/*
 *	happy.c
 *	written by Holmes Futrell
 *	use however you want
 */

#include "SDL.h"
#include "common.h"

#define NUM_HAPPY_FACES 100					/* number of faces to draw */
#define MILLESECONDS_PER_FRAME 16			/* about 60 frames per second */
#define HAPPY_FACE_SIZE 32					/* width and height of happyface (pixels) */

static SDL_TextureID texture_id = 0;		/* reference to texture holding happyface */

static struct {
	float x, y;								/* position of happyface */
	float xvel, yvel;						/* velocity of happyface */
} faces[NUM_HAPPY_FACES];

/*
	Sets initial positions and velocities of happyfaces
	units of velocity are pixels per millesecond
*/
void initializeHappyFaces() {
	int i;
	for (i=0; i<NUM_HAPPY_FACES; i++) {
		faces[i].x		= randomFloat(0.0f, SCREEN_WIDTH  - HAPPY_FACE_SIZE);
		faces[i].y		= randomFloat(0.0f, SCREEN_HEIGHT - HAPPY_FACE_SIZE);
		faces[i].xvel	= randomFloat(-0.1f, 0.1f);
		faces[i].yvel	= randomFloat(-0.1f, 0.1f);
	}
}

void render(void) {
	
	int i;
	SDL_Rect srcRect;	
	SDL_Rect dstRect;
	
	/* setup boundaries for happyface bouncing */
	Uint16 maxx = SCREEN_WIDTH - HAPPY_FACE_SIZE;
	Uint16 maxy = SCREEN_HEIGHT - HAPPY_FACE_SIZE;
	Uint16 minx = 0;
	Uint16 miny = 0;
		
	/* setup rects for drawing */
	srcRect.x = 0;
	srcRect.y = 0;
	srcRect.w = HAPPY_FACE_SIZE;
	srcRect.h = HAPPY_FACE_SIZE;
	dstRect.w = HAPPY_FACE_SIZE;
	dstRect.h = HAPPY_FACE_SIZE;
	
	/* fill background in with black */
	SDL_RenderFill(0, 0, 0, 255, NULL);
	
	/*
	   loop through all the happy faces:
	   - update position
	   - update velocity (if boundary is hit)
	   - draw
	*/
	for (i=0; i<NUM_HAPPY_FACES; i++) {
		faces[i].x += faces[i].xvel * MILLESECONDS_PER_FRAME;
		faces[i].y += faces[i].yvel * MILLESECONDS_PER_FRAME;
		if (faces[i].x > maxx) {
			faces[i].x = maxx;
			faces[i].xvel = -faces[i].xvel;
		}
		else if (faces[i].y > maxy) {
			faces[i].y = maxy;
			faces[i].yvel = -faces[i].yvel;
		}
		if (faces[i].x < minx) {
			faces[i].x = minx;
			faces[i].xvel = -faces[i].xvel;
		}
		else if (faces[i].y < miny) {
			faces[i].y = miny;
			faces[i].yvel = -faces[i].yvel;
		}
		dstRect.x = faces[i].x;
		dstRect.y = faces[i].y;
		SDL_RenderCopy(texture_id, &srcRect, &dstRect);
	}
	/* update screen */
	SDL_RenderPresent();
	
}

/*
	loads the happyface graphic into a texture
*/
void initializeTexture() {
	SDL_Surface *bmp_surface;
	SDL_Surface *bmp_surface_rgba;
	int format = SDL_PIXELFORMAT_ABGR8888; /* desired texture format */
	Uint32 Rmask, Gmask, Bmask, Amask;	   /* masks for desired format */
	int bpp;							   /* bits per pixel for desired format */
	/* load the bmp */
	bmp_surface = SDL_LoadBMP("icon.bmp");
	if (bmp_surface == NULL) {
		fatalError("could not load bmp");
	}
	/* set white to transparent on the happyface */
	SDL_SetColorKey(bmp_surface, 1, SDL_MapRGB(bmp_surface->format, 255, 255, 255));
	SDL_PixelFormatEnumToMasks(format, &bpp, &Rmask, &Gmask, &Bmask, &Amask);
	/*
	   create a new RGBA surface and blit the bmp to it
	   this is an extra step, but it seems to be necessary
	   is this a bug?
	 */
	bmp_surface_rgba = SDL_CreateRGBSurface(0, bmp_surface->w, bmp_surface->h, bpp, Rmask, Gmask, Bmask, Amask);	
	SDL_BlitSurface(bmp_surface, NULL, bmp_surface_rgba, NULL);
	
	/* convert RGBA surface to texture */
	texture_id = SDL_CreateTextureFromSurface(format, bmp_surface_rgba);
	if (texture_id == 0) {
		fatalError("could not create texture");
	}
	SDL_SetTextureBlendMode(texture_id, SDL_TEXTUREBLENDMODE_BLEND);
	
	/* free up allocated memory */
	SDL_FreeSurface(bmp_surface_rgba);
	SDL_FreeSurface(bmp_surface);
}

int main(int argc, char *argv[]) {

	SDL_WindowID windowID;
	Uint32 startFrame;
	Uint32 endFrame;
	Uint32 delay;
	int done;
	
	/* initialize SDL */
	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
		fatalError("Could not initialize SDL");
	}
	windowID = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,\
								SDL_WINDOW_OPENGL|SDL_WINDOW_SHOWN|SDL_WINDOW_BORDERLESS);
	
	SDL_CreateRenderer(windowID, -1, 0);
	
	initializeTexture();
	initializeHappyFaces();
			
	/* main loop */
	done = 0;
	while(!done) {
		startFrame = SDL_GetTicks();
		SDL_Event event;
        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
				done = 1;
            }
        }
		render();
		endFrame = SDL_GetTicks();
		
		/* figure out how much time we have left, and then sleep */
		delay = MILLESECONDS_PER_FRAME - (endFrame - startFrame);
		if (delay < 0) {
			delay = 0;
		} else if (delay > MILLESECONDS_PER_FRAME) {
			delay = MILLESECONDS_PER_FRAME;
		}
		SDL_Delay(delay);
	}
	
	/* cleanup */
	SDL_DestroyTexture(texture_id);
	/* shutdown SDL */
	SDL_Quit();

	return 0;
	
}