#include <SDL2/SDL.h>
#include <SDL2/SDL_error.h>
#include <SDL2/SDL_events.h>
#include <SDL2/SDL_rect.h>
#include <SDL2/SDL_render.h>
#include <SDL2/SDL_video.h>

#include <unistd.h>

#define WIDTH 1920 
#define HEIGHT 1200
#define BALLSIZE 50

SDL_Window *win;	
SDL_Renderer *ren;	

struct {
	int x, y;
	float dx, dy;
} ballPos = {10, 10, 3, 2};

void* cpv(void * v, const char *msg){
	if( v == 0 ){
		fprintf(stderr, "%s -> %s\n",msg, SDL_GetError());
		exit(1);
	}
	return v;
}

int civ(int v, const char *msg){
	if( v != 0 ){
		fprintf(stderr, "%s -> %s\n",msg, SDL_GetError());
		exit(1);
	}
	return v;
}

void ballMove(){
	if(ballPos.x <=0 || ballPos.x >= WIDTH - BALLSIZE){
	   	ballPos.dx = ballPos.dx * -1;
		ballPos.dy = (ballPos.dy / abs(ballPos.dy)) * ((rand() % 5) + 1);
	}
	if(ballPos.y <=0 || ballPos.y >= HEIGHT - BALLSIZE){
	   	ballPos.dy = ballPos.dy * -1;
		ballPos.dx = (ballPos.dx / abs(ballPos.dx)) * ((rand() % 5) + 1);
	}
	ballPos.x = ballPos.x + ballPos.dx;
	ballPos.y = ballPos.y + ballPos.dy;
}

int main()
{
	civ(SDL_Init(SDL_INIT_VIDEO), "can't init SDL");

	win = cpv(SDL_CreateWindow("pong", 0, 0, WIDTH, HEIGHT, SDL_WINDOW_SHOWN), "can't create window");
	ren = cpv(SDL_CreateRenderer(win, -1, SDL_RENDERER_SOFTWARE), "can't create renderer");

	int i = 0;
	SDL_RenderClear(ren);

	SDL_bool should_close = SDL_FALSE;
	SDL_Event e;
	while(!should_close){
		while(SDL_PollEvent(&e)){
			if(e.type == SDL_QUIT){
				should_close = SDL_TRUE;
			}
		}
		/* SDL_SetRenderDrawColor(ren, 0, 0, 0, 255); */
		/* SDL_RenderClear(ren); */

		ballMove();

		SDL_SetRenderDrawColor(ren, (sin((double)i/20) + 1) * 128, (cos((double)i/10) + 1) * 128, (sin((double)i/50) + 1) * 128, 255);
		SDL_Rect ball = {ballPos.x, ballPos.y, BALLSIZE, BALLSIZE};
		SDL_RenderFillRect(ren, &ball);


		SDL_RenderPresent(ren);
		i++;
	}

	return 0;
}