/* 
 * Copyright (C) 2004 Andrew Beekhof <andrew@beekhof.net>
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <crm_internal.h>

#ifndef _GNU_SOURCE
#  define _GNU_SOURCE
#endif

#include <stdlib.h>
#include <signal.h>
#include <errno.h>

#include <crm/crm.h>
#include <crm/common/mainloop.h>

static gboolean
crm_trigger_prepare(GSource * source, gint * timeout)
{
    crm_trigger_t *trig = (crm_trigger_t *) source;

    /* cluster-glue's FD and IPC related sources make use of
     * g_source_add_poll() but do not set a timeout in their prepare
     * functions
     *
     * This means mainloop's poll() will block until an event for one
     * of these sources occurs - any /other/ type of source, such as
     * this one or g_idle_*, that doesn't use g_source_add_poll() is
     * S-O-L and wont be processed until there is something fd-based
     * happens.
     *
     * Luckily the timeout we can set here affects all sources and
     * puts an upper limit on how long poll() can take.
     *
     * So unconditionally set a small-ish timeout, not too small that
     * we're in constant motion, which will act as an upper bound on
     * how long the signal handling might be delayed for.
     */
    *timeout = 500;             /* Timeout in ms */

    return trig->trigger;
}

static gboolean
crm_trigger_check(GSource * source)
{
    crm_trigger_t *trig = (crm_trigger_t *) source;

    return trig->trigger;
}

static gboolean
crm_trigger_dispatch(GSource * source, GSourceFunc callback, gpointer userdata)
{
    crm_trigger_t *trig = (crm_trigger_t *) source;

    trig->trigger = FALSE;

    if (callback) {
        return callback(trig->user_data);
    }
    return TRUE;
}

static GSourceFuncs crm_trigger_funcs = {
    crm_trigger_prepare,
    crm_trigger_check,
    crm_trigger_dispatch,
    NULL
};

static crm_trigger_t *
mainloop_setup_trigger(GSource * source, int priority, gboolean(*dispatch) (gpointer user_data),
                       gpointer userdata)
{
    crm_trigger_t *trigger = NULL;

    trigger = (crm_trigger_t *) source;

    trigger->id = 0;
    trigger->trigger = FALSE;
    trigger->user_data = userdata;

    if (dispatch) {
        g_source_set_callback(source, dispatch, trigger, NULL);
    }

    g_source_set_priority(source, priority);
    g_source_set_can_recurse(source, FALSE);

    trigger->id = g_source_attach(source, NULL);
    return trigger;
}

crm_trigger_t *
mainloop_add_trigger(int priority, gboolean(*dispatch) (gpointer user_data), gpointer userdata)
{
    GSource *source = NULL;

    CRM_ASSERT(sizeof(crm_trigger_t) > sizeof(GSource));
    source = g_source_new(&crm_trigger_funcs, sizeof(crm_trigger_t));
    CRM_ASSERT(source != NULL);

    return mainloop_setup_trigger(source, priority, dispatch, userdata);
}

void
mainloop_set_trigger(crm_trigger_t * source)
{
    source->trigger = TRUE;
}

gboolean
mainloop_destroy_trigger(crm_trigger_t * source)
{
    source->trigger = FALSE;
    if (source->id > 0) {
        g_source_remove(source->id);
    }
    return TRUE;
}

typedef struct signal_s {
    crm_trigger_t trigger;      /* must be first */
    void (*handler) (int sig);
    int signal;

} crm_signal_t;

static crm_signal_t *crm_signals[NSIG];

static gboolean
crm_signal_dispatch(GSource * source, GSourceFunc callback, gpointer userdata)
{
    crm_signal_t *sig = (crm_signal_t *) source;

    crm_info("Invoking handler for signal %d: %s", sig->signal, strsignal(sig->signal));

    sig->trigger.trigger = FALSE;
    if (sig->handler) {
        sig->handler(sig->signal);
    }
    return TRUE;
}

static void
mainloop_signal_handler(int sig)
{
    if (sig > 0 && sig < NSIG && crm_signals[sig] != NULL) {
        mainloop_set_trigger((crm_trigger_t *) crm_signals[sig]);
    }
}

static GSourceFuncs crm_signal_funcs = {
    crm_trigger_prepare,
    crm_trigger_check,
    crm_signal_dispatch,
    NULL
};

gboolean
crm_signal(int sig, void (*dispatch) (int sig))
{
    sigset_t mask;
    struct sigaction sa;
    struct sigaction old;

    if (sigemptyset(&mask) < 0) {
        crm_perror(LOG_ERR, "Call to sigemptyset failed");
        return FALSE;
    }

    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_handler = dispatch;
    sa.sa_flags = SA_RESTART;
    sa.sa_mask = mask;

    if (sigaction(sig, &sa, &old) < 0) {
        crm_perror(LOG_ERR, "Could not install signal handler for signal %d", sig);
        return FALSE;
    }

    return TRUE;
}

gboolean
mainloop_add_signal(int sig, void (*dispatch) (int sig))
{
    GSource *source = NULL;
    int priority = G_PRIORITY_HIGH - 1;

    if (sig == SIGTERM) {
        /* TERM is higher priority than other signals,
         *   signals are higher priority than other ipc.
         * Yes, minus: smaller is "higher"
         */
        priority--;
    }

    if (sig >= NSIG || sig < 0) {
        crm_err("Signal %d is out of range", sig);
        return FALSE;

    } else if (crm_signals[sig] != NULL) {
        crm_err("Signal handler for %d is already installed", sig);
        return FALSE;
    }

    CRM_ASSERT(sizeof(crm_signal_t) > sizeof(GSource));
    source = g_source_new(&crm_signal_funcs, sizeof(crm_signal_t));

    crm_signals[sig] = (crm_signal_t *) mainloop_setup_trigger(source, priority, NULL, NULL);
    CRM_ASSERT(crm_signals[sig] != NULL);

    crm_signals[sig]->handler = dispatch;
    crm_signals[sig]->signal = sig;

    if (crm_signal(sig, mainloop_signal_handler) == FALSE) {
        crm_signal_t *tmp = crm_signals[sig];

        crm_signals[sig] = NULL;

        mainloop_destroy_trigger((crm_trigger_t *) tmp);
        return FALSE;
    }
#if 0
    /* If we want signals to interrupt mainloop's poll(), instead of waiting for
     * the timeout, then we should call siginterrupt() below
     *
     * For now, just enforce a low timeout
     */
    if (siginterrupt(sig, 1) < 0) {
        crm_perror(LOG_INFO, "Could not enable system call interruptions for signal %d", sig);
    }
#endif

    return TRUE;
}

gboolean
mainloop_destroy_signal(int sig)
{
    crm_signal_t *tmp = NULL;

    if (sig >= NSIG || sig < 0) {
        crm_err("Signal %d is out of range", sig);
        return FALSE;

    } else if (crm_signal(sig, NULL) == FALSE) {
        crm_perror(LOG_ERR, "Could not uninstall signal handler for signal %d", sig);
        return FALSE;

    } else if (crm_signals[sig] == NULL) {
        return TRUE;
    }

    tmp = crm_signals[sig];
    crm_signals[sig] = NULL;
    mainloop_destroy_trigger((crm_trigger_t *) tmp);
    return TRUE;
}