/* this file is part of evince, a gnome document viewer
 *
 *  Copyright (C) 2007 Carlos Garcia Campos <carlosgc@gnome.org>
 *
 * Evince is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Evince is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */

#include <config.h>

#include <glib/gstdio.h>

#include "ev-module.h"
#include "ev-backends-manager.h"

static GList *ev_backends_list = NULL;

typedef struct _EvBackendInfo EvBackendInfo;
struct _EvBackendInfo {
	gchar       *module_name;
	GTypeModule *module;
	gboolean     resident;

	GType        type_id;

	gchar       *type_desc;
	gchar      **mime_types;
};

#define EV_BACKENDS_GROUP     "Evince Backend"
#define EV_BACKENDS_EXTENSION ".evince-backend"

static void
ev_backend_info_free (EvBackendInfo *info)
{
	g_free (info->module_name);
	g_free (info->type_desc);
	g_strfreev (info->mime_types);
	g_free (info);
}

static EvBackendInfo *
ev_backends_manager_load_backend (const gchar *file)
{
	EvBackendInfo *info;
	GKeyFile      *backend_file = NULL;
	GError        *error = NULL;

	backend_file = g_key_file_new ();
	if (!g_key_file_load_from_file (backend_file, file, G_KEY_FILE_NONE, &error)) {
		g_warning ("Error opening backend file %s: %s",
			   file, error->message);
		g_error_free (error);
		g_key_file_free (backend_file);

		return NULL;
	}

	info = g_new0 (EvBackendInfo, 1);
	info->module_name = g_key_file_get_string (backend_file, EV_BACKENDS_GROUP,
						   "Module", NULL);
	if (!info->module_name) {
		g_warning ("Bad evince backend file %s: Could not find 'Module'",
			   file);
		ev_backend_info_free (info);
		g_key_file_free (backend_file);

		return NULL;
	}

	info->resident = g_key_file_get_boolean (backend_file, EV_BACKENDS_GROUP,
						 "Resident", NULL);
	
	info->type_desc = g_key_file_get_locale_string (backend_file, EV_BACKENDS_GROUP,
							"TypeDescription", NULL, NULL);
	if (!info->type_desc) {
		g_warning ("Bad evince backend file %s: Could not find 'TypeDescription'",
			   file);
		ev_backend_info_free (info);
		g_key_file_free (backend_file);

		return NULL;
	}

	info->mime_types = g_key_file_get_string_list (backend_file, EV_BACKENDS_GROUP,
						       "MimeType", NULL, NULL);
	if (!info->mime_types) {
		g_warning ("Bad evince backend file %s: Could not find 'MimeType'",
			   file);
		ev_backend_info_free (info);
		g_key_file_free (backend_file);

		return NULL;
	}

	g_key_file_free (backend_file);

	return info;
}

static gboolean
ev_backends_manager_load (void)
{
	GDir        *dir;
	const gchar *dirent;
	GError      *error = NULL;

	dir = g_dir_open (EV_BACKENDSDIR, 0, &error);
	if (!dir) {
		g_warning ("%s", error->message);
		g_error_free (error);

		return FALSE;
	}

	while ((dirent = g_dir_read_name (dir))) {
		EvBackendInfo *info;
		gchar         *file;
		
		if (!g_str_has_suffix (dirent, EV_BACKENDS_EXTENSION))
			continue;

		file = g_build_filename (EV_BACKENDSDIR, dirent, NULL);
		info = ev_backends_manager_load_backend (file);
		g_free (file);

		if (!info)
			continue;
		
		ev_backends_list = g_list_prepend (ev_backends_list, info);
	}

	g_dir_close (dir);

	return ev_backends_list != NULL;
}

/*
 * _ev_backends_manager_init:
 *
 * Initializes the evince backends manager.
 *
 * Returns: %TRUE if there were any backends found; %FALSE otherwise
 */
gboolean
_ev_backends_manager_init (void)
{
	if (ev_backends_list)
		return TRUE;

	return ev_backends_manager_load ();
}

/*
 * _ev_backends_manager_shutdown:
 *
 * Shuts the evince backends manager down.
 */
void
_ev_backends_manager_shutdown (void)
{
	g_list_foreach (ev_backends_list, (GFunc)ev_backend_info_free, NULL);
	g_list_free (ev_backends_list);
	ev_backends_list = NULL;
}

static EvBackendInfo *
ev_backends_manager_get_backend_info (const gchar *mime_type)
{
	GList *l;

	for (l = ev_backends_list; l; l = g_list_next (l)) {
		EvBackendInfo *info;
		gint           i = 0;
		const char    *mime;
		
		info = (EvBackendInfo *)l->data;
		
		while ((mime = info->mime_types[i++])) {
			if (g_ascii_strcasecmp (mime, mime_type) == 0)
				return info;
		}
	}

	return NULL;
}

EvDocument *
ev_backends_manager_get_document (const gchar *mime_type)
{
	EvDocument    *document;
	EvBackendInfo *info;

	info = ev_backends_manager_get_backend_info (mime_type);
	if (!info)
		return NULL;

	if (!info->module) {
		gchar *path;
		
		path = g_module_build_path (EV_BACKENDSDIR, info->module_name);
		info->module = G_TYPE_MODULE (ev_module_new (path, info->resident));
		g_free (path);
	}
	
	if (!g_type_module_use (info->module)) {
		g_warning ("Cannot load backend '%s' since file '%s' cannot be read.",
			   info->module_name,
			   ev_module_get_path (EV_MODULE (info->module)));
		g_object_unref (G_OBJECT (info->module));
		info->module = NULL;

		return NULL;
	}

	document = EV_DOCUMENT (ev_module_new_object (EV_MODULE (info->module)));
	g_type_module_unuse (info->module);

	return document;
}

static EvBackendInfo *
get_document_backend_info (EvDocument *document)
{
	GList *l;

	for (l = ev_backends_list; l; l = g_list_next (l)) {
		EvBackendInfo *info;
		GType          type_id;

		info = (EvBackendInfo *)l->data;

		if (!info->module)
			continue;

		type_id = ev_module_get_object_type (EV_MODULE (info->module));

		if (G_TYPE_CHECK_INSTANCE_TYPE (document, type_id)) {
			return info;
		}
	}

	return NULL;
}

const gchar *
ev_backends_manager_get_document_module_name (EvDocument *document)
{
	EvBackendInfo *info;

	info = get_document_backend_info (document);
	return info ? info->module_name : NULL;
}

static EvTypeInfo *
ev_type_info_new (const gchar *desc, const gchar **mime_types)
{
	EvTypeInfo *info;

	info = g_new (EvTypeInfo, 1);

	info->desc = desc;
	info->mime_types = mime_types;

	return info;
}

EvTypeInfo *
ev_backends_manager_get_document_type_info (EvDocument *document)
{
	EvBackendInfo *info;

	info = get_document_backend_info (document);
	return info ?
		ev_type_info_new (info->type_desc,
				  (const gchar **)info->mime_types)
		: NULL;
}

GList *
ev_backends_manager_get_all_types_info (void)
{
	GList *l;
	GList *retval = NULL;

	for (l = ev_backends_list; l; l = g_list_next (l)) {
		EvBackendInfo *info;
		EvTypeInfo    *type_info;

		info = (EvBackendInfo *)l->data;

		type_info = ev_type_info_new (info->type_desc,
					      (const gchar **)info->mime_types);
		retval = g_list_prepend (retval, type_info);
	}

	return retval;
}