CalBackendClass now is just an interface for calendar backends; this is an

2000-05-08  Federico Mena Quintero  <federico@helixcode.com>

	* pcs/cal-backend.h (CalBackendClass): CalBackendClass now is just
	an interface for calendar backends; this is an abstract class.
	Put in the vtable for the backend methods.

	* pcs/cal-backend.c (cal_backend_new): Removed function, since
	CalBackend is not just an abstract class.
	Removed implementation-specific functions and made public
	functions call the virtual methods instead.

	* pcs/cal-backend-imc.[ch]: New files with the CalBackendIMC
	implementation; this implements a backend for iCalendar and
	vCalendar files.  Moved the implementation-specific stuff from
	cal-backend.[ch] to here.

	* pcs/cal-backend-imc.c (CalendarFormat): Moved enumeration to
	here.  Added a CAL_UNKNOWN value for when the backend is not
	loaded yet.
	(cal_backend_imc_init): Initialize priv->format as CAL_UNKNOWN.
	(save_to_vcal): Use the same VCProdIdProp value as in
	cal-util/calobj.c.  Use "1.0" as the VCVersionProp as per the
	vCalendar spec.
	(ensure_uid): Return nothing, since the result value need not be
	used anymore.
	(add_object): Since we mark the calendar as dirty anyways, we do
	not need to check the result value of ensure_uid() anymore.
	(remove_object): Asssert that we know how to handle the object's
	type.  We do this in add_object() anyways.

	* pcs/Makefile.am (libpcs_a_SOURCES): Added cal-backend-imc.[ch].

	* gui/gnome-cal.c: Replaced debugging printf()s with g_message()
	so that we can see the line number where they occur.

	* gui/gnome-cal.c (gnome_calendar_load_cb): Sort of handle the
	LOAD_METHOD_NOT_SUPPORTED result code, and added a default for the
	switch.

	* cal-client/cal-listener.h (CalListenerLoadStatus): Removed
	enumeration; it is stupid to translate all values for the
	CalClient when it is going to translate them again.
	(CalListenerClass::cal_loaded): This signal now passes the
	LoadStatus directly from the CORBA side.

	* cal-client/cal-listener.c (Listener_cal_loaded): Do not
	translate the status value.

	* cal-client/cal-client.h (CalClientLoadStatus): Added the
	CAL_CLIENT_LOAD_METHOD_NOT_SUPPORTED error code.

	* cal-client/cal-client.c (cal_loaded_cb): Translate the CORBA
	version of the LoadStatus result code.

	* pcs/cal-factory.c (CalFactoryPrivate): New methods field for the
	hash table from method strings to the GtkTypes for backend class
	types.
	(cal_factory_init): Create the priv->methods hash table.
	(cal_factory_destroy): Free the priv->methods hash table.
	(cal_factory_register_method): New function to register a backend
	class for a particular URI method.
	(launch_backend_for_uri): New function to launch a backend for a
	particular URI's method.
	(load_backend): Use launch_backend_for_uri().  Move the error
	notification code from load_fn() to here.
	(create_backend): Use launch_backend_for_uri().  Move the error
	notification code form create_fn() to here; it is #ifdefed out
	since currently cal_backend_create() does not have any error
	reporting capabilities.

	* idl/evolution-calendar.idl (Listener::LoadStatus): Added a
	PROTOCOL_NOT_SUPPORTED error code.

	* pcs/cal-factory.c (cal_factory_load cal_factory_create): Removed
	functions, since they were supposed to be internal only.
	(CalFactory_load): Call queue_load_create_job() directly.
	(CalFactory_create): Likewise.

svn path=/trunk/; revision=2921

1 files changed, 38 insertions, 895 deletions

diff --git a/calendar/pcs/cal-backend.c b/calendar/pcs/cal-backend.c
index 3aed2a41fa..27cc3e53ce 100644
--- a/calendar/pcs/cal-backend.c
+++ b/calendar/pcs/cal-backend.c
@@ -1,5 +1,5 @@
 /* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
-/* Evolution calendar backend
+/* Evolution calendar - generic backend class
  *
  * Copyright (C) 2000 Helix Code, Inc.
  *
@@ -25,39 +25,6 @@
 #include <cal-util/calobj.h>
 #include "cal-backend.h"
 #include "libversit/vcc.h"
-#include "icalendar.h"
-
-
-
-
-/* Private part of the CalBackend structure */
-typedef struct {
-	/* URI where the calendar data is stored */
-	GnomeVFSURI *uri;
-
-        /* format of this calendar (ical or vcal) */
-	CalendarFormat format;
-
-	/* List of Cal objects with their listeners */
-	GList *clients;
-
-	/* All the iCalObject structures in the calendar, hashed by UID.  The
-	 * hash key *is* icalobj->uid; it is not copied, so don't free it when
-	 * you remove an object from the hash table.
-	 */
-	GHashTable *object_hash;
-
-	/* All events, TODOs, and journals in the calendar */
-	GList *events;
-	GList *todos;
-	GList *journals;
-
-	/* Whether a calendar has been loaded */
-	guint loaded : 1;
-
-	/* Do we need to sync to permanent storage? */
-	gboolean dirty : 1;
-} CalBackendPrivate;
 
