path: root/calendar/pcs/cal-backend.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/* Evolution calendar - generic backend class
 *
 * Copyright (C) 2000 Ximian, Inc.
 * Copyright (C) 2000 Ximian, Inc.
 *
 * Authors: Federico Mena-Quintero <federico@ximian.com>
 *          JP Rosevear <jpr@ximian.com>
 *          Rodrigo Moya <rodrigo@ximian.com>    
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */

#include <config.h>
#include <libxml/parser.h>
#include <libxml/parserInternals.h>
#include <libxml/xmlmemory.h>

#include "cal-backend.h"
#include "libversit/vcc.h"



/* A category that exists in some of the objects of the calendar */
typedef struct {
    /* Category name, also used as the key in the categories hash table */
    char *name;

    /* Number of objects that have this category */
    int refcount;
} CalBackendCategory;

/* Private part of the CalBackend structure */
struct _CalBackendPrivate {
    /* The uri for this backend */
    char *uri;

    /* The kind of components for this backend */
    icalcomponent_kind kind;
    
    /* List of Cal objects */
    GMutex *clients_mutex;
    GList *clients;

    GMutex *queries_mutex;
    EList *queries;
    
    /* Hash table of live categories, temporary hash of
     * added/removed categories, and idle handler for sending
     * category_changed.
     */
    GHashTable *categories;
    GHashTable *changed_categories;
    guint category_idle_id;
};

/* Property IDs */
enum props {
    PROP_0,
    PROP_URI,
    PROP_KIND
};

/* Signal IDs */
enum {
    LAST_CLIENT_GONE,
    OPENED,
    REMOVED,
    LAST_SIGNAL
};
static guint cal_backend_signals[LAST_SIGNAL];

static void cal_backend_class_init (CalBackendClass *class);
static void cal_backend_init (CalBackend *backend);
static void cal_backend_finalize (GObject *object);

static void notify_categories_changed (CalBackend *backend);

#define CLASS(backend) (CAL_BACKEND_CLASS (G_OBJECT_GET_CLASS (backend)))

static GObjectClass *parent_class;



/**
 * cal_backend_get_type:
 * @void:
 *
 * Registers the #CalBackend class if necessary, and returns the type ID
 * associated to it.
 *
 * Return value: The type ID of the #CalBackend class.
 **/
GType
cal_backend_get_type (void)
{
    static GType cal_backend_type = 0;

    if (!cal_backend_type) {
        static GTypeInfo info = {
                        sizeof (CalBackendClass),
                        (GBaseInitFunc) NULL,
                        (GBaseFinalizeFunc) NULL,
                        (GClassInitFunc) cal_backend_class_init,
                        NULL, NULL,
                        sizeof (CalBackend),
                        0,
                        (GInstanceInitFunc) cal_backend_init,
                };
        cal_backend_type = g_type_register_static (G_TYPE_OBJECT, "CalBackend", &info, 0);
    }

    return cal_backend_type;
}

static void
cal_backend_set_property (GObject *object, guint property_id, const GValue *value, GParamSpec *pspec)
{
    CalBackend *backend;
    CalBackendPrivate *priv;
    
    backend = CAL_BACKEND (object);
    priv = backend->priv;
    
    switch (property_id) {
    case PROP_URI:
        g_free (priv->uri);
        priv->uri = g_value_dup_string (value);
        break;
    case PROP_KIND:
        priv->kind = g_value_get_ulong (value);
        break;
    default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
        break;
    }
}

static void
cal_backend_get_property (GObject *object, guint property_id, GValue *value, GParamSpec *pspec)
{
    CalBackend *backend;
    CalBackendPrivate *priv;
    
    backend = CAL_BACKEND (object);
    priv = backend->priv;

    switch (property_id) {
    case PROP_URI:
        g_value_set_string (value, cal_backend_get_uri (backend));
        break;
    case PROP_KIND:
        g_value_set_ulong (value, cal_backend_get_kind (backend));
        break;
    default:
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
        break;
    }
}

