/*******************************************************************************

 Copyright (c) 2009, Charles McGarvey
 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.
 
 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 HOLDER 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.

*******************************************************************************/

#include <algorithm>
#include <cstdlib>			// exit
#include <list>
#include <string>

#include <SDL/SDL.h>
#include "fastevents.h"
#include <AL/alut.h>

#include "Dispatcher.hh"
#include "Engine.hh"
#include "Event.hh"
#include "Log.hh"
#include "Random.hh"
#include "Settings.hh"
#include "Timer.hh"
#include "Video.hh"


namespace Mf {


class Engine::Impl
{
public:
	Impl(int argc, char* argv[], const std::string& name,
			const std::string& iconFile, const std::string& configFile,
			Engine& engine) :
		interface(engine),
		timestep(0.01),
		printFps(false)
	{
#if defined(_WIN32) || defined (_WIN64) || defined(__WIN32__)
		if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) != 0)
#else
		if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTTHREAD) != 0)
#endif
		{
			logError("sdl is complaining: %s", SDL_GetError());
			throw Exception(Exception::SDL_ERROR);
		}
		if (FE_Init() != 0)
		{
			logError("fast events error: %s", FE_GetError());
			throw Exception(Exception::SDL_ERROR);
		}
		alutInit(&argc, argv);

		Settings& settings = Settings::getInstance();
		settings.loadFromFile(configFile);
		settings.parseArgs(argc, argv);

		long randomSeed;
		if (settings.get("rngseed", randomSeed)) setSeed(randomSeed);
		else setSeed();

		settings.get("timestep", timestep);

		long maxFps = 40;
		settings.get("maxfps", maxFps);
		drawRate = 1.0 / Scalar(maxFps);

		settings.get("printfps", printFps);

		video = Video::alloc(name, iconFile);
		video->makeActive();
	}

	~Impl()
	{
		// the video object must be destroyed before we can shutdown SDL
		video.reset();

		alutExit();
		FE_Quit();
		SDL_Quit();
	}


	/**
	 * The main loop.  This just calls dispatchEvents(), update(), and draw()
	 * over and over again.  The timing of the update and draw are decoupled.
	 * The actual frame rate is also calculated here.  This function will return
	 * the exit code used to stop the loop.
	 */

	void run()
	{
		Scalar ticksNow = Timer::getTicks();

		Scalar nextStep = ticksNow;
		Scalar nextDraw = ticksNow;
		Scalar nextFpsUpdate = ticksNow + 1.0;

		Scalar totalTime = 0.0;
		Scalar deltaTime = 0.0;
		Scalar accumulator = timestep;

		fps = 0;
		int frameAccum = 0;

		do
		{
			Scalar newTicks = Timer::getTicks();
			deltaTime = newTicks - ticksNow;
			ticksNow = newTicks;

			if (deltaTime >= 0.25) deltaTime = 0.25;
			accumulator += deltaTime;

			Timer::fireIfExpired(ticksNow);

			while (accumulator >= timestep)
			{
				dispatchEvents();
				update(totalTime, timestep);

				totalTime += timestep;
				accumulator -= timestep;

				nextStep += timestep;
			}
			if (ticksNow >= nextStep)
			{
				nextStep = ticksNow + timestep;
			}

			if (ticksNow >= nextDraw)
			{
				frameAccum++;

				if (ticksNow >= nextFpsUpdate) // determine the actual fps
				{
					fps = frameAccum;
					frameAccum = 0;

					nextFpsUpdate += 1.0;
					if (ticksNow >= nextFpsUpdate)
					{
						nextFpsUpdate = ticksNow + 1.0;
					}

					if (printFps)
					{
						logInfo("%d fps", fps);
					}
				}

				draw(accumulator / timestep);
				video->swap();

				nextDraw += drawRate;
				if (ticksNow >= nextDraw)
				{
					// we missed some scheduled draws, so reset the schedule
					nextDraw = ticksNow + drawRate;
				}
			}