 
 
@@ -68,13 +35,13 @@ enum {
 };
 
 static void cal_backend_class_init (CalBackendClass *class);
-static void cal_backend_init (CalBackend *backend);
-static void cal_backend_destroy (GtkObject *object);
 
 static GtkObjectClass *parent_class;
 
 static guint cal_backend_signals[LAST_SIGNAL];
 
+#define CLASS(backend) (CAL_BACKEND_CLASS (GTK_OBJECT (backend)->klass))
+
 
 
 /**
@@ -97,7 +64,7 @@ cal_backend_get_type (void)
 			sizeof (CalBackend),
 			sizeof (CalBackendClass),
 			(GtkClassInitFunc) cal_backend_class_init,
-			(GtkObjectInitFunc) cal_backend_init,
+			(GtkObjectInitFunc) NULL,
 			NULL, /* reserved_1 */
 			NULL, /* reserved_2 */
 			(GtkClassInitFunc) NULL
@@ -129,391 +96,11 @@ cal_backend_class_init (CalBackendClass *class)
 				GTK_TYPE_NONE, 0);
 
 	gtk_object_class_add_signals (object_class, cal_backend_signals, LAST_SIGNAL);
-
-	object_class->destroy = cal_backend_destroy;
-}
-
-/* Object initialization function for the calendar backend */
-static void
-cal_backend_init (CalBackend *backend)
-{
-	CalBackendPrivate *priv;
-
-	priv = g_new0 (CalBackendPrivate, 1);
-	backend->priv = priv;
-
-	/* FIXME can be CAL_VCAL or CAL_ICAL */
-	priv->format = CAL_VCAL;
-}
-
-static void
-save_to_vcal (CalBackend *backend, char *fname)
-{
-	FILE *fp;
-	CalBackendPrivate *priv = backend->priv;
-	VObject *vcal;
-	GList *l;
-
-	if (g_file_exists (fname)){
-		char *backup_name = g_strconcat (fname, "~", NULL);
-
-		if (g_file_exists (backup_name)){
-			unlink (backup_name);
-		}
-		rename (fname, backup_name);
-		g_free (backup_name);
-	}
-
-	vcal = newVObject (VCCalProp);
-	addPropValue (vcal, VCProdIdProp,
-		      "-//GNOME//NONSGML GnomeCalendar//EN");
-	addPropValue (vcal, VCVersionProp, VERSION);
-
-	for (l = priv->events; l; l = l->next) {
-		iCalObject *ical = l->data;
-		VObject *vobject = ical_object_to_vobject (ical);
-		addVObjectProp (vcal, vobject);
-	}
-	for (l = priv->todos; l; l = l->next) {
-		iCalObject *ical = l->data;
-		VObject *vobject = ical_object_to_vobject (ical);
-		addVObjectProp (vcal, vobject);
-	}
-	for (l = priv->journals; l; l = l->next) {
-		iCalObject *ical = l->data;
-		VObject *vobject = ical_object_to_vobject (ical);
-		addVObjectProp (vcal, vobject);
-	}
-
-	fp = fopen(fname,"w");
-	if (fp) {
-		writeVObject(fp, vcal);
-		fclose(fp);
-	}
-	cleanVObject (vcal);
-	cleanStrTbl ();
-}
-
-/* Saves a calendar */
-static void
-save (CalBackend *backend)
-{
-	char *str_uri;
-	CalBackendPrivate *priv = backend->priv;
-
-	str_uri = gnome_vfs_uri_to_string (priv->uri,
-				   (GNOME_VFS_URI_HIDE_USER_NAME
-				    | GNOME_VFS_URI_HIDE_PASSWORD
-				    | GNOME_VFS_URI_HIDE_HOST_NAME
-				    | GNOME_VFS_URI_HIDE_HOST_PORT
-				    | GNOME_VFS_URI_HIDE_TOPLEVEL_METHOD));
-
-	if (! priv->dirty){
-		return;
-	}
-
-	switch (priv->format) {
-	case CAL_VCAL:
-		save_to_vcal (backend, str_uri);
-		break;
-	case CAL_ICAL:
-		/*icalendar_calendar_save (backend, str_uri);*/
-		/* FIX ME */
-		break;
-	default:
-		/* FIX ME log */
-	        break;
-	}
-
-	printf ("cal-backend: '%s' saved\n", str_uri);
-
-	g_free (str_uri);
-}
-
-
-/* g_hash_table_foreach() callback to destroy an iCalObject */
-static void
-free_ical_object (gpointer key, gpointer value, gpointer data)
-{
-	iCalObject *ico;
-
-	ico = value;
-	ical_object_destroy (ico);
-}
-
-/* Destroys a backend's data */
-static void
-destroy (CalBackend *backend)
-{
-	CalBackendPrivate *priv;
-
-	priv = backend->priv;
-
-	if (priv->uri) {
-		gnome_vfs_uri_unref (priv->uri);
-		priv->uri = NULL;
-	}
-
-	g_assert (priv->clients == NULL);
-
-	if (priv->object_hash) {
-		g_hash_table_foreach (priv->object_hash, free_ical_object, NULL);
-		g_hash_table_destroy (priv->object_hash);
-		priv->object_hash = NULL;
-	}
-
-	g_list_free (priv->events);
-	g_list_free (priv->todos);
-	g_list_free (priv->journals);
-
-	priv->events = NULL;
-	priv->todos = NULL;
-	priv->journals = NULL;
-
-	priv->loaded = FALSE;
-}
-
-/* Destroy handler for the calendar backend */
-static void
-cal_backend_destroy (GtkObject *object)
-{
-	CalBackend *backend;
-	CalBackendPrivate *priv;
-
-	g_return_if_fail (object != NULL);
-	g_return_if_fail (IS_CAL_BACKEND (object));
-
-	backend = CAL_BACKEND (object);
-	priv = backend->priv;
-
-	/*
-	if (priv->loaded)
-		save (backend);
-	*/
-
