/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */

/*

 * Copyright © 2012 – 2017 Red Hat, Inc.

 *

 * 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 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, see <http://www.gnu.org/licenses/>.

 */

#include "config.h"

#include "goaalarm.h"

#ifdef HAVE_TIMERFD

#include <sys/timerfd.h>

#endif

#include <errno.h>

#include <unistd.h>

#include <string.h>

#include <glib.h>

#include <gio/gio.h>

#include <gio/gunixinputstream.h>

#define MAX_TIMEOUT_INTERVAL (10 *1000)

typedef enum

{

  GOA_ALARM_TYPE_UNSCHEDULED,

  GOA_ALARM_TYPE_TIMER,

  GOA_ALARM_TYPE_TIMEOUT,

} GoaAlarmType;

struct _GoaAlarmPrivate

{

  GDateTime *time;

  GDateTime *previous_wakeup_time;

  GMainContext *context;

  GSource *immediate_wakeup_source;

  GRecMutex lock;

  GoaAlarmType type;

  GSource *scheduled_wakeup_source;

  GInputStream *stream; /* NULL, unless using timerfd */

};

enum

{

  FIRED,

  REARMED,

  NUMBER_OF_SIGNALS,

};

enum

{

  PROP_0,

  PROP_TIME

};

static void schedule_wakeups (GoaAlarm *self);

static void schedule_wakeups_with_timeout_source (GoaAlarm *self);

static void goa_alarm_set_time (GoaAlarm *self, GDateTime *time);

static void clear_wakeup_source_pointer (GoaAlarm *self);

static guint signals[NUMBER_OF_SIGNALS] = { 0 };

G_DEFINE_TYPE (GoaAlarm, goa_alarm, G_TYPE_OBJECT);

static void

goa_alarm_dispose (GObject *object)

{

  GoaAlarm *self = GOA_ALARM (object);

  g_clear_object (&self->priv->stream);

  g_clear_pointer (&self->priv->immediate_wakeup_source, (GDestroyNotify) g_source_destroy);

  g_clear_pointer (&self->priv->scheduled_wakeup_source, (GDestroyNotify) g_source_destroy);

  g_clear_pointer (&self->priv->context, (GDestroyNotify) g_main_context_unref);

  g_clear_pointer (&self->priv->time, (GDestroyNotify) g_date_time_unref);

  g_clear_pointer (&self->priv->previous_wakeup_time, (GDestroyNotify) g_date_time_unref);

  G_OBJECT_CLASS (goa_alarm_parent_class)->dispose (object);

}

static void

goa_alarm_finalize (GObject *object)

{

  GoaAlarm *self = GOA_ALARM (object);

  g_rec_mutex_clear (&self->priv->lock);

  G_OBJECT_CLASS (goa_alarm_parent_class)->finalize (object);

}

static void

goa_alarm_set_property (GObject      *object,

                        guint         property_id,

                        const GValue *value,

                        GParamSpec   *param_spec)

{

  GoaAlarm *self = GOA_ALARM (object);

  GDateTime *time;

  switch (property_id)

    {

    case PROP_TIME:

      time = (GDateTime *) g_value_get_boxed (value);

      goa_alarm_set_time (self, time);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, param_spec);

      break;

    }

}

static void

goa_alarm_get_property (GObject    *object,

                        guint       property_id,

                        GValue     *value,

                        GParamSpec *param_spec)

{

  GoaAlarm *self = GOA_ALARM (object);

  switch (property_id)

    {

    case PROP_TIME:

      g_value_set_boxed (value, self->priv->time);

      break;

    default:

      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, param_spec);

      break;

    }

}

static void

goa_alarm_class_init (GoaAlarmClass *klass)

{

  GObjectClass *object_class;

  object_class = G_OBJECT_CLASS (klass);

  object_class->dispose = goa_alarm_dispose;

  object_class->finalize = goa_alarm_finalize;

  object_class->get_property = goa_alarm_get_property;

  object_class->set_property = goa_alarm_set_property;

  g_type_class_add_private (klass, sizeof (GoaAlarmPrivate));

  signals[FIRED] = g_signal_new ("fired",

                                 G_TYPE_FROM_CLASS (klass),

                                 G_SIGNAL_RUN_LAST,

                                 0, NULL, NULL, NULL, G_TYPE_NONE, 0);

  signals[REARMED] = g_signal_new ("rearmed",

                                   G_TYPE_FROM_CLASS (klass),

                                   G_SIGNAL_RUN_LAST,

                                   0, NULL, NULL, NULL, G_TYPE_NONE, 0);

  g_object_class_install_property (object_class,

                                   PROP_TIME,

                                   g_param_spec_boxed ("time",

                                                       "Time",

                                                       "Time to fire",

                                                       G_TYPE_DATE_TIME,

                                                       G_PARAM_READWRITE));

