// With much thanks to https://benedicthenshaw.com/soft_render_sdl2.html

// --- SETTINGS ---
// BUFFER
// How to buffer pixels.
// 0: Use SDL_Surface (fastest in software)
// 1: Use SDL_Renderer (slow?)
// TODO: Add support for GPU texture
#define ENGINE_SDL_BUFFERTYPE 0

// TRANSPARENCY
// How to draw transparent pixels (SDL_Surface buffer only).
// 0: Do not handle transparency (Fastest but non-square textures will have a halo around them)
// 1: 1-bit transparency (Alpha values under 128 are not drawn)
// 2: 8-bit transparency (Nice but slow)
// TODO: Add support for SDL_Renderer
#define ENGINE_SDL_TRANSPARENCY 1

// --- HACKS ---
// BUFFER
// Use static color conversion. This will speed up rendering, however, the wrong colors may be displayed depending on platform. This only has an effect if ENGINE_SDL_BUFFERTYPE is set to 0.
// 0 = Disable
// 1 = RGBA (raw)
// 2 = BGRA (common)
// TODO: Add custom mode with quicker conversion of known types, and slow conversion for unknown types.
#define ENGINE_SDL_COLOR 2

// INTEGER UPSCALING
// 2 makes the surface scaled 2x, 3 = 3x, etc.
// TODO: Fix ENGINE_SDL_TRANSPARENCY 2
#define ENGINE_SDL_SCALE 5

// SKIP: COLOR
// Skip setting colors every X requests. Set to 2 to skip every second request, 3 for every third, etc.
#define ENGINE_SDL_SKIP_COLOR_INTERVAL 0 // 2
// How many requests to skip, when a skip is encountered.
#define ENGINE_SDL_SKIP_COLOR_AMOUNT 2
// Whether to alternate fields. TODO
#define ENGINE_SDL_SKIP_COLOR_ALTERNATE 0

// SKIP: PIXEL
// Skip setting pixel every X requests.
#define ENGINE_SDL_SKIP_PIXEL_INTERVAL 0 // 2
#define ENGINE_SDL_SKIP_PIXEL_AMOUNT 2
#define ENGINE_SDL_SKIP_PIXEL_ALTERNATE 0

// SKIP: FRAME
#define ENGINE_SDL_SKIP_FRAME_INTERVAL 1
#define ENGINE_SDL_SKIP_FRAME_AMOUNT 1
// Entirely skip changing any colors and pixels on skipped frames, without this, this is pretty useless
#define ENGINE_SDL_SKIP_FRAME_DROP 0

// DO NOT TOUCH THESE
#if (ENGINE_SDL_SKIP_COLOR_INTERVAL > 0 && ENGINE_SDL_SKIP_COLOR_AMOUNT > 0)
	#define ENGINE_SDL_SKIP_COLOR 1
#endif

#if (ENGINE_SDL_SKIP_PIXEL_INTERVAL > 0 && ENGINE_SDL_SKIP_PIXEL_AMOUNT > 0)
	#define ENGINE_SDL_SKIP_PIXEL 1
#endif

#if (ENGINE_SDL_SKIP_FRAME_INTERVAL > 0 && ENGINE_SDL_SKIP_FRAME_AMOUNT > 0)
	#define ENGINE_SDL_SKIP_FRAME 1
#endif

#include <SDL2/SDL.h>
SDL_Window * engine_sdl_window;

#if (ENGINE_SDL_BUFFERTYPE == 0)
	SDL_Surface * engine_sdl_surface;
	Uint32 * engine_sdl_pixels;
#endif