-	destroy (backend);
-
-	g_free (priv);
-
-	if (GTK_OBJECT_CLASS (parent_class)->destroy)
-		(* GTK_OBJECT_CLASS (parent_class)->destroy) (object);
-}
-
-
-
-/* iCalObject manipulation functions */
-
-/* Looks up an object by its UID in the backend's object hash table */
-static iCalObject *
-lookup_object (CalBackend *backend, const char *uid)
-{
-	CalBackendPrivate *priv;
-	iCalObject *ico;
-
-	priv = backend->priv;
-	ico = g_hash_table_lookup (priv->object_hash, uid);
-
-	return ico;
-}
-
-/* Ensures that an iCalObject has a unique identifier.  If it doesn't have one,
- * it will create one for it.  Returns whether an UID was created or not.
- */
-static gboolean
-ensure_uid (iCalObject *ico)
-{
-	char *buf;
-	gulong str_time;
-	static guint seqno = 0;
-
-	if (ico->uid){
-		return FALSE;
-	}
-
-	str_time = (gulong) time (NULL);
-
-	/* Is this good enough? */
-
-	buf = g_strdup_printf ("Evolution-Tlacuache-%d-%ld-%u",
-			       (int) getpid(), str_time, seqno++);
-	ico->uid = buf;
-	return TRUE;
-}
-
-/* Adds an object to the calendar backend.  Does *not* perform notification to
- * calendar clients.
- */
-static void
-add_object (CalBackend *backend, iCalObject *ico)
-{
-	CalBackendPrivate *priv;
-
-	g_assert (ico != NULL);
-	priv = backend->priv;
-
-#if 0
-	/* FIXME: gnomecal old code */
-	ico->new = 0;
-#endif
-
-	if (ensure_uid (ico))
-		/* FIXME: mark the calendar as dirty so that we can re-save it
-		 * with the object's new UID.
-		 */
-		;
-
-	g_hash_table_insert (priv->object_hash, ico->uid, ico);
-
-	priv->dirty = TRUE;
-
-	switch (ico->type) {
-	case ICAL_EVENT:
-		priv->events = g_list_prepend (priv->events, ico);
-#if 0
-		/* FIXME: gnomecal old code */
-		ical_object_try_alarms (ico);
-#  ifdef DEBUGGING_MAIL_ALARM
-		ico->malarm.trigger = 0;
-		calendar_notify (0, ico);
-#  endif
-#endif
-		break;
-
-	case ICAL_TODO:
-		priv->todos = g_list_prepend (priv->todos, ico);
-		break;
-
-	case ICAL_JOURNAL:
-		priv->journals = g_list_prepend (priv->journals, ico);
-		break;
-
-	default:
-		g_assert_not_reached ();
-	}
-
-#if 0
-	/* FIXME: gnomecal old code */
-	ico->last_mod = time (NULL);
-#endif
-}
-
-/* Removes an object from the backend's hash and lists.  Does not perform
- * notification on the clients.
- */
-static void
-remove_object (CalBackend *backend, iCalObject *ico)
-{
-	CalBackendPrivate *priv;
-	GList **list, *l;
-
-	priv = backend->priv;
-
-	g_assert (ico->uid != NULL);
-	g_hash_table_remove (priv->object_hash, ico->uid);
-
-	priv->dirty = TRUE;
-
-	switch (ico->type) {
-	case ICAL_EVENT:
-		list = &priv->events;
-		break;
-
-	case ICAL_TODO:
-		list = &priv->todos;
-		break;
-
-	case ICAL_JOURNAL:
-		list = &priv->journals;
-		break;
-
-	default:
-		list = NULL;
-	}
-
-	if (!list){
-		return;
-	}
-
-	l = g_list_find (*list, ico);
-	g_assert (l != NULL);
-
-	*list = g_list_remove_link (*list, l);
-	g_list_free_1 (l);
-
-	ical_object_destroy (ico);
-}
-
-/* Load a calendar from a VObject */
-static void
-load_from_vobject (CalBackend *backend, VObject *vobject)
-{
-	CalBackendPrivate *priv;
-	VObjectIterator i;
-
-	priv = backend->priv;
-
-	g_assert (!priv->loaded);
-	g_assert (priv->object_hash == NULL);
-	priv->object_hash = g_hash_table_new (g_str_hash, g_str_equal);
-
-	initPropIterator (&i, vobject);
-
-	while (moreIteration (&i)) {
-		VObject *this;
-		iCalObject *ical;
-		const char *object_name;
-
-		this = nextVObject (&i);
-		object_name = vObjectName (this);
-#if 0
-		/* FIXME?  What is this used for in gnomecal? */
-		if (strcmp (object_name, VCDCreatedProp) == 0) {
-			cal->created = time_from_isodate (str_val (this));
-			continue;
-		}
-#endif
-		if (strcmp (object_name, VCLocationProp) == 0)
-			continue; /* FIXME: imlement */
-
-		if (strcmp (object_name, VCProdIdProp) == 0)
-			continue; /* FIXME: implement */
-
-		if (strcmp (object_name, VCVersionProp) == 0)
-			continue; /* FIXME: implement */
-
-		if (strcmp (object_name, VCTimeZoneProp) == 0)
-			continue; /* FIXME: implement */
-
-		ical = ical_object_create_from_vobject (this, object_name);
-
-		/* FIXME: some broken files may have duplicated UIDs.  This is
-		 * Bad(tm).  Deal with it by creating new UIDs for them and
-		 * spitting some messages to the console.
-		 */
-
-		if (ical)
-			add_object (backend, ical);
-	}
 }
 