/* Class initialization function for the calendar backend */
static void
cal_backend_class_init (CalBackendClass *class)
{
    GObjectClass *object_class;

    parent_class = (GObjectClass *) g_type_class_peek_parent (class);

    object_class = (GObjectClass *) class;

    object_class->set_property = cal_backend_set_property;
    object_class->get_property = cal_backend_get_property;
    object_class->finalize = cal_backend_finalize;

    g_object_class_install_property (object_class, PROP_URI, 
                     g_param_spec_string ("uri", NULL, NULL, "",
                                  G_PARAM_READABLE | G_PARAM_WRITABLE
                                  | G_PARAM_CONSTRUCT_ONLY));

    g_object_class_install_property (object_class, PROP_KIND, 
                     g_param_spec_ulong ("kind", NULL, NULL, 
                                 ICAL_NO_COMPONENT, ICAL_XLICMIMEPART_COMPONENT, 
                                 ICAL_NO_COMPONENT,
                                 G_PARAM_READABLE | G_PARAM_WRITABLE
                                 | G_PARAM_CONSTRUCT_ONLY));    
    cal_backend_signals[LAST_CLIENT_GONE] =
        g_signal_new ("last_client_gone",
                  G_TYPE_FROM_CLASS (class),
                  G_SIGNAL_RUN_FIRST,
                  G_STRUCT_OFFSET (CalBackendClass, last_client_gone),
                  NULL, NULL,
                  g_cclosure_marshal_VOID__VOID,
                  G_TYPE_NONE, 0);
    cal_backend_signals[OPENED] =
        g_signal_new ("opened",
                  G_TYPE_FROM_CLASS (class),
                  G_SIGNAL_RUN_FIRST,
                  G_STRUCT_OFFSET (CalBackendClass, opened),
                  NULL, NULL,
                  g_cclosure_marshal_VOID__ENUM,
                  G_TYPE_NONE, 1,
                  G_TYPE_INT);
    cal_backend_signals[REMOVED] =
        g_signal_new ("removed",
                  G_TYPE_FROM_CLASS (class),
                  G_SIGNAL_RUN_FIRST,
                  G_STRUCT_OFFSET (CalBackendClass, removed),
                  NULL, NULL,
                  g_cclosure_marshal_VOID__ENUM,
                  G_TYPE_NONE, 1,
                  G_TYPE_INT);

    class->last_client_gone = NULL;
    class->opened = NULL;
    class->obj_updated = NULL;

    class->get_cal_address = NULL;
    class->get_alarm_email_address = NULL;
    class->get_static_capabilities = NULL;
    class->open = NULL;
    class->is_loaded = NULL;
    class->is_read_only = NULL;
    class->start_query = NULL;
    class->get_mode = NULL;
    class->set_mode = NULL; 
    class->get_object = NULL;
    class->get_default_object = NULL;
    class->get_object_list = NULL;
    class->get_free_busy = NULL;
    class->get_changes = NULL;
    class->discard_alarm = NULL;
    class->create_object = NULL;
    class->modify_object = NULL;
    class->remove_object = NULL;
    class->receive_objects = NULL;
    class->send_objects = NULL;
    class->get_timezone = NULL;
    class->add_timezone = NULL;
    class->set_default_timezone = NULL;
}

/* Object initialization func for the calendar backend */
void
cal_backend_init (CalBackend *backend)
{
    CalBackendPrivate *priv;

    priv = g_new0 (CalBackendPrivate, 1);
    backend->priv = priv;

    priv->clients = NULL;
    priv->clients_mutex = g_mutex_new ();

    /* FIXME bonobo_object_ref/unref? */
    priv->queries = e_list_new((EListCopyFunc) g_object_ref, (EListFreeFunc) g_object_unref, NULL);
    priv->queries_mutex = g_mutex_new ();
    
    priv->categories = g_hash_table_new (g_str_hash, g_str_equal);
    priv->changed_categories = g_hash_table_new (g_str_hash, g_str_equal);
}