#if (ENGINE_SDL_BUFFERTYPE == 1)
	SDL_Renderer * engine_sdl_renderer;
#endif

int engine_width = 0;
int engine_height = 0;

struct ENGINE_EVENT engine_getEvent() {
	struct ENGINE_EVENT event;
	SDL_Event sdlevent;
	
	if (!SDL_PollEvent(&sdlevent)) {
		struct ENGINE_EVENT_NONE data;
		event.type = ENGINE_EVENT_TYPE_NONE;
		event.data = &data;
		return event;
	}
	
	if (sdlevent.type == SDL_QUIT) {
		struct ENGINE_EVENT_EXIT data;
		event.type = ENGINE_EVENT_TYPE_EXIT;
		event.data = &data;
		return event;
	}
	
	if (sdlevent.type == SDL_KEYDOWN || sdlevent.type == SDL_KEYUP) {
		if (sdlevent.key.repeat != 0) { goto unknown; }
		struct ENGINE_EVENT_INPUTKB data;
		data.pressed = (sdlevent.type == SDL_KEYDOWN);
		data.key = sdlevent.key.keysym.scancode;
		event.type = ENGINE_EVENT_TYPE_INPUTKB;
		event.data = &data;
		return event;
	}
	
	unknown:
	struct ENGINE_EVENT_UNKNOWN data;
	event.type = ENGINE_EVENT_TYPE_UNKNOWN;
	event.data = &data;
	return event;
}

void engine_sleep(long long ms) {
	SDL_Delay(ms);
}

long long engine_time_get() {
	return SDL_GetTicks();
}

#ifdef ENGINE_SDL_SKIP_FRAME
	char engine_sdl_skipf_interval = 0;
	char engine_sdl_skipf_amount = 0;
#endif

#ifdef ENGINE_SDL_SKIP_COLOR
	char engine_sdl_skipc_interval = 0;
	char engine_sdl_skipc_amount = 0;
#endif

Uint32 engine_sdl_color;
void engine_setColor(char r,char g,char b,char a) {
	#ifdef ENGINE_SDL_SKIP_COLOR
		if (engine_sdl_skipc_interval == 0) {
			if (engine_sdl_skipc_amount == 0) {
				engine_sdl_skipc_interval = ENGINE_SDL_SKIP_COLOR_INTERVAL - 1;
				engine_sdl_skipc_amount = ENGINE_SDL_SKIP_COLOR_AMOUNT;
			} else {
				--engine_sdl_skipc_amount;
				return;
			}
		} else {
			--engine_sdl_skipc_interval;
		}
	#endif
	
	#if (ENGINE_SDL_SKIP_FRAME == 1 && ENGINE_SDL_SKIP_FRAME_DROP == 1)
		if (engine_sdl_skipf_interval == 0 && engine_sdl_skipf_amount > 0) {
			return;
		}
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 0)
		#if (ENGINE_SDL_COLOR != 0 || ENGINE_SDL_TRANSPARENCY > 0)
			Uint8 * rawcolor = (Uint8 *)&engine_sdl_color; // is doing this ok?
		#endif
		
		#if (ENGINE_SDL_COLOR == 1)
			rawcolor[0] = (Uint8)r;
			rawcolor[1] = (Uint8)g;
			rawcolor[2] = (Uint8)b;
			rawcolor[3] = (Uint8)a;
		#elif (ENGINE_SDL_COLOR == 2)
			rawcolor[0] = (Uint8)b;
			rawcolor[1] = (Uint8)g;
			rawcolor[2] = (Uint8)r;
			rawcolor[3] = (Uint8)a;
		#else
			engine_sdl_color = SDL_MapRGBA(engine_sdl_surface->format,(Uint8)r,(Uint8)g,(Uint8)b,(Uint8)a);
			#if (ENGINE_SDL_TRANSPARENCY > 0)
				rawcolor[3] = (Uint8)a;
			#endif
		#endif
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 1)
		SDL_SetRenderDrawColor(engine_sdl_renderer,r,g,b,a);
	#endif
}

#ifdef ENGINE_SDL_SKIP_PIXEL
	char engine_sdl_skipp_interval = 0;
	char engine_sdl_skipp_amount = 0;
#endif

void engine_drawPixel(int x,int y) {
	#ifdef ENGINE_SDL_SKIP_PIXEL
		if (engine_sdl_skipp_interval == 0) {
			if (engine_sdl_skipp_amount == 0) {
				engine_sdl_skipp_interval = ENGINE_SDL_SKIP_PIXEL_INTERVAL - 1;
				engine_sdl_skipp_amount = ENGINE_SDL_SKIP_PIXEL_AMOUNT;
			} else {
				--engine_sdl_skipp_amount;
				return;
			}
		} else {
			--engine_sdl_skipp_interval;
		}
	#endif
	