 
 
 /**
- * cal_backend_new:
- * @void:
- *
- * Creates a new empty calendar backend.  A calendar must then be loaded or
- * created before the backend can be used.
- *
- * Return value: A newly-created calendar backend.
- **/
-CalBackend *
-cal_backend_new (void)
-{
-	return CAL_BACKEND (gtk_type_new (CAL_BACKEND_TYPE));
-}
-
-/**
  * cal_backend_get_uri:
  * @backend: A calendar backend.
  *
@@ -525,54 +112,11 @@ cal_backend_new (void)
 GnomeVFSURI *
 cal_backend_get_uri (CalBackend *backend)
 {
-	CalBackendPrivate *priv;
-
 	g_return_val_if_fail (backend != NULL, NULL);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
 
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, NULL);
-	g_assert (priv->uri != NULL);
-
-	return priv->uri;
-}
-
-/* Callback used when a Cal is destroyed */
-static void
-cal_destroy_cb (GtkObject *object, gpointer data)
-{
-	Cal *cal;
-	Cal *lcal;
-	CalBackend *backend;
-	CalBackendPrivate *priv;
-	GList *l;
-
-	cal = CAL (object);
-
-	backend = CAL_BACKEND (data);
-	priv = backend->priv;
-
-	/* Find the cal in the list of clients */
-
-	for (l = priv->clients; l; l = l->next) {
-		lcal = CAL (l->data);
-
-		if (lcal == cal)
-			break;
-	}
-
-	g_assert (l != NULL);
-
-	/* Disconnect */
-
-	priv->clients = g_list_remove_link (priv->clients, l);
-	g_list_free_1 (l);
-
-	/* When all clients go away, notify the parent factory about it so that
-	 * it may decide whether to kill the backend or not.
-	 */
-	if (!priv->clients)
-		gtk_signal_emit (GTK_OBJECT (backend), cal_backend_signals[LAST_CLIENT_GONE]);
+	g_assert (CLASS (backend)->get_uri != NULL);
+	return (* CLASS (backend)->get_uri) (backend);
 }
 
