/*
 *  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; version 2 of the License ONLY.
 *
 *  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 Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <gio/gio.h>

#include "xfconf-lifecycle-manager.h"


#define SHUTDOWN_TIMEOUT_SECONDS 300


enum
{
    SIGNAL_SHUTDOWN,
    N_SIGNALS,
};


static void xfconf_lifecycle_manager_finalize(GObject *object);


struct _XfconfLifecycleManagerPrivate
{
    GMutex lock;

    guint timeout_id;
    guint use_count;
    gboolean shutdown_emitted;
};


static guint lifecycle_manager_signals[N_SIGNALS];


G_DEFINE_TYPE_WITH_PRIVATE(XfconfLifecycleManager, xfconf_lifecycle_manager, G_TYPE_OBJECT)


static void
xfconf_lifecycle_manager_class_init(XfconfLifecycleManagerClass *klass)
{
    GObjectClass *gobject_class = G_OBJECT_CLASS(klass);

    gobject_class->finalize = xfconf_lifecycle_manager_finalize;

    lifecycle_manager_signals[SIGNAL_SHUTDOWN] =
        g_signal_new("shutdown", XFCONF_TYPE_LIFECYCLE_MANAGER, G_SIGNAL_RUN_LAST, 0,
                     NULL, NULL, g_cclosure_marshal_VOID__VOID, G_TYPE_NONE, 0);
}


static void
xfconf_lifecycle_manager_init(XfconfLifecycleManager *manager)
{
    manager->priv = xfconf_lifecycle_manager_get_instance_private(manager);
    g_mutex_init(&manager->priv->lock);
    manager->priv->timeout_id = 0;
    manager->priv->use_count = 0;
    manager->priv->shutdown_emitted = FALSE;
}


static void
xfconf_lifecycle_manager_finalize(GObject *object)
{
    XfconfLifecycleManager *manager = XFCONF_LIFECYCLE_MANAGER(object);

    g_mutex_clear(&manager->priv->lock);

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


static gboolean
xfconf_lifecycle_manager_timeout(gpointer user_data)
{
    XfconfLifecycleManager *manager = user_data;

    g_mutex_lock(&manager->priv->lock);

    /* reschedule the timeout if the daemon is currently in use */
    if (manager->priv->use_count > 0) {
        g_mutex_unlock(&manager->priv->lock);
        return TRUE;
    }

    /* reset the timeout id */
    manager->priv->timeout_id = 0;

    /* emit the shutdown signal */
    g_signal_emit(manager, lifecycle_manager_signals[SIGNAL_SHUTDOWN], 0);

    /* set the shutdown emitted flag to force other threads not to reschedule
     * the timeout */
    manager->priv->shutdown_emitted = TRUE;

    g_mutex_unlock(&manager->priv->lock);

    return FALSE;
}


XfconfLifecycleManager *
xfconf_lifecycle_manager_new(void)
{
    return g_object_new(XFCONF_TYPE_LIFECYCLE_MANAGER, NULL);
}


void
xfconf_lifecycle_manager_start(XfconfLifecycleManager *manager)
{
    g_return_if_fail(XFCONF_IS_LIFECYCLE_MANAGER(manager));

    g_mutex_lock(&manager->priv->lock);

    /* ignore if there already is a timeout scheduled */
    if (manager->priv->timeout_id != 0) {
        g_mutex_unlock(&manager->priv->lock);
        return;
    }

    manager->priv->timeout_id =
        g_timeout_add_seconds(SHUTDOWN_TIMEOUT_SECONDS,
                              xfconf_lifecycle_manager_timeout,
                              manager);

    g_mutex_unlock(&manager->priv->lock);
}


gboolean
xfconf_lifecycle_manager_keep_alive(XfconfLifecycleManager *manager)
{
    g_return_val_if_fail(XFCONF_IS_LIFECYCLE_MANAGER(manager), G_DBUS_METHOD_INVOCATION_UNHANDLED);

    g_mutex_lock(&manager->priv->lock);

    /* if the shutdown signal has been emitted, there's nothing we can do to prevent
     * a shutdown anymore */
    if (manager->priv->shutdown_emitted) {
        g_mutex_unlock(&manager->priv->lock);
        return G_DBUS_METHOD_INVOCATION_UNHANDLED;
    }

    /* drop existing timeout, if any */
    if (manager->priv->timeout_id != 0) {
        g_source_remove(manager->priv->timeout_id);
    }

    /* reschedule the shutdown timeout */
    manager->priv->timeout_id =
        g_timeout_add_seconds(SHUTDOWN_TIMEOUT_SECONDS,
                              xfconf_lifecycle_manager_timeout,
                              manager);

    g_mutex_unlock(&manager->priv->lock);

    return G_DBUS_METHOD_INVOCATION_UNHANDLED;
}


gboolean
xfconf_lifecycle_manager_increment_use_count(XfconfLifecycleManager *manager)
{
    g_return_val_if_fail(XFCONF_IS_LIFECYCLE_MANAGER(manager), G_DBUS_METHOD_INVOCATION_UNHANDLED);

    g_mutex_lock(&manager->priv->lock);

    manager->priv->use_count++;

    g_mutex_unlock(&manager->priv->lock);

    return G_DBUS_METHOD_INVOCATION_UNHANDLED;
}


gboolean
xfconf_lifecycle_manager_decrement_use_count(XfconfLifecycleManager *manager)
{
    g_return_val_if_fail(XFCONF_IS_LIFECYCLE_MANAGER(manager), G_DBUS_METHOD_INVOCATION_HANDLED);

    g_mutex_lock(&manager->priv->lock);

    /* decrement the use count, make sure not to drop below zero */
    if (manager->priv->use_count > 0) {
        manager->priv->use_count--;
    }

    g_mutex_unlock(&manager->priv->lock);

    return G_DBUS_METHOD_INVOCATION_HANDLED;
}