/* Used from g_hash_table_foreach(), frees a CalBackendCategory structure */
static void
free_category_cb (gpointer key, gpointer value, gpointer data)
{
    CalBackendCategory *c = value;

    g_free (c->name);
    g_free (c);
}

static gboolean
prune_changed_categories (gpointer key, gpointer value, gpointer data)
{
    CalBackendCategory *c = value;

    if (!c->refcount)
        free_category_cb (key, value, data);
    return TRUE;
}

void
cal_backend_finalize (GObject *object)
{
    CalBackend *backend = (CalBackend *)object;
    CalBackendPrivate *priv;

    priv = backend->priv;

    g_assert (priv->clients == NULL);

    g_object_unref (priv->queries);

    g_hash_table_foreach_remove (priv->changed_categories, prune_changed_categories, NULL);
    g_hash_table_destroy (priv->changed_categories);

    g_hash_table_foreach (priv->categories, free_category_cb, NULL);
    g_hash_table_destroy (priv->categories);

    g_mutex_free (priv->clients_mutex);
    g_mutex_free (priv->queries_mutex);

    if (priv->category_idle_id)
        g_source_remove (priv->category_idle_id);

    g_free (priv);

    G_OBJECT_CLASS (parent_class)->finalize (object);
}



/**
 * cal_backend_get_uri:
 * @backend: A calendar backend.
 *
 * Queries the URI of a calendar backend, which must already have an open
 * calendar.
 *
 * Return value: The URI where the calendar is stored.
 **/
const char *
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;
    
    return priv->uri;
}

icalcomponent_kind
cal_backend_get_kind (CalBackend *backend)
{
    CalBackendPrivate *priv;
    
    g_return_val_if_fail (backend != NULL, ICAL_NO_COMPONENT);
    g_return_val_if_fail (IS_CAL_BACKEND (backend), ICAL_NO_COMPONENT);

    priv = backend->priv;
    
    return priv->kind;
}

static void
cal_destroy_cb (gpointer data, GObject *where_cal_was)
{
    CalBackend *backend = CAL_BACKEND (data);

    cal_backend_remove_client (backend, (Cal *) where_cal_was);
}

static void
listener_died_cb (gpointer cnx, gpointer data)
{
    Cal *cal = CAL (data);

    cal_backend_remove_client (cal_get_backend (cal), cal);
}

static void
last_client_gone (CalBackend *backend)
{
    g_signal_emit (backend, cal_backend_signals[LAST_CLIENT_GONE], 0);
}

void
cal_backend_add_client (CalBackend *backend, Cal *cal)
{
    CalBackendPrivate *priv;
    
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (cal != NULL);
    g_return_if_fail (IS_CAL (cal));

    priv = backend->priv;
    
    bonobo_object_set_immortal (BONOBO_OBJECT (cal), TRUE);

    g_object_weak_ref (G_OBJECT (cal), cal_destroy_cb, backend);

    ORBit_small_listen_for_broken (cal_get_listener (cal), G_CALLBACK (listener_died_cb), cal);

    g_mutex_lock (priv->clients_mutex);
    priv->clients = g_list_append (priv->clients, cal);
    g_mutex_unlock (priv->clients_mutex);

    /* Tell the new client about the list of categories.
     * (Ends up telling all the other clients too, but *shrug*.)
     */
    /* FIXME This doesn't seem right at all */
    notify_categories_changed (backend);
}

void
cal_backend_remove_client (CalBackend *backend, Cal *cal)
{
    CalBackendPrivate *priv;
    
    /* XXX this needs a bit more thinking wrt the mutex - we
       should be holding it when we check to see if clients is
       NULL */
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (cal != NULL);
    g_return_if_fail (IS_CAL (cal));

    priv = backend->priv;

    /* Disconnect */
    g_mutex_lock (priv->clients_mutex);
    priv->clients = g_list_remove (priv->clients, cal);
    g_mutex_unlock (priv->clients_mutex);