 /**
@@ -586,143 +130,13 @@ cal_destroy_cb (GtkObject *object, gpointer data)
 void
 cal_backend_add_cal (CalBackend *backend, Cal *cal)
 {
-	CalBackendPrivate *priv;
-
 	g_return_if_fail (backend != NULL);
 	g_return_if_fail (IS_CAL_BACKEND (backend));
 
-	priv = backend->priv;
-	g_return_if_fail (priv->loaded);
-
-	g_return_if_fail (cal != NULL);
-	g_return_if_fail (IS_CAL (cal));
-
-	/* We do not keep a reference to the Cal since the calendar user agent
-	 * owns it.
-	 */
-
-	gtk_signal_connect (GTK_OBJECT (cal), "destroy",
-			    GTK_SIGNAL_FUNC (cal_destroy_cb),
-			    backend);
-
-	priv->clients = g_list_prepend (priv->clients, cal);
-}
-
-
-static icalcomponent* 
-icalendar_parse_file (char* fname)
-{
-	FILE* fp;
-	icalcomponent* comp = NULL;
-	gchar* str;
-	struct stat st;
-	int n;
-
-	fp = fopen (fname, "r");
-	if (!fp) {
-		g_warning ("Cannot open open calendar file.");
-		return NULL;
-	}
-	
-	stat (fname, &st);
-	
-	str = g_malloc (st.st_size + 2);
-	
-	n = fread ((gchar*) str, 1, st.st_size, fp);
-	if (n != st.st_size) {
-		g_warning ("Read error.");
-	}
-	str[n] = '\0';
-
-	fclose (fp);
-	
-	comp = icalparser_parse_string (str);
-	g_free (str);
-
-	return comp;
-}
-
-
-static void
-icalendar_calendar_load (CalBackend * cal, char* fname)
-{
-	CalBackendPrivate *priv;
-	icalcomponent *comp;
-	icalcomponent *subcomp;
-	iCalObject    *ical;
-
-	g_assert (cal);
-
-	priv = cal->priv;
-
-	g_assert (!priv->loaded);
-	g_assert (priv->object_hash == NULL);
-
-	priv->object_hash = g_hash_table_new (g_str_hash, g_str_equal);
-
-	comp = icalendar_parse_file (fname);
-	subcomp = icalcomponent_get_first_component (comp,
-						     ICAL_ANY_COMPONENT);
-	while (subcomp) {
-		ical = ical_object_create_from_icalcomponent (subcomp);
-		if (ical->type != ICAL_EVENT && 
-		    ical->type != ICAL_TODO  &&
-		    ical->type != ICAL_JOURNAL) {
-		       g_warning ("Skipping unsupported iCalendar component.");
-		} else
-			add_object (cal, ical);
-		subcomp = icalcomponent_get_next_component (comp,
-							   ICAL_ANY_COMPONENT);
-	}
+	g_assert (CLASS (backend)->add_cal != NULL);
+	return (* CLASS (backend)->add_cal) (backend, cal);
 }
 
