/*
 * sdl12shim.c - see sdl12shim.h.
 *
 * Written for fredygames.com to build Berusky for the browser with Emscripten's SDL2 port.
 * Copyright (C) 2026 FredyGames. Same license as Berusky: GNU GPL version 2 or later.
 */
#include "sdl12shim.h"

#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#endif

static SDL_Window *window = NULL;
static Uint32 window_id = 0;
static SDL_Renderer *renderer = NULL;
static SDL_Texture *texture = NULL;
static SDL_Surface *screen = NULL;
static int key_repeat = 0;

/* SDL 1.2 only repeats keys when the game asks for it. */
static int SDLCALL filter_events(void *userdata, SDL_Event *ev)
{
	(void)userdata;
	if(ev->type == SDL_KEYDOWN && ev->key.repeat && !key_repeat)
		return 0;
	return 1;
}

SDL_Surface *SDL_SetVideoMode(int width, int height, int bpp, Uint32 flags)
{
	(void)bpp;
	(void)flags;
	/* The game quits and restarts the video subsystem before each mode change, which takes the
	 * window and everything on it along. */
	if(window && SDL_GetWindowFromID(window_id) != window) {
		window = NULL;
		renderer = NULL;
		texture = NULL;
	}
	if(texture)
		SDL_DestroyTexture(texture);
	texture = NULL;
	/* The game frees the old screen surface itself (it owns the pointer it was given). */
	screen = NULL;
	if(!window) {
		window = SDL_CreateWindow("Berusky", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
				width, height, 0);
		if(!window)
			return NULL;
		window_id = SDL_GetWindowID(window);
		renderer = SDL_CreateRenderer(window, -1, 0);
		if(!renderer)
			return NULL;
		SDL_SetEventFilter(filter_events, NULL);
	}
	else
		SDL_SetWindowSize(window, width, height);
	SDL_RenderSetLogicalSize(renderer, width, height);
	texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGB888, SDL_TEXTUREACCESS_STREAMING,
			width, height);
	screen = SDL_CreateRGBSurfaceWithFormat(0, width, height, 32, SDL_PIXELFORMAT_RGB888);
	if(!texture || !screen)
		return NULL;
	return screen;
}

static void present(void)
{
	if(!screen || !texture)
		return;
	SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
	SDL_RenderClear(renderer);
	SDL_RenderCopy(renderer, texture, NULL, NULL);
	SDL_RenderPresent(renderer);
}

void SDL_UpdateRects(SDL_Surface *s, int numrects, SDL_Rect *rects)
{
	(void)s;
	(void)numrects;
	(void)rects;
	present();
}

void SDL_UpdateRect(SDL_Surface *s, Sint32 x, Sint32 y, Uint32 w, Uint32 h)
{
	(void)s;
	(void)x;
	(void)y;
	(void)w;
	(void)h;
	present();
}

/* Full screen is the player's button on the page; the game's menu option does nothing here. */
int SDL_WM_ToggleFullScreen(SDL_Surface *surface)
{
	(void)surface;
	return 0;
}

/* The page keeps its own title. */
void SDL_WM_SetCaption(const char *title, const char *icon)
{
	(void)title;
	(void)icon;
}

int SDL_EnableKeyRepeat(int delay, int interval)
{
	(void)interval;
	key_repeat = delay > 0;
	return 0;
}

int SDL_SetAlpha(SDL_Surface *surface, Uint32 flags, Uint8 alpha)
{
	if(flags & SDL_SRCALPHA) {
		SDL_SetSurfaceAlphaMod(surface, alpha);
		return SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_BLEND);
	}
	SDL_SetSurfaceAlphaMod(surface, 255);
	return SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE);
}

/* SDL 1.2's DisplayFormat converted to the screen format and dropped any alpha channel. */
SDL_Surface *SDL_DisplayFormat(SDL_Surface *surface)
{
	SDL_Surface *s = SDL_ConvertSurfaceFormat(surface, SDL_PIXELFORMAT_RGB888, 0);
	if(s)
		SDL_SetSurfaceBlendMode(s, SDL_BLENDMODE_NONE);
	return s;
}