/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * xedit-metadata-manager.c
 * This file is part of xedit
 *
 * Copyright (C) 2003-2007  Paolo Maggi 
 *
 * This program 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.
 *
 * This program 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., 51 Franklin St, Fifth Floor, 
 * Boston, MA 02110-1301, USA. 
 */
 
/*
 * Modified by the xedit Team, 2003-2007. See the AUTHORS file for a 
 * list of people on the xedit Team.  
 * See the ChangeLog files for a list of changes. 
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <time.h>
#include <stdlib.h>
#include <libxml/xmlreader.h>
#include "xedit-metadata-manager.h"
#include "xedit-debug.h"
#include "xedit-dirs.h"

/*
#define XEDIT_METADATA_VERBOSE_DEBUG	1
*/

#define METADATA_FILE 	"xedit-metadata.xml"

#define MAX_ITEMS	50

typedef struct _XeditMetadataManager XeditMetadataManager;

typedef struct _Item Item;

struct _Item
{
	time_t	 	 atime; /* time of last access */

	GHashTable	*values;
};
	
struct _XeditMetadataManager
{
	gboolean	 values_loaded; /* It is true if the file 
					   has been read */

	guint 		 timeout_id;

	GHashTable	*items;
};

static gboolean xedit_metadata_manager_save (gpointer data);


static XeditMetadataManager *xedit_metadata_manager = NULL;

static void
item_free (gpointer data)
{
	Item *item;
	
	g_return_if_fail (data != NULL);

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug (DEBUG_METADATA);
#endif

	item = (Item *)data;

	if (item->values != NULL)
		g_hash_table_destroy (item->values);

	g_free (item);
}

static void
xedit_metadata_manager_arm_timeout (void)
{
	if (xedit_metadata_manager->timeout_id == 0)
	{
		xedit_metadata_manager->timeout_id = 
			g_timeout_add_seconds_full (G_PRIORITY_DEFAULT_IDLE,
						    2,
						    (GSourceFunc)xedit_metadata_manager_save,
						    NULL,
						    NULL);
	}
}

static gboolean
xedit_metadata_manager_init (void)
{
	xedit_debug (DEBUG_METADATA);

	if (xedit_metadata_manager != NULL)
		return TRUE;

	xedit_metadata_manager = g_new0 (XeditMetadataManager, 1);

	xedit_metadata_manager->values_loaded = FALSE;

	xedit_metadata_manager->items = 
		g_hash_table_new_full (g_str_hash, 
				       g_str_equal, 
				       g_free,
				       item_free);

	return TRUE;
}

/* This function must be called before exiting xedit */
void
xedit_metadata_manager_shutdown (void)
{
	xedit_debug (DEBUG_METADATA);

	if (xedit_metadata_manager == NULL)
		return;

	if (xedit_metadata_manager->timeout_id)
	{
		g_source_remove (xedit_metadata_manager->timeout_id);
		xedit_metadata_manager->timeout_id = 0;
		xedit_metadata_manager_save (NULL);
	}

	if (xedit_metadata_manager->items != NULL)
		g_hash_table_destroy (xedit_metadata_manager->items);

	g_free (xedit_metadata_manager);
	xedit_metadata_manager = NULL;
}

static void
parseItem (xmlDocPtr doc, xmlNodePtr cur)
{
	Item *item;
	
	xmlChar *uri;
	xmlChar *atime;
	
#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug (DEBUG_METADATA);
#endif	

	if (xmlStrcmp (cur->name, (const xmlChar *)"document") != 0)
			return;

	uri = xmlGetProp (cur, (const xmlChar *)"uri");
	if (uri == NULL)
		return;
	
	atime = xmlGetProp (cur, (const xmlChar *)"atime");
	if (atime == NULL)
	{
		xmlFree (uri);
		return;
	}

	item = g_new0 (Item, 1);

	item->atime = g_ascii_strtoull ((char *)atime, NULL, 0);

	item->values = g_hash_table_new_full (g_str_hash, 
					      g_str_equal, 
					      g_free, 
					      g_free);

	cur = cur->xmlChildrenNode;

	while (cur != NULL)
	{
		if (xmlStrcmp (cur->name, (const xmlChar *)"entry") == 0)
		{
			xmlChar *key;
			xmlChar *value;

			key = xmlGetProp (cur, (const xmlChar *)"key");
			value = xmlGetProp (cur, (const xmlChar *)"value");