-
-/*
-ics is to be used to designate a file containing (an arbitrary set of)
-calendaring and scheduling information.
-
-ifb is to be used to designate a file containing free or busy time
-information.
-
-anything else is assumed to be a vcal file.
-*/
-
-static CalendarFormat
-cal_get_type_from_filename (char *str_uri)
-{
-	int len;
-
-	if (str_uri == NULL)
-		return CAL_VCAL;
-
-	len = strlen (str_uri);
-	if (len < 4)
-		return CAL_VCAL;
-
-	if (str_uri[ len-4 ] == '.' && str_uri[ len-3 ] == 'i' &&
-	    str_uri[ len-2 ] == 'c' && str_uri[ len-1 ] == 's')
-		return CAL_ICAL;
-
-	if (str_uri[ len-4 ] == '.' && str_uri[ len-3 ] == 'i' &&
-	    str_uri[ len-2 ] == 'f' && str_uri[ len-1 ] == 'b')
-		return CAL_ICAL;
-
-	if (str_uri[ len-4 ] == '.' && str_uri[ len-3 ] == 'i' &&
-	    str_uri[ len-2 ] == 'c' && str_uri[ len-1 ] == 's')
-		return CAL_ICAL;
-
-	if (len < 5)
-		return CAL_VCAL;
-
-	if (str_uri[ len-5 ] == '.' && str_uri[ len-4 ] == 'i' &&
-	    str_uri[ len-3 ] == 'c' && str_uri[ len-2 ] == 'a' &&
-	    str_uri[ len-1 ] == 'l')
-		return CAL_ICAL;
-
-	return CAL_VCAL;
-}
-
-
 /**
  * cal_backend_load:
  * @backend: A calendar backend.
@@ -736,66 +150,12 @@ cal_get_type_from_filename (char *str_uri)
 CalBackendLoadStatus
 cal_backend_load (CalBackend *backend, GnomeVFSURI *uri)
 {
-	CalBackendPrivate *priv;
-	VObject *vobject;
-	char *str_uri;
-
 	g_return_val_if_fail (backend != NULL, CAL_BACKEND_LOAD_ERROR);
-	g_return_val_if_fail (IS_CAL_BACKEND (backend),CAL_BACKEND_LOAD_ERROR);
-
-	priv = backend->priv;
-	g_return_val_if_fail (!priv->loaded, CAL_BACKEND_LOAD_ERROR);
-
+	g_return_val_if_fail (IS_CAL_BACKEND (backend), CAL_BACKEND_LOAD_ERROR);
 	g_return_val_if_fail (uri != NULL, CAL_BACKEND_LOAD_ERROR);
 
-	/* FIXME: this looks rather bad; maybe we should check for local files
-	 * and fail if they are remote.
-	 */
-
-	str_uri = gnome_vfs_uri_to_string (uri,
-				   (GNOME_VFS_URI_HIDE_USER_NAME
-				    | GNOME_VFS_URI_HIDE_PASSWORD
-				    | GNOME_VFS_URI_HIDE_HOST_NAME
-				    | GNOME_VFS_URI_HIDE_HOST_PORT
-				    | GNOME_VFS_URI_HIDE_TOPLEVEL_METHOD));
-
-
-	/* look at the extension on the filename and decide
-	   if this is a ical or vcal file */
-
-	priv->format = cal_get_type_from_filename (str_uri);
-
-	/* load */
-
-	switch (priv->format) {
-	case CAL_VCAL:
-	        vobject = Parse_MIME_FromFileName (str_uri);
-	
-		if (!vobject){
-			g_free (str_uri);
-			return CAL_BACKEND_LOAD_ERROR;
-		}
-	
-		load_from_vobject (backend, vobject);
-		cleanVObject (vobject);
-		cleanStrTbl ();
-		break;
-	case CAL_ICAL:
-		icalendar_calendar_load (backend, str_uri);
-		break;
-	default:
-		g_free (str_uri);
-	        return CAL_BACKEND_LOAD_ERROR;
-	}
-
-	g_free (str_uri);
-
-	gnome_vfs_uri_ref (uri);
-
-	priv->uri = uri;
-	priv->loaded = TRUE;
-
-	return CAL_BACKEND_LOAD_SUCCESS;
+	g_assert (CLASS (backend)->load != NULL);
+	return (* CLASS (backend)->load) (backend, uri);
 }
 
 /**
@@ -808,31 +168,12 @@ cal_backend_load (CalBackend *backend, GnomeVFSURI *uri)
 void
 cal_backend_create (CalBackend *backend, GnomeVFSURI *uri)
 {
-	CalBackendPrivate *priv;
-
 	g_return_if_fail (backend != NULL);
 	g_return_if_fail (IS_CAL_BACKEND (backend));
-
-	priv = backend->priv;
-	g_return_if_fail (!priv->loaded);
-
 	g_return_if_fail (uri != NULL);
 
-	/* Create the new calendar information */
-
-	g_assert (priv->object_hash == NULL);
-	priv->object_hash = g_hash_table_new (g_str_hash, g_str_equal);
-
-	priv->dirty = TRUE;
-
-	/* Done */
-
-	gnome_vfs_uri_ref (uri);
-
-	priv->uri = uri;
-	priv->loaded = TRUE;
-
-	save (backend);
+	g_assert (CLASS (backend)->create != NULL);
+	(* CLASS (backend)->create) (backend, uri);
 }
 