    /* 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)
        last_client_gone (backend);
}

void
cal_backend_add_query (CalBackend *backend, Query *query)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_mutex_lock (backend->priv->queries_mutex);

    e_list_append (backend->priv->queries, query);
    
    g_mutex_unlock (backend->priv->queries_mutex);
}

EList *
cal_backend_get_queries (CalBackend *backend)
{
    g_return_val_if_fail (backend != NULL, NULL);
    g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);

    return g_object_ref (backend->priv->queries);
}


/**
 * cal_backend_get_cal_address:
 * @backend: A calendar backend.
 *
 * Queries the cal address associated with a calendar backend, which
 * must already have an open calendar.
 *
 * Return value: The cal address associated with the calendar.
 **/
void
cal_backend_get_cal_address (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_cal_address != NULL);
    (* CLASS (backend)->get_cal_address) (backend, cal);
}

void
cal_backend_get_alarm_email_address (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_alarm_email_address != NULL);
    (* CLASS (backend)->get_alarm_email_address) (backend, cal);
}

void
cal_backend_get_ldap_attribute (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_ldap_attribute != NULL);
    (* CLASS (backend)->get_ldap_attribute) (backend, cal);
}

void
cal_backend_get_static_capabilities (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_static_capabilities != NULL);
    (* CLASS (backend)->get_static_capabilities) (backend, cal);
}

/**
 * cal_backend_open:
 * @backend: A calendar backend.
 * @uristr: URI that contains the calendar data.
 * @only_if_exists: Whether the calendar should be opened only if it already
 * exists.  If FALSE, a new calendar will be created when the specified @uri
 * does not exist.
 *
 * Opens a calendar backend with data from a calendar stored at the specified
 * URI.
 *
 * Return value: An operation status code.
 **/
void
cal_backend_open (CalBackend *backend, Cal *cal, gboolean only_if_exists)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->open != NULL);
    (* CLASS (backend)->open) (backend, cal, only_if_exists);
}

void
cal_backend_remove (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->remove != NULL);
    (* CLASS (backend)->remove) (backend, cal);
}

/**
 * cal_backend_is_loaded:
 * @backend: A calendar backend.
 * 
 * Queries whether a calendar backend has been loaded yet.
 * 
 * Return value: TRUE if the backend has been loaded with data, FALSE
 * otherwise.
 **/
gboolean
cal_backend_is_loaded (CalBackend *backend)
{
    gboolean result;

    g_return_val_if_fail (backend != NULL, FALSE);
    g_return_val_if_fail (IS_CAL_BACKEND (backend), FALSE);

    g_assert (CLASS (backend)->is_loaded != NULL);
    result = (* CLASS (backend)->is_loaded) (backend);

    return result;
}

/**
 * cal_backend_is_read_only
 * @backend: A calendar backend.
 *
 * Queries whether a calendar backend is read only or not.
 *
 * Return value: TRUE if the calendar is read only, FALSE otherwise.
 */
void
cal_backend_is_read_only (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->is_read_only != NULL);
    (* CLASS (backend)->is_read_only) (backend, cal);
}

void 
cal_backend_start_query (CalBackend *backend, Query *query)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->start_query != NULL);
    (* CLASS (backend)->start_query) (backend, query);
}

/**
 * cal_backend_get_mode:
 * @backend: A calendar backend. 
 * 
 * Queries whether a calendar backend is connected remotely.
 * 
 * Return value: The current mode the calendar is in
 **/
CalMode
cal_backend_get_mode (CalBackend *backend)
{
    CalMode result;

    g_return_val_if_fail (backend != NULL, FALSE);
    g_return_val_if_fail (IS_CAL_BACKEND (backend), FALSE);

    g_assert (CLASS (backend)->get_mode != NULL);
    result = (* CLASS (backend)->get_mode) (backend);

    return result;
}


/**
 * cal_backend_set_mode:
 * @backend: A calendar backend
 * @mode: Mode to change to
 * 
 * Sets the mode of the calendar
 * 
 **/
void
cal_backend_set_mode (CalBackend *backend, CalMode mode)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->set_mode != NULL);
    (* CLASS (backend)->set_mode) (backend, mode);
}

void
cal_backend_get_default_object (CalBackend *backend, Cal *cal)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_default_object != NULL);
    (* CLASS (backend)->get_default_object) (backend, cal);
}

