#include <stdlib.h>
#include <math.h>
#include <SDL/SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>
//#include <mpi.h>

#define PI 3.14159265359

SDL_Surface* screen;
const int screen_width  = 640;
const int screen_height = 480;
const int ball_radius = 20;
int x = 46, y = 17, delta_x = 2, delta_y = 1, energy_loss = 0;

void error(void) {
	// I guess shit went wrong.
	printf("Oh No!/n");
	exit(0);
}

void draw_circle(float x, float y, float r) {
	glBegin(GL_TRIANGLE_FAN);
	glVertex2f(x, y);
	int i;
	for (i=0; i<64; i++) {
		float theta = 2*PI*i/63;
		float nx = x + cosf(theta)*r, ny = y + sinf(theta)*r;
		glVertex2f(nx, ny);
	}
	glEnd();
}

void draw_screen(void) {
	if (SDL_MUSTLOCK(screen) && SDL_LockSurface(screen) < 0)
		return;
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	// Sets the view to be orthographic
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(0, screen_width, screen_height, 0, 0, 1);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();

	glColor4f(1.0, 0.0, 0.0, 1.0);
	/*
	glBegin(GL_QUADS);
	glVertex2f(0.2, 0.2);
	glVertex2f(0.2, 0.5);
	glVertex2f(0.5, 0.5);
	glVertex2f(0.5, 0.2);
	glEnd();
	*/
/*Wall bounce*/
    x=x+delta_x;
    if (x>(screen_width-(2*ball_radius))){ delta_x *= -1;};
    if (x< 0){ delta_x *= -1 ;};

    if (delta_y == 0){delta_y=1;};
    y=y+delta_y;

    if (delta_y>= 0){delta_y = sqrt(2*.2*(y));};
    if (delta_y< 0){delta_y = -1 * sqrt(2*.2*(y));};
//printf("delta y is%d\n",delta_y );
//printf("y is%d\n",y );
    if (y>(screen_height-(2*ball_radius))){ delta_y *= -1;};
    if (y< 0){ delta_y *= -2 ; energy_loss += 1 ;};
    //y += energy_loss;

	draw_circle(x, y, ball_radius);
/*Gravity*/
//delta_y = sqrt(2*.8*y);

	SDL_GL_SwapBuffers();

	if (SDL_MUSTLOCK(screen))
		SDL_UnlockSurface(screen);

	SDL_Flip(screen);
}

int main(int argc, char** argv) {
	//if (argc != 2)
	//	error();
	if (SDL_Init(SDL_INIT_VIDEO) < 0)
		error();
	const SDL_VideoInfo* info = SDL_GetVideoInfo();
	if (info == NULL)
		error();
//	screen_width  = info->current_w;
//	screen_height = info->current_h;
	int videoFlags = 0;
	videoFlags  = SDL_OPENGL;		  /* Enable OpenGL in SDL */
	videoFlags |= SDL_GL_DOUBLEBUFFER; /* Enable double buffering */
	videoFlags |= SDL_HWPALETTE;	   /* Store the palette in hardware */
//	videoFlags |= SDL_RESIZABLE;	   /* Enable window resizing */
//	videoFlags |= SDL_FULLSCREEN;
	// Limits framerate to whatever the vrefresh rate is.
	SDL_GL_SetAttribute(SDL_GL_SWAP_CONTROL, 1);
	screen = SDL_SetVideoMode(screen_width, screen_height, 32, videoFlags);
	if (screen == NULL)
		error();
	glClearColor(0.1, 0.1, 0.1, 1.0); // Set sky color.
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_COLOR_MATERIAL);
/*
	int numcells = atoi(argv[1]);   //set number of processes
	if (numcells == 1)
        error();                    //prevent one process from being used
	if (numcells % 2)
        numcells--;                 // make even if odd
*/

	while (1) {
		draw_screen();
		SDL_Event ev;
		while (SDL_PollEvent(&ev)) {
			if (ev.type == SDL_QUIT || (ev.type == SDL_KEYDOWN && ev.key.keysym.sym == 27)) {
				SDL_Quit();
				return 0;
			}
		}
	}
}