 /**
@@ -850,66 +191,12 @@ cal_backend_create (CalBackend *backend, GnomeVFSURI *uri)
 char *
 cal_backend_get_object (CalBackend *backend, const char *uid)
 {
-	CalBackendPrivate *priv;
-	iCalObject *ico;
-	char *buf;
-
 	g_return_val_if_fail (backend != NULL, NULL);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
-
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, NULL);
-
 	g_return_val_if_fail (uid != NULL, NULL);
 
-	g_assert (priv->object_hash != NULL);
-
-	ico = lookup_object (backend, uid);
-
-	if (!ico){
-		return NULL;
-	}
-
-	buf = ical_object_to_string (ico);
-
-	return buf;
-}
-
-struct get_uids_closure {
-	CalObjType type;
-	GList *uid_list;
-};
-
-/* Builds a list of UIDs for objects that match the sought type.  Called from
- * g_hash_table_foreach().
- */
-static void
-build_uids_list (gpointer key, gpointer value, gpointer data)
-{
-	iCalObject *ico;
-	struct get_uids_closure *c;
-	gboolean store;
-
-	ico = value;
-	c = data;
-
-	store = FALSE;
-
-	/*
-	if (c->type & CALOBJ_TYPE_ANY)
-		store = TRUE;
-	else */
-	if (ico->type == ICAL_EVENT)
-		store = (c->type & CALOBJ_TYPE_EVENT) ? TRUE : FALSE;
-	else if (ico->type == ICAL_TODO)
-		store = (c->type & CALOBJ_TYPE_TODO) ? TRUE : FALSE;
-	else if (ico->type == ICAL_JOURNAL)
-		store = (c->type & CALOBJ_TYPE_JOURNAL) ? TRUE : FALSE;
-	else
-		store = (c->type & CALOBJ_TYPE_OTHER) ? TRUE : FALSE;
-
-	if (store)
-		c->uid_list = g_list_prepend (c->uid_list, g_strdup (ico->uid));
+	g_assert (CLASS (backend)->get_object != NULL);
+	return (* CLASS (backend)->get_object) (backend, uid);
 }
 
 /**
@@ -925,68 +212,11 @@ build_uids_list (gpointer key, gpointer value, gpointer data)
 GList *
 cal_backend_get_uids (CalBackend *backend, CalObjType type)
 {
-	CalBackendPrivate *priv;
-	struct get_uids_closure c;
-
 	g_return_val_if_fail (backend != NULL, NULL);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
 
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, NULL);
-
-	/* We go through the hash table instead of the lists of particular
-	 * object types so that we can pick up CALOBJ_TYPE_OTHER objects.
-	 */
-
-	c.type = type;
-	c.uid_list = NULL;
-	g_hash_table_foreach (priv->object_hash, build_uids_list, &c);
-
-	return c.uid_list;
-}
-
-struct build_event_list_closure {
-	CalBackend *backend;
-	GList *event_list;
-};
-
-/* Builds a sorted list of event object instances.  Used as a callback from
- * ical_object_generate_events().
- */
-static int
-build_event_list (iCalObject *ico, time_t start, time_t end, void *data)
-{
-	CalObjInstance *icoi;
-	struct build_event_list_closure *c;
-
-	c = data;
-
-	icoi = g_new (CalObjInstance, 1);
-
-	g_assert (ico->uid != NULL);
-	icoi->uid = g_strdup (ico->uid);
-	icoi->start = start;
-	icoi->end = end;
-
-	c->event_list = g_list_prepend (c->event_list, icoi);
-
-	return TRUE;
-}
-
-/* Compares two CalObjInstance structures by their start times.  Called from
- * g_list_sort().
- */
-static gint
-compare_instance_func (gconstpointer a, gconstpointer b)
-{
-	const CalObjInstance *ca, *cb;
-	time_t diff;
-
-	ca = a;
-	cb = b;
-
-	diff = ca->start - cb->start;
-	return (diff < 0) ? -1 : (diff > 0) ? 1 : 0;
+	g_assert (CLASS (backend)->get_uids != NULL);
+	return (* CLASS (backend)->get_uids) (backend, type);
 }
 
 /**
@@ -1005,67 +235,13 @@ compare_instance_func (gconstpointer a, gconstpointer b)
 GList *
 cal_backend_get_events_in_range (CalBackend *backend, time_t start, time_t end)
 {
-	CalBackendPrivate *priv;
-	struct build_event_list_closure c;
-	GList *l;
-
 	g_return_val_if_fail (backend != NULL, NULL);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
-
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, NULL);
-
 	g_return_val_if_fail (start != -1 && end != -1, NULL);
 	g_return_val_if_fail (start <= end, NULL);
 