			if ((key != NULL) && (value != NULL))
				g_hash_table_insert (item->values,
						     g_strdup ((gchar *)key), 
						     g_strdup ((gchar *)value));

			if (key != NULL)
				xmlFree (key);
			if (value != NULL)
				xmlFree (value);
		}

		cur = cur->next;
	}

	g_hash_table_insert (xedit_metadata_manager->items,
			     g_strdup ((gchar *)uri),
			     item);

	xmlFree (uri);
	xmlFree (atime);
}

static gchar *
get_metadata_filename (void)
{
	gchar *cache_dir;
	gchar *metadata;

	cache_dir = xedit_dirs_get_user_cache_dir ();

	metadata = g_build_filename (cache_dir,
				     METADATA_FILE,
				     NULL);

	g_free (cache_dir);

	return metadata;
}

static gboolean
load_values (void)
{
	xmlDocPtr doc;
	xmlNodePtr cur;
	gchar *file_name;

	xedit_debug (DEBUG_METADATA);

	g_return_val_if_fail (xedit_metadata_manager != NULL, FALSE);
	g_return_val_if_fail (xedit_metadata_manager->values_loaded == FALSE, FALSE);

	xedit_metadata_manager->values_loaded = TRUE;
		
	xmlKeepBlanksDefault (0);

	/* FIXME: file locking - Paolo */
	file_name = get_metadata_filename ();
	if ((file_name == NULL) ||
	    (!g_file_test (file_name, G_FILE_TEST_EXISTS)))
	{
		g_free (file_name);
		return FALSE;
	}

	doc = xmlParseFile (file_name);
	g_free (file_name);

	if (doc == NULL)
	{
		return FALSE;
	}

	cur = xmlDocGetRootElement (doc);
	if (cur == NULL) 
	{
		g_message ("The metadata file '%s' is empty", METADATA_FILE);
		xmlFreeDoc (doc);
	
		return FALSE;
	}

	if (xmlStrcmp (cur->name, (const xmlChar *) "metadata")) 
	{
		g_message ("File '%s' is of the wrong type", METADATA_FILE);
		xmlFreeDoc (doc);
		
		return FALSE;
	}

	cur = xmlDocGetRootElement (doc);
	cur = cur->xmlChildrenNode;
	
	while (cur != NULL)
	{
		parseItem (doc, cur);

		cur = cur->next;
	}

	xmlFreeDoc (doc);

	return TRUE;
}

gchar *
xedit_metadata_manager_get (const gchar *uri,
			    const gchar *key)
{
	Item *item;
	gchar *value;

	g_return_val_if_fail (uri != NULL, NULL);
	g_return_val_if_fail (key != NULL, NULL);

	xedit_debug_message (DEBUG_METADATA, "URI: %s --- key: %s", uri, key );

	xedit_metadata_manager_init ();

	if (!xedit_metadata_manager->values_loaded)
	{
		gboolean res;

		res = load_values ();

		if (!res)
			return NULL;
	}

	item = (Item *)g_hash_table_lookup (xedit_metadata_manager->items,
					    uri);

	if (item == NULL)
		return NULL;

	item->atime = time (NULL);
	
	if (item->values == NULL)
		return NULL;

	value = g_hash_table_lookup (item->values, key);

	if (value == NULL)
		return NULL;
	else
		return g_strdup (value);
}

void
xedit_metadata_manager_set (const gchar *uri,
			    const gchar *key,
			    const gchar *value)
{
	Item *item;

	g_return_if_fail (uri != NULL);
	g_return_if_fail (key != NULL);

	xedit_debug_message (DEBUG_METADATA, "URI: %s --- key: %s --- value: %s", uri, key, value);
	
	xedit_metadata_manager_init ();

	if (!xedit_metadata_manager->values_loaded)
	{
		gboolean res;

		res = load_values ();

		if (!res)
			return;
	}

	item = (Item *)g_hash_table_lookup (xedit_metadata_manager->items,
					    uri);

	if (item == NULL)
	{
		item = g_new0 (Item, 1);

		g_hash_table_insert (xedit_metadata_manager->items,
				     g_strdup (uri),
				     item);
	}
	
	if (item->values == NULL)
		 item->values = g_hash_table_new_full (g_str_hash, 
				 		       g_str_equal, 
						       g_free, 
						       g_free);
	if (value != NULL)
		g_hash_table_insert (item->values,
				     g_strdup (key),
				     g_strdup (value));
	else
		g_hash_table_remove (item->values,
				     key);

	item->atime = time (NULL);

	xedit_metadata_manager_arm_timeout ();
}

static void
save_values (const gchar *key, const gchar *value, xmlNodePtr parent)
{
	xmlNodePtr xml_node;