			// be a good citizen and give back what you don't need
			Timer::sleep(std::min(std::min(nextStep, nextDraw),
						Timer::getNextFire()), true);
		}
		while (!stack.empty());
	}

	void dispatchEvents()
	{
		SDL_Event event;

		while (FE_PollEvent(&event) == 1)
		{
			switch (event.type)
			{
				case SDL_KEYDOWN:
					if (event.key.keysym.sym == SDLK_ESCAPE &&
							(SDL_GetModState() & KMOD_CTRL) )
					{
						// emergency escape
						exit(0);
					}
					break;

				case SDL_VIDEORESIZE:
					video->resize(event.resize.w, event.resize.h);
					break;
			}

			handleEvent(event);
		}
	}


	void update(Scalar t, Scalar dt)
	{
		for (stackIt = stack.begin(); stackIt != stack.end(); ++stackIt)
		{
			(*stackIt)->update(t, dt);
		}
	}

	void draw(Scalar alpha)
	{
		// FIXME - this will crash if the layer being drawn pops itself
		std::list<LayerP>::reverse_iterator it;
		for (it = stack.rbegin(); it != stack.rend(); ++it)
		{
			(*it)->draw(alpha);
		}
	}

	void handleEvent(const Event& event)
	{
		for (stackIt = stack.begin(); stackIt != stack.end(); ++stackIt)
		{
			if ((*stackIt)->handleEvent(event)) break;
		}
	}


	void pushLayer(LayerP layer)
	{
		ASSERT(layer && "cannot push null layer");
		stack.push_front(layer);
		layer->pushed(interface);
	}

	void popLayer()
	{
		bool fixIt = false;
		if (stack.begin() == stackIt) fixIt = true;

		LayerP popped = stack.front();
		stack.pop_front();
		popped->popped(interface);

		if (fixIt) stackIt = --stack.begin();
	}

	void popLayer(Layer* layer)
	{
		bool fixIt = false;

		std::list<LayerP>::iterator it;
		for (it = stack.begin(); it != stack.end(); ++it)
		{
			if (it == stackIt) fixIt = true;

			if ((*it).get() == layer)
			{
				++it;
				do
				{
					LayerP popped = stack.front();
					stack.pop_front();
					popped->popped(interface);
				}
				while (stack.begin() != it);

				if (fixIt) stackIt = --stack.begin();
				return;
			}
		}
	}

	void clearLayers()
	{
		stack.clear();
		stackIt = stack.begin();
	}


	Engine&				interface;

	VideoP				video;

	std::list<LayerP>			stack;
	std::list<LayerP>::iterator	stackIt;

	Scalar				timestep;
	Scalar				drawRate;

	long				fps;
	bool				printFps;
};


static Engine* instance = 0;

Engine::Engine(int argc, char* argv[], const std::string& name,
		const std::string& iconFile, const std::string& configFile) :
	impl_(new Engine::Impl(argc, argv, name, iconFile, configFile, *this))
{
	instance = this;
}


Engine& Engine::getInstance()
{
	ASSERT(instance && "dereferencing null pointer");
	return *instance;
}


void Engine::run()
{
	return impl_->run();
}

void Engine::setTimestep(Scalar ts)
{
	impl_->timestep = ts;
}

Scalar Engine::getTimestep() const
{
	return impl_->timestep;
}

void Engine::setMaxFrameRate(long maxFps)
{
	impl_->drawRate = 1.0 / Scalar(maxFps);
}

long Engine::getMaxFrameRate() const
{
	return long(1.0 / impl_->drawRate);
}


Video& Engine::getVideo() const
{
	return *impl_->video;
}

long Engine::getFrameRate() const
{
	return impl_->fps;
}


void Engine::pushLayer(LayerP layer)
{
	// pass through
	impl_->pushLayer(layer);
}

void Engine::popLayer()
{
	// pass through
	impl_->popLayer();
}

void Engine::popLayer(Layer* layer)
{
	// pass through
	impl_->popLayer(layer);
}

void Engine::clearLayers()
{
	// pass through
	impl_->clearLayers();
}


} // namespace Mf

/** vim: set ts=4 sw=4 tw=80: *************************************************/