>::iterator it;
	for (it = timers_.begin(); it != timers_.end(); ++it)
	{
		timer* timer = (*it).second;
		if (timer->is_expired()) timer->fire();
	}
}


#if USE_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) / 1000000000.0;
}

void timer::sleep(scalar seconds, mode mode)
{
	struct timespec ts;
	int ret;

	if (mode == absolute) seconds -= ticks();
	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 // ! USE_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::ticks()
{
	Uint32 ms = SDL_GetTicks();
	return scalar(ms / 1000) + scalar(ms % 1000) / 1000.0;
}

void timer::sleep(scalar seconds, mode mode)
{
	if (mode == absolute) seconds -= ticks();
	SDL_Delay(Uint32(clamp(int(seconds * 1000.0), 0, 1000)));
}

#endif // USE_CLOCK_GETTIME


} // namespace moof