//http://www.youtube.com/user/thecplusplusguy
//The Box2D main program with OpenGL and SDL
#include <iostream>
#include <SDL/SDL.h>
#include <SDL/SDL_image.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <Box2D/Box2D.h>

const int WIDTH=640;
const int HEIGHT=480;
const float M2P=20;
const float P2M=1/M2P;
b2World* world;




b2Body* addRect(int x,int y,int w,int h,bool dyn=true)
{
	b2BodyDef bodydef;
	bodydef.position.Set(x*P2M,y*P2M);
	if(dyn)
		bodydef.type=b2_dynamicBody;
	b2Body* body=world->CreateBody(&bodydef);
	
	b2PolygonShape shape;
	shape.SetAsBox(P2M*w/2,P2M*h/2);
	
	b2FixtureDef fixturedef;
	fixturedef.shape=&shape;
	fixturedef.density=1.0;
	body->CreateFixture(&fixturedef);
	
}

void drawSquare(b2Vec2* points,b2Vec2 center,float angle)
{
	glColor3f(1,1,1);
	glPushMatrix();
		glTranslatef(center.x*M2P,center.y*M2P,0);
		glRotatef(angle*180.0/M_PI,0,0,1);
		glBegin(GL_QUADS);
			for(int i=0;i<4;i++)
				glVertex2f(points[i].x*M2P,points[i].y*M2P);
		glEnd();
	glPopMatrix();
}

void init()
{
	glMatrixMode(GL_PROJECTION);
		glOrtho(0,WIDTH,HEIGHT,0,-1,1);
	glMatrixMode(GL_MODELVIEW);
	glClearColor(0,0,0,1);
	world=new b2World(b2Vec2(0.0,9.81));
	addRect(WIDTH/2,HEIGHT-50,WIDTH,30,false);
}

void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glLoadIdentity();
	b2Body* tmp=world->GetBodyList();
	b2Vec2 points[4];
	while(tmp)
	{
		for(int i=0;i<4;i++)
			points[i]=((b2PolygonShape*)tmp->GetFixtureList()->GetShape())->GetVertex(i);
	
		drawSquare(points,tmp->GetWorldCenter(),tmp->GetAngle());
		tmp=tmp->GetNext();
	}
}

int main(int argc,char** argv)
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_SetVideoMode(640,480,32,SDL_OPENGL);
	Uint32 start;
	SDL_Event event;
	bool running=true;
	init();
	while(running)
	{
		start=SDL_GetTicks();
		while(SDL_PollEvent(&event))
		{
			switch(event.type)
			{
				case SDL_QUIT:
					running=false;
					break;
				case SDL_KEYDOWN:
					switch(event.key.keysym.sym)
					{
						case SDLK_ESCAPE:
							running=false;
							break;
					}
					break;
				case SDL_MOUSEBUTTONDOWN:
					addRect(event.button.x,event.button.y,20,20,true);
					break;
					
			}
		}
		display();
		world->Step(1.0/30.0,8,3);	//update
		SDL_GL_SwapBuffers();
		if(1000.0/30>SDL_GetTicks()-start)
			SDL_Delay(1000.0/30-(SDL_GetTicks()-start));
	}
	SDL_Quit();
}