/*
 * gdk-pixbuf-io.c: Code to load images into GdkPixBufs
 *
 * Author:
 *    Miguel de Icaza (miguel@gnu.org)
 */
#include <config.h>
#include <stdio.h>
#include <glib.h>
#include <gmodule.h>
#include "gdk-pixbuf.h"

static gboolean
pixbuf_check_png (unsigned char *buffer, int size)
{
	if (size < 28)
		return FALSE;

	if (buffer [0] != 0x89 ||
	    buffer [1] != 'P' ||
	    buffer [2] != 'N' ||
	    buffer [3] != 'G' ||
	    buffer [4] != 0x0d ||
	    buffer [5] != 0x0a ||
	    buffer [6] != 0x1a ||
	    buffer [7] != 0x0a)
		return FALSE;

	return TRUE;
}

static gboolean
pixbuf_check_jpeg (unsigned char *buffer, int size)
{
	if (size < 10)
		return FALSE;

	if (buffer [0] != 0xff || buffer [1] != 0xd8)
		return FALSE;
	
	return TRUE;
}

static gboolean
pixbuf_check_tiff (unsigned char *buffer, int size)
{
	if (size < 10)
		return FALSE;

	if (buffer [0] == 'M' && buffer [1] == 'M' && buffer [2] == 0 && buffer [3] == 0x2a)
		return TRUE;

	if (buffer [0] == 'I' && buffer [1] == 'I' && buffer [2] == 0x2a && buffer [3] == 0)
		return TRUE;
	
	return FALSE;
}

static gboolean
pixbuf_check_gif (unsigned char *buffer, int size)
{
	if (size < 20)
		return FALSE;
		
	if (strncmp (buffer, "GIF8", 4) == 0)
		return TRUE;
	
	return FALSE;
}

static gboolean
pixbuf_check_xpm (unsigned char *buffer, int size)
{
	if (size < 20)
		return FALSE;
	
	if (strncmp (buffer, "/* XPM */", 9) == 0)
		return TRUE;
	
	return FALSE;
}

static gboolean
pixbuf_check_bmp (unsigned char *buffer, int size)
{
	if (size < 20)
		return FALSE;
	
	if (buffer [0] != 'B' || buffer [1] != 'M')
		return FALSE;
	
	return TRUE;
}

static gboolean
pixbuf_check_ppm (unsigned char *buffer, int size)
{
	if (size < 20)
		return FALSE;

	if (buffer [0] == 'P'){
		if (buffer [1] == '1' ||
		    buffer [1] == '2' ||
		    buffer [1] == '3' ||
		    buffer [1] == '4' ||
		    buffer [1] == '5' ||
		    buffer [1] == '6')
			return TRUE;
	}
	return FALSE;
}

static struct {
	char      *module_name;
	gboolean   (*format_check)(unsigned char *buffer, int size);
	GModule   *module;
	GdkPixBuf *(*load)(FILE *f);
	int        (*save)(char *filename, ...);
} file_formats [] = {
	{ "png",  pixbuf_check_png,  NULL, NULL, NULL },
	{ "jpeg", pixbuf_check_jpeg, NULL, NULL, NULL },
	{ "tiff", pixbuf_check_tiff, NULL, NULL, NULL },
	{ "gif",  pixbuf_check_gif,  NULL, NULL, NULL },
	{ "xpm",  pixbuf_check_xpm,  NULL, NULL, NULL },
/*	{ "bmp",  pixbuf_check_bmp,  NULL, NULL, NULL },
	{ "ppm",  pixbuf_check_ppm,  NULL, NULL, NULL },*/
	{ NULL, NULL, NULL, NULL, NULL }
};

static int
image_file_format (const char *file)
{
	FILE *f = fopen (file, "r");

	if (!f)
		return -1;
}

static void
image_handler_load (int idx)
{
	char *module_name = g_strconcat ("pixbuf-", file_formats [idx].module_name, NULL);
	char *path;
	GModule *module;
	void *load_sym, *save_sym;
	
	path = g_module_build_path (PIXBUF_LIBDIR, module_name);
	g_free (module_name);

	module = g_module_open (path, G_MODULE_BIND_LAZY);
	if (!module)
		return;
	
	file_formats [idx].module = module;

	if (g_module_symbol (module, "image_load", &load_sym))
		file_formats [idx].load = load_sym;

	if (g_module_symbol (module, "image_save", &save_sym))
		file_formats [idx].save = save_sym;
}

GdkPixBuf *
gdk_pixbuf_load_image (const char *file)
{
	GdkPixBuf *pixbuf;
	gint n, i;
	FILE *f;
	char buffer [128];

	f = fopen (file, "r");
	if (!f)
		return NULL;
	n = fread (&buffer, 1, sizeof (buffer), f);

	if (n == 0){
		fclose (f);		
		return NULL;
	}

	for (i = 0; file_formats [i].module_name; i++){
		if ((*file_formats [i].format_check)(buffer, n)){
			if (!file_formats [i].load)
				image_handler_load (i);

			if (!file_formats [i].load){
				fclose (f);
				return NULL;
			}

			fseek(f, 0, SEEK_SET);
			pixbuf = (*file_formats [i].load)(f);
			fclose (f);
			return pixbuf;
		}
	}

	fclose (f);
	return NULL;
}