-	c.backend = backend;
-	c.event_list = NULL;
-
-	for (l = priv->events; l; l = l->next) {
-		iCalObject *ico;
-
-		ico = l->data;
-		ical_object_generate_events (ico, start, end,
-					     build_event_list, &c);
-	}
-
-	c.event_list = g_list_sort (c.event_list, compare_instance_func);
-
-	return c.event_list;
-}
-
-/* Notifies a backend's clients that an object was updated */
-static void
-notify_update (CalBackend *backend, const char *uid)
-{
-	CalBackendPrivate *priv;
-	GList *l;
-
-	priv = backend->priv;
-
-	for (l = priv->clients; l; l = l->next) {
-		Cal *cal;
-
-		cal = CAL (l->data);
-		cal_notify_update (cal, uid);
-	}
-}
-
-/* Notifies a backend's clients that an object was removed */
-static void
-notify_remove (CalBackend *backend, const char *uid)
-{
-	CalBackendPrivate *priv;
-	GList *l;
-
-	priv = backend->priv;
-
-	for (l = priv->clients; l; l = l->next) {
-		Cal *cal;
-
-		cal = CAL (l->data);
-		cal_notify_remove (cal, uid);
-	}
+	g_assert (CLASS (backend)->get_events_in_range != NULL);
+	return (* CLASS (backend)->get_events_in_range) (backend, start, end);
 }
 
 /**
@@ -1081,45 +257,15 @@ notify_remove (CalBackend *backend, const char *uid)
  * Return value: TRUE on success, FALSE on being passed an invalid object.
  **/
 gboolean
-cal_backend_update_object (CalBackend *backend, const char *uid,
-			   const char *calobj)
+cal_backend_update_object (CalBackend *backend, const char *uid, const char *calobj)
 {
-	CalBackendPrivate *priv;
-	iCalObject *ico, *new_ico;
-	CalObjFindStatus status;
-
 	g_return_val_if_fail (backend != NULL, FALSE);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), FALSE);
-
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, FALSE);
-	
 	g_return_val_if_fail (uid != NULL, FALSE);
 	g_return_val_if_fail (calobj != NULL, FALSE);
 
-	/* Pull the object from the string */
-
-	status = ical_object_find_in_string (uid, calobj, &new_ico);
-
-	if (status != CAL_OBJ_FIND_SUCCESS){
-		return FALSE;
-	}
-
-	/* Update the object */
-
-	ico = lookup_object (backend, uid);
-
-	if (ico)
-		remove_object (backend, ico);
-
-	add_object (backend, new_ico);
-	save (backend);
-
-	/* FIXME: do the notification asynchronously */
-
-	notify_update (backend, new_ico->uid);
-
-	return TRUE;
+	g_assert (CLASS (backend)->update_object != NULL);
+	return (* CLASS (backend)->update_object) (backend, uid, calobj);
 }
 
 /**
@@ -1136,29 +282,26 @@ cal_backend_update_object (CalBackend *backend, const char *uid,
 gboolean
 cal_backend_remove_object (CalBackend *backend, const char *uid)
 {
-	CalBackendPrivate *priv;
-	iCalObject *ico;
-
 	g_return_val_if_fail (backend != NULL, FALSE);
 	g_return_val_if_fail (IS_CAL_BACKEND (backend), FALSE);
-
-	priv = backend->priv;
-	g_return_val_if_fail (priv->loaded, FALSE);
-	
 	g_return_val_if_fail (uid != NULL, FALSE);
 
-	ico = lookup_object (backend, uid);
-	if (!ico){
-		return FALSE;
-	}
-
-	remove_object (backend, ico);
-
-	priv->dirty = TRUE;
-	save (backend);
+	g_assert (CLASS (backend)->remove_object != NULL);
+	return (* CLASS (backend)->remove_object) (backend, uid);
+}
 
-	/* FIXME: do the notification asynchronously */
-	notify_remove (backend, uid);
+/**
+ * cal_backend_last_client_gone:
+ * @backend: A calendar backend.
+ * 
+ * Emits the "last_client_gone" signal of a calendar backend.  This function is
+ * to be used only by backend implementations.
+ **/
+void
+cal_backend_last_client_gone (CalBackend *backend)
+{
+	g_return_if_fail (backend != NULL);
+	g_return_if_fail (IS_CAL_BACKEND (backend));
 
-	return TRUE;
+	gtk_signal_emit (GTK_OBJECT (backend), cal_backend_signals[LAST_CLIENT_GONE]);
 }