// Mostly for fun (but can very slightly increase performance for large textures). If set to 1, does not clear texture's affiliated and leaves garbage.
#define ENGINE_GENERIC_TEXTURE_NOCLEAR 1

struct ENGINE_TEXTURE { int width; int height; void * fe_texture; };
struct ENGINE_GENERIC_TEXTURE { char * pixels; };

struct ENGINE_TEXTURE * engine_createTexture(int width,int height) {
	// frontend texture
	char * pixels = engine_malloc(NULL,sizeof(char) * width * height * 4);
	#if (ENGINE_GENERIC_TEXTURE_NOCLEAR == 0)
		memset(pixels,0,sizeof(char) * width * height * 4);
	#endif
	struct ENGINE_GENERIC_TEXTURE * fe_texture = engine_malloc(NULL,sizeof(struct ENGINE_GENERIC_TEXTURE));
	fe_texture->pixels = pixels;
	
	// engine texture
	struct ENGINE_TEXTURE * texture = engine_malloc(NULL,sizeof(struct ENGINE_TEXTURE));
	texture->width = width;
	texture->height = height;
	texture->fe_texture = (void *)fe_texture;
	return texture;
}

struct ENGINE_GENERIC_TEXTURE_COLOR { char r; char g; char b; char a; };
struct ENGINE_GENERIC_TEXTURE_COLOR engine_generic_texture_color;

void engine_textureSetColor(char r,char g,char b,char a) {
	engine_generic_texture_color.r = r;
	engine_generic_texture_color.g = g;
	engine_generic_texture_color.b = b;
	engine_generic_texture_color.a = a;
}

void engine_textureDrawPixel(struct ENGINE_TEXTURE * texture,int x,int y) {
	char * pixels = ((struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture))->pixels;
	long pixelIndex = (x + y * texture->width) * 4;
	pixels[pixelIndex + 0] = engine_generic_texture_color.r;
	pixels[pixelIndex + 1] = engine_generic_texture_color.g;
	pixels[pixelIndex + 2] = engine_generic_texture_color.b;
	pixels[pixelIndex + 3] = engine_generic_texture_color.a;
}

void engine_textureDestroy(struct ENGINE_TEXTURE * texture) {
	struct ENGINE_GENERIC_TEXTURE * fe_texture = (struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture);
	engine_free(fe_texture->pixels);
	engine_free(fe_texture);
	engine_free(texture);
}

void engine_renderTexture2D(struct ENGINE_TEXTURE * texture,int sx,int sy) {
	char * pixels = ((struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture))->pixels;
	int ex = sx + texture->width;
	if (ex > engine_width) { ex = engine_width; }
	int ey = sy + texture->height;
	if (ey > engine_width) { ey = engine_height; }
	int x = sx;
	if (x < 0) { x = 0; }
	int y = sy;
	if (y < 0) { y = 0; }
	long pixelIndex = 0;
	
	while (y < ey) {
		while (x < ex) {
			pixelIndex = ((x - sx) + (y - sy) * texture->width)*4;
			engine_setColor(pixels[pixelIndex],pixels[pixelIndex + 1],pixels[pixelIndex + 2],pixels[pixelIndex + 3]);
			engine_drawPixel(x,y);
			++x;
		}
		x = sx;
		++y;
	}
}

void engine_fileToTexture(struct ENGINE_TEXTURE * texture,char * fpath) {
	FILE * f = fopen(fpath,"r");
	fgets(((struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture))->pixels,texture->width * texture->height,f);
	fclose(f);
}