	#if (ENGINE_SDL_SKIP_FRAME == 1 && ENGINE_SDL_SKIP_FRAME_DROP == 1)
		if (engine_sdl_skipf_interval == 0 && engine_sdl_skipf_amount > 0) {
			return;
		}
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 0)
		#if (ENGINE_SDL_TRANSPARENCY == 1)
			if (((Uint8 *)&engine_sdl_color)[3] < 128) { // is doing this ok?
				return;
			}
		#endif
		
		#if (ENGINE_SDL_TRANSPARENCY == 2)
			Uint8 * rawcolor = (Uint8 *)&engine_sdl_color;
			if (rawcolor[3] < 255) {
				Uint8 * sourcecolor = (Uint8 *)&engine_sdl_pixels[x + y * engine_width];
				float alpha = (float)rawcolor[3] / 255;
				sourcecolor[0] = sourcecolor[0] + ((rawcolor[0] - sourcecolor[0])*alpha);
				sourcecolor[1] = sourcecolor[1] + ((rawcolor[1] - sourcecolor[1])*alpha);
				sourcecolor[2] = sourcecolor[2] + ((rawcolor[2] - sourcecolor[2])*alpha);
				return;
			}
		#endif
		
		#if (ENGINE_SDL_SCALE == 1)
			engine_sdl_pixels[x + y * engine_width] = engine_sdl_color;
		#else
			char xi = 0;
			while (xi < ENGINE_SDL_SCALE) {
				char yi = 0;
				while (yi < ENGINE_SDL_SCALE) {
					engine_sdl_pixels[((x * ENGINE_SDL_SCALE) + xi) + ((y * ENGINE_SDL_SCALE) + yi) * (engine_width * ENGINE_SDL_SCALE)] = engine_sdl_color;
					++yi;
				}
				++xi;
			}
		#endif
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 1)
		SDL_RenderDrawPoint(engine_sdl_renderer,x,y);
	#endif
}

void engine_render() {
	#ifdef ENGINE_SDL_SKIP_FRAME
		if (engine_sdl_skipf_interval == 0) {
			if (engine_sdl_skipf_amount == 0) {
				engine_sdl_skipf_interval = ENGINE_SDL_SKIP_FRAME_INTERVAL - 1;
				engine_sdl_skipf_amount = ENGINE_SDL_SKIP_FRAME_AMOUNT;
			} else {
				--engine_sdl_skipf_amount;
				return;
			}
		} else {
			--engine_sdl_skipf_interval;
		}
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 0)
		SDL_UpdateWindowSurface(engine_sdl_window);
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 1)
		SDL_RenderPresent(engine_sdl_renderer);
	#endif
}

void engine_init(int width,int height,char *title) {
	SDL_Init(SDL_INIT_VIDEO);
	engine_sdl_window = SDL_CreateWindow(title,SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,width * ENGINE_SDL_SCALE,height * ENGINE_SDL_SCALE,0);
	#if (ENGINE_SDL_BUFFERTYPE == 0)
		engine_sdl_surface = SDL_GetWindowSurface(engine_sdl_window);
		engine_sdl_pixels = engine_sdl_surface->pixels;
	#endif
	
	#if (ENGINE_SDL_BUFFERTYPE == 1)
		engine_sdl_renderer = SDL_CreateRenderer(engine_sdl_window,-1,0);
	#endif
	
	engine_width = width;
	engine_height = height;
	
	#if (ENGINE_SDL_BUFFERTYPE == 1)
		engine_setColor(0,0,0,255);
		#ifdef ENGINE_SDL_SKIP_COLOR
			engine_sdl_skipc_interval = 0;
			engine_sdl_skipc_amount = 0;
		#endif
		SDL_RenderClear(engine_sdl_renderer);
	#endif
}