///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2006, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// *       Neither the name of Industrial Light & Magic nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
///////////////////////////////////////////////////////////////////////////

//----------------------------------------------------------------------------
//
//	Timing control for the display thread of the playExr prgram
//
//----------------------------------------------------------------------------

#include "Timer.h"
#include <time.h>

#ifdef _WIN32

    #include <windows.h>

    static int
    gettimeofday (struct timeval *tv, void *tz)
    {
	union
	{
	    ULONGLONG ns100;  // time since 1 Jan 1601 in 100ns units
	    FILETIME ft;
	} now;
    
	GetSystemTimeAsFileTime (&now.ft);
	tv->tv_usec = long ((now.ns100 / 10LL) % 1000000LL);
	tv->tv_sec = long ((now.ns100 - 116444736000000000LL) / 10000000LL);

	return 0;
    } 

#endif


Timer::Timer ():
    playState (RUNNING),
    _spf (1 / 24.0),
    _timingError (0),
    _framesSinceLastFpsFrame (0),
    _actualFrameRate (0)
{
    gettimeofday (&_lastFrameTime, 0);
    _lastFpsFrameTime = _lastFrameTime;
}


void
Timer::waitUntilNextFrameIsDue ()
{
    if (playState != RUNNING)
    {
	//
	// If we are not running, reset all timing state
	// variables and return without waiting.
	//

	gettimeofday (&_lastFrameTime, 0);
	_timingError = 0;
	_lastFpsFrameTime = _lastFrameTime;
	_framesSinceLastFpsFrame = 0;
	return;
    }

    //
    // If less than _spf seconds have passed since the last frame
    // was displayed, sleep until exactly _spf seconds have gone by.
    //

    timeval now;
    gettimeofday (&now, 0);

    float timeSinceLastFrame =  now.tv_sec  - _lastFrameTime.tv_sec +
			       (now.tv_usec - _lastFrameTime.tv_usec) * 1e-6f;

    float timeToSleep = _spf - timeSinceLastFrame - _timingError;

    #ifdef _WIN32

	if (timeToSleep > 0)
	    Sleep (int (timeToSleep * 1000.0f));

    #else

	if (timeToSleep > 0)
	{
	    timespec ts;
	    ts.tv_sec = (time_t) timeToSleep;
	    ts.tv_nsec = (long) ((timeToSleep - ts.tv_sec) * 1e9f);
	    nanosleep (&ts, 0);
	}

    #endif

    //
    // If we slept, it is possible that we woke up a little too early
    // or a little too late.  Keep track of the difference between
    // now and the exact time when we wanted to wake up; next time
    // we'll try sleep that much longer or shorter.  This should
    // keep our average frame rate close to one fame every _spf seconds.
    //

    gettimeofday (&now, 0);

    timeSinceLastFrame =  now.tv_sec  - _lastFrameTime.tv_sec +
		         (now.tv_usec - _lastFrameTime.tv_usec) * 1e-6f;

    _timingError += timeSinceLastFrame - _spf;

    if (_timingError < -2 * _spf)
	_timingError = -2 * _spf;

    if (_timingError >  2 * _spf)
	_timingError =  2 * _spf;

    _lastFrameTime = now;

    //
    // Calculate our actual frame rate, averaged over several frames.
    //

    if (_framesSinceLastFpsFrame >= 24)
    {
	float t =  now.tv_sec  - _lastFpsFrameTime.tv_sec +
		  (now.tv_usec - _lastFpsFrameTime.tv_usec) * 1e-6f;

	if (t > 0)
	    _actualFrameRate = _framesSinceLastFpsFrame / t;

	_framesSinceLastFpsFrame = 0;
    }

    if (_framesSinceLastFpsFrame == 0)
	_lastFpsFrameTime = now;

    _framesSinceLastFpsFrame += 1;
}


void
Timer::setDesiredFrameRate (float fps)
{
    _spf = 1 / fps;
}


float
Timer::actualFrameRate ()
{
    return _actualFrameRate;
}