/**
 * cal_backend_get_object:
 * @backend: A calendar backend.
 * @uid: Unique identifier for a calendar object.
 * @rid: ID for the object's recurrence to get.
 *
 * Queries a calendar backend for a calendar object based on its unique
 * identifier and its recurrence ID (if a recurrent appointment).
 *
 * Return value: The string representation of a complete calendar wrapping the
 * the sought object, or NULL if no object had the specified UID.
 **/
void
cal_backend_get_object (CalBackend *backend, Cal *cal, const char *uid, const char *rid)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (uid != NULL);

    g_assert (CLASS (backend)->get_object != NULL);
    (* CLASS (backend)->get_object) (backend, cal, uid, rid);
}

/**
 * cal_backend_get_object_list:
 * @backend: 
 * @type: 
 * 
 * 
 * 
 * Return value: 
 **/
void
cal_backend_get_object_list (CalBackend *backend, Cal *cal, const char *sexp)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));

    g_assert (CLASS (backend)->get_object_list != NULL);
    return (* CLASS (backend)->get_object_list) (backend, cal, sexp);
}

/**
 * cal_backend_get_free_busy:
 * @backend: A calendar backend.
 * @users: List of users to get free/busy information for.
 * @start: Start time for query.
 * @end: End time for query.
 * 
 * Gets a free/busy object for the given time interval
 * 
 * Return value: a list of CalObj's
 **/
void
cal_backend_get_free_busy (CalBackend *backend, Cal *cal, GList *users, time_t start, time_t end)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (start != -1 && end != -1);
    g_return_if_fail (start <= end);

    g_assert (CLASS (backend)->get_free_busy != NULL);
    (* CLASS (backend)->get_free_busy) (backend, cal, users, start, end);
}

/**
 * cal_backend_get_changes:
 * @backend: A calendar backend
 * @type: Bitmask with types of objects to return.
 * @change_id: A unique uid for the callers change list
 * 
 * Builds a sequence of objects and the type of change that occurred on them since
 * the last time the give change_id was seen
 * 
 * Return value: A list of the objects that changed and the type of change
 **/
void
cal_backend_get_changes (CalBackend *backend, Cal *cal, CalObjType type, const char *change_id) 
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (change_id != NULL);

    g_assert (CLASS (backend)->get_changes != NULL);
    (* CLASS (backend)->get_changes) (backend, cal, type, change_id);
}

/**
 * cal_backend_discard_alarm
 * @backend: A calendar backend.
 * @uid: UID of the component to discard the alarm from.
 * @auid: Alarm ID.
 *
 * Discards an alarm from the given component. This allows the specific backend
 * to do whatever is needed to really discard the alarm.
 *
 **/
void
cal_backend_discard_alarm (CalBackend *backend, Cal *cal, const char *uid, const char *auid)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (uid != NULL);
    g_return_if_fail (auid != NULL);

    g_assert (CLASS (backend)->discard_alarm != NULL);
    (* CLASS (backend)->discard_alarm) (backend, cal, uid, auid);
}

void
cal_backend_create_object (CalBackend *backend, Cal *cal, const char *calobj)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (calobj != NULL);

    g_assert (CLASS (backend)->create_object != NULL);
    (* CLASS (backend)->create_object) (backend, cal, calobj);
}

void
cal_backend_modify_object (CalBackend *backend, Cal *cal, const char *calobj, CalObjModType mod)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (calobj != NULL);

    g_assert (CLASS (backend)->modify_object != NULL);
    (* CLASS (backend)->modify_object) (backend, cal, calobj, mod);
}

/**
 * cal_backend_remove_object:
 * @backend: A calendar backend.
 * @uid: Unique identifier of the object to remove.
 * @rid: A recurrence ID.
 * 
 * Removes an object in a calendar backend.  The backend will notify all of its
 * clients about the change.
 * 
 **/
void
cal_backend_remove_object (CalBackend *backend, Cal *cal, const char *uid, const char *rid, CalObjModType mod)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (uid != NULL);

    g_assert (CLASS (backend)->remove_object != NULL);
    (* CLASS (backend)->remove_object) (backend, cal, uid, rid, mod);
}

void
cal_backend_receive_objects (CalBackend *backend, Cal *cal, const char *calobj)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (calobj != NULL);

    g_assert (CLASS (backend)->receive_objects != NULL);
    return (* CLASS (backend)->receive_objects) (backend, cal, calobj);
}

void
cal_backend_send_objects (CalBackend *backend, Cal *cal, const char *calobj)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (calobj != NULL);

    g_assert (CLASS (backend)->send_objects != NULL);
    return (* CLASS (backend)->send_objects) (backend, cal, calobj);
}