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug (DEBUG_METADATA);
#endif	

	g_return_if_fail (key != NULL);
	
	if (value == NULL)
		return;
		
	xml_node = xmlNewChild (parent,
				NULL,
				(const xmlChar *)"entry",
				NULL);

	xmlSetProp (xml_node,
		    (const xmlChar *)"key",
		    (const xmlChar *)key);
	xmlSetProp (xml_node,
		    (const xmlChar *)"value",
		    (const xmlChar *)value);

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug_message (DEBUG_METADATA, "entry: %s = %s", key, value);
#endif	
}

static void
save_item (const gchar *key, const gpointer *data, xmlNodePtr parent)
{
	xmlNodePtr xml_node;
	const Item *item = (const Item *)data;
	gchar *atime;

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug (DEBUG_METADATA);
#endif

	g_return_if_fail (key != NULL);

	if (item == NULL)
		return;

	xml_node = xmlNewChild (parent, NULL, (const xmlChar *)"document", NULL);

	xmlSetProp (xml_node, (const xmlChar *)"uri", (const xmlChar *)key);

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug_message (DEBUG_METADATA, "uri: %s", key);
#endif	

	atime = g_strdup_printf ("%ld", item->atime);
	xmlSetProp (xml_node, (const xmlChar *)"atime", (const xmlChar *)atime);	

#ifdef XEDIT_METADATA_VERBOSE_DEBUG
	xedit_debug_message (DEBUG_METADATA, "atime: %s", atime);
#endif	

	g_free (atime);

    	g_hash_table_foreach (item->values,
			      (GHFunc)save_values,
			      xml_node);
}

static void
get_oldest (const gchar *key, const gpointer value, const gchar ** key_to_remove)
{
	const Item *item = (const Item *)value;

	if (*key_to_remove == NULL)
	{
		*key_to_remove = key;
	}
	else
	{
		const Item *item_to_remove = 
			g_hash_table_lookup (xedit_metadata_manager->items,
					     *key_to_remove);

		g_return_if_fail (item_to_remove != NULL);

		if (item->atime < item_to_remove->atime)
		{
			*key_to_remove = key;
		}
	}	
}

static void
resize_items (void)
{
	while (g_hash_table_size (xedit_metadata_manager->items) > MAX_ITEMS)
	{
		gpointer key_to_remove = NULL;

		g_hash_table_foreach (xedit_metadata_manager->items,
				      (GHFunc)get_oldest,
				      &key_to_remove);

		g_return_if_fail (key_to_remove != NULL);
		
		g_hash_table_remove (xedit_metadata_manager->items,
				     key_to_remove);
	}
}

static gboolean
xedit_metadata_manager_save (gpointer data)
{	
	xmlDocPtr  doc;
	xmlNodePtr root;
	gchar *file_name;

	xedit_debug (DEBUG_METADATA);

	xedit_metadata_manager->timeout_id = 0;

	resize_items ();
		
	xmlIndentTreeOutput = TRUE;

	doc = xmlNewDoc ((const xmlChar *)"1.0");
	if (doc == NULL)
		return TRUE;

	/* Create metadata root */
	root = xmlNewDocNode (doc, NULL, (const xmlChar *)"metadata", NULL);
	xmlDocSetRootElement (doc, root);

    	g_hash_table_foreach (xedit_metadata_manager->items,
			      (GHFunc)save_item,
			      root);        

	/* FIXME: lock file - Paolo */
	file_name = get_metadata_filename ();
	if (file_name != NULL)
	{
		gchar *cache_dir;
		int res;

		/* make sure the cache dir exists */
		cache_dir = xedit_dirs_get_user_cache_dir ();
		res = g_mkdir_with_parents (cache_dir, 0755);
		if (res != -1)
		{
			xmlSaveFormatFile (file_name, doc, 1);
		}

		g_free (cache_dir);
		g_free (file_name);
	}

	xmlFreeDoc (doc); 

	xedit_debug_message (DEBUG_METADATA, "DONE");

	return FALSE;
}