/*
	Quick SDL2 wrapper for uPNG
	d@revenant1.net
	
	This code is public domain.
*/

// https://github.com/elanthis/upng
#include "upng/upng.h"
#include <SDL2/SDL.h>

SDL_Surface* PNG_Load(const char *file);
SDL_Surface* PNG_LoadMem(const unsigned char *data, unsigned size);

static const char *PNG_error[] = {
	"no error",
	"out of memory",
	"file not found",
	"not a PNG file",
	"invalid PNG image",
	"unsupported PNG chunk",
	"image interlacing not supported",
	"unsupported color format",
	"invalid parameter",
};

static SDL_Surface* PNG_Decode(upng_t *png) {
	SDL_Surface *s = 0;

	uint8_t *out, *in;
	unsigned inpitch, format;

	if (!png || upng_decode(png) != UPNG_EOK) goto end;
	
	// get format of decoded PNG
	switch (upng_get_format(png)) {
	case UPNG_RGB8:
		format = SDL_PIXELFORMAT_RGB24;
		break;
		
	case UPNG_RGBA8:
		format = SDL_PIXELFORMAT_RGBA32;
		break;
		
	default:
		// unsupported
		SDL_SetError("SDL_upng: only RGB24 and RGBA32 are supported");
		goto end;
	}
	
	s = SDL_CreateRGBSurfaceWithFormat(0,
		upng_get_width(png), upng_get_height(png), 
		upng_get_bpp(png), format);
	if (!s) goto end;
	
	// copy decoded image
	SDL_LockSurface(s);
	
	out = (uint8_t*)s->pixels;
	in = (uint8_t*)upng_get_buffer(png);
	/* 
	upng_get_pixelsize is supposed to return bytes, but returns bits instead...
	Just use upng_get_bpp in case that gets fixed later
	(https://github.com/elanthis/upng/pull/6)
	*/
	inpitch = s->w * ((upng_get_bpp(png)+7) / 8);
	
	for (int i = 0; i < s->h; i++) {
		memcpy(out, in, inpitch);
		out += s->pitch;
		in += inpitch;
	}
	
	SDL_UnlockSurface(s);
end:
	if (png) {
		if (upng_get_error(png)) {
			SDL_SetError("uPNG: %s", PNG_error[upng_get_error(png)]);
		}
		upng_free(png);
	} else {
		SDL_SetError("SDL_upng: couldn't allocate PNG info");
	}
	return s;
}

SDL_Surface* PNG_Load(const char *file) {
	upng_t *png = upng_new_from_file(file);
	return PNG_Decode(png);
}

SDL_Surface* PNG_LoadMem(const unsigned char *data, unsigned size) {
	upng_t *png = upng_new_from_bytes(data, size);
	return PNG_Decode(png);
}