/**
 * cal_backend_get_timezone:
 * @backend: A calendar backend.
 * @tzid: Unique identifier of a VTIMEZONE object. Note that this must not be
 * NULL.
 * 
 * Returns the icaltimezone* corresponding to the TZID, or NULL if the TZID
 * can't be found.
 * 
 * Returns: The icaltimezone* corresponding to the given TZID, or NULL.
 **/
void
cal_backend_get_timezone (CalBackend *backend, Cal *cal, const char *tzid)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (tzid != NULL);

    g_assert (CLASS (backend)->get_timezone != NULL);
    (* CLASS (backend)->get_timezone) (backend, cal, tzid);
}

/**
 * cal_backend_set_default_timezone:
 * @backend: A calendar backend.
 * @tzid: The TZID identifying the timezone.
 * 
 * Sets the default timezone for the calendar, which is used to resolve
 * DATE and floating DATE-TIME values.
 * 
 * Returns: TRUE if the VTIMEZONE data for the timezone was found, or FALSE if
 * not.
 **/
void
cal_backend_set_default_timezone (CalBackend *backend, Cal *cal, const char *tzid)
{
    g_return_if_fail (backend != NULL);
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (tzid != NULL);

    g_assert (CLASS (backend)->set_default_timezone != NULL);
    (* CLASS (backend)->set_default_timezone) (backend, cal, tzid);
}

/**
 * cal_backend_add_timezone
 * @backend: A calendar backend.
 * @tzobj: The timezone object, in a string.
 *
 * Add a timezone object to the given backend.
 *
 * Returns: TRUE if successful, or FALSE if not.
 */
void
cal_backend_add_timezone (CalBackend *backend, Cal *cal, const char *tzobj)
{
    g_return_if_fail (IS_CAL_BACKEND (backend));
    g_return_if_fail (tzobj != NULL);
    g_return_if_fail (CLASS (backend)->add_timezone != NULL);

    (* CLASS (backend)->add_timezone) (backend, cal, tzobj);
}

icaltimezone *
cal_backend_internal_get_default_timezone (CalBackend *backend)
{
    g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
    g_return_val_if_fail (CLASS (backend)->internal_get_default_timezone != NULL, NULL);

    return (* CLASS (backend)->internal_get_default_timezone) (backend);
}

icaltimezone *
cal_backend_internal_get_timezone (CalBackend *backend, const char *tzid)
{
    g_return_val_if_fail (IS_CAL_BACKEND (backend), NULL);
    g_return_val_if_fail (tzid != NULL, NULL);
    g_return_val_if_fail (CLASS (backend)->internal_get_timezone != NULL, NULL);

    return (* CLASS (backend)->internal_get_timezone) (backend, tzid);
}

/**
 * cal_backend_notify_mode:
 * @backend: A calendar backend.
 * @status: Status of the mode set
 * @mode: the current mode
 *
 * Notifies each of the backend's listeners about the results of a
 * setMode call.
 **/
void
cal_backend_notify_mode (CalBackend *backend,
             GNOME_Evolution_Calendar_Listener_SetModeStatus status, 
             GNOME_Evolution_Calendar_CalMode mode)
{
    CalBackendPrivate *priv = backend->priv;
    GList *l;

    for (l = priv->clients; l; l = l->next)
        cal_notify_mode (l->data, status, mode);
}

/**
 * cal_backend_notify_error:
 * @backend: A calendar backend.
 * @message: Error message
 *
 * Notifies each of the backend's listeners about an error
 **/
void
cal_backend_notify_error (CalBackend *backend, const char *message)
{
    CalBackendPrivate *priv = backend->priv;
    GList *l;

    for (l = priv->clients; l; l = l->next)
        cal_notify_error (l->data, message);
}

static void
add_category_cb (gpointer name, gpointer category, gpointer data)
{
    GNOME_Evolution_Calendar_StringSeq *seq = data;

    seq->_buffer[seq->_length++] = CORBA_string_dup (name);
}

static void
notify_categories_changed (CalBackend *backend)
{
    CalBackendPrivate *priv = backend->priv;
    GNOME_Evolution_Calendar_StringSeq *seq;
    GList *l;

    /* Build the sequence of category names */
    seq = GNOME_Evolution_Calendar_StringSeq__alloc ();
    seq->_length = 0;
    seq->_maximum = g_hash_table_size (priv->categories);
    seq->_buffer = CORBA_sequence_CORBA_string_allocbuf (seq->_maximum);
    CORBA_sequence_set_release (seq, TRUE);

    g_hash_table_foreach (priv->categories, add_category_cb, seq);

    /* Notify the clients */
    for (l = priv->clients; l; l = l->next)
        cal_notify_categories_changed (l->data, seq);

    CORBA_free (seq);
}

static gboolean
idle_notify_categories_changed (gpointer data)
{
    CalBackend *backend = CAL_BACKEND (data);
    CalBackendPrivate *priv = backend->priv;

    if (g_hash_table_size (priv->changed_categories)) {
        notify_categories_changed (backend);
        g_hash_table_foreach_remove (priv->changed_categories, prune_changed_categories, NULL);
    }

    priv->category_idle_id = 0;
    
    return FALSE;
}

/**
 * cal_backend_ref_categories:
 * @backend: A calendar backend
 * @categories: a list of categories
 *
 * Adds 1 to the refcount of each of the named categories. If any of
 * the categories are new, clients will be notified of the updated
 * category list at idle time.
 **/
void
cal_backend_ref_categories (CalBackend *backend, GSList *categories)
{
    CalBackendPrivate *priv;
    CalBackendCategory *c;
    const char *name;

    priv = backend->priv;

    while (categories) {
        name = categories->data;
        c = g_hash_table_lookup (priv->categories, name);

        if (c)
            c->refcount++;
        else {
            /* See if it was recently removed */

            c = g_hash_table_lookup (priv->changed_categories, name);
            if (c && c->refcount == 0) {
                /* Move it back to the set of live categories */
                g_hash_table_remove (priv->changed_categories, c->name);

                c->refcount = 1;
                g_hash_table_insert (priv->categories, c->name, c);
            } else {
                /* Create a new category */
                c = g_new (CalBackendCategory, 1);
                c->name = g_strdup (name);
                c->refcount = 1;
                g_hash_table_insert (priv->categories, c->name, c);
                g_hash_table_insert (priv->changed_categories, c->name, c);
            }
        }

        categories = categories->next;
    }

    if (g_hash_table_size (priv->changed_categories) &&
        !priv->category_idle_id)
        priv->category_idle_id = g_idle_add (idle_notify_categories_changed, backend);
}

/**
 * cal_backend_unref_categories:
 * @backend: A calendar backend
 * @categories: a list of categories
 *
 * Subtracts 1 from the refcount of each of the named categories. If
 * any of the refcounts go down to 0, clients will be notified of the
 * updated category list at idle time.
 **/
void
cal_backend_unref_categories (CalBackend *backend, GSList *categories)
{
    CalBackendPrivate *priv;
    CalBackendCategory *c;
    const char *name;

    priv = backend->priv;

    while (categories) {
        name = categories->data;
        c = g_hash_table_lookup (priv->categories, name);

        if (c) {
            g_assert (c != NULL);
            g_assert (c->refcount > 0);

            c->refcount--;

            if (c->refcount == 0) {
                g_hash_table_remove (priv->categories, c->name);
                g_hash_table_insert (priv->changed_categories, c->name, c);
            }
        }

        categories = categories->next;
    }

    if (g_hash_table_size (priv->changed_categories) &&
        !priv->category_idle_id)
        priv->category_idle_id = g_idle_add (idle_notify_categories_changed, backend);
}