}

static void

goa_alarm_init (GoaAlarm *self)

{

  self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self, GOA_TYPE_ALARM, GoaAlarmPrivate);

  g_rec_mutex_init (&self->priv->lock);

}

static void

fire_alarm (GoaAlarm *self)

{

  g_signal_emit (G_OBJECT (self), signals[FIRED], 0);

}

static void

rearm_alarm (GoaAlarm *self)

{

  g_signal_emit (G_OBJECT (self), signals[REARMED], 0);

}

static void

fire_or_rearm_alarm (GoaAlarm *self)

{

  GTimeSpan time_until_fire;

  GTimeSpan previous_time_until_fire;

  GDateTime *now;

  now = g_date_time_new_now_local ();

  time_until_fire = g_date_time_difference (self->priv->time, now);

  if (self->priv->previous_wakeup_time == NULL)

    {

      self->priv->previous_wakeup_time = now;

      /* If, according to the time, we're past when we should have fired,

       * then fire the alarm.

       */

      if (time_until_fire <= 0)

        fire_alarm (self);

    }

  else

    {

      previous_time_until_fire =

          g_date_time_difference (self->priv->time,

                                  self->priv->previous_wakeup_time);

      g_date_time_unref (self->priv->previous_wakeup_time);

      self->priv->previous_wakeup_time = now;

      /* If, according to the time, we're past when we should have fired,

       * and this is the first wakeup where that's been true then fire

       * the alarm. The first check makes sure we don't fire prematurely,

       * and the second check makes sure we don't fire more than once

       */

      if (time_until_fire <= 0 && previous_time_until_fire > 0)

        {

          fire_alarm (self);

          /* If, according to the time, we're before when we should fire,

           * and we previously fired the alarm, then we've jumped back in

           * time and need to rearm the alarm.

           */

        }

      else if (time_until_fire > 0 && previous_time_until_fire <= 0)

        {

          rearm_alarm (self);

        }

    }

}

static gboolean

on_immediate_wakeup_source_ready (GoaAlarm *self)

{

  g_return_val_if_fail (self->priv->type != GOA_ALARM_TYPE_UNSCHEDULED, FALSE);

  g_rec_mutex_lock (&self->priv->lock);

  fire_or_rearm_alarm (self);

  g_rec_mutex_unlock (&self->priv->lock);

  return FALSE;

}

#ifdef HAVE_TIMERFD

static gboolean

on_timer_source_ready (GObject *stream, GoaAlarm *self)

{

  gint64 number_of_fires;

  gssize bytes_read;

  gboolean run_again = FALSE;

  GError *error = NULL;

  g_return_val_if_fail (GOA_IS_ALARM (self), FALSE);

  g_rec_mutex_lock (&self->priv->lock);

  if (self->priv->type != GOA_ALARM_TYPE_TIMER)

    {

      g_warning ("GoaAlarm: timer source ready callback called "

                 "when timer source isn't supposed to be used. "

                 "Current timer type is %u", self->priv->type);

      goto out;

    }

  bytes_read =

    g_pollable_input_stream_read_nonblocking (G_POLLABLE_INPUT_STREAM (stream),

                                              &number_of_fires, sizeof (gint64),

                                              NULL, &error);

  if (bytes_read < 0)

    {

      if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))

        g_debug ("GoaAlarm: discontinuity detected from timer fd");

      else

        {

          g_warning ("GoaAlarm: failed to read from timer fd: %s\n",

                     error->message);

          goto out;

        }

    }

  if (bytes_read == sizeof (gint64))

    {

      if (number_of_fires < 0 || number_of_fires > 1)

        {

          g_warning ("GoaAlarm: expected timerfd to report firing once,"

                     "but it reported firing %ld times\n", (long) number_of_fires);

        }

    }

  fire_or_rearm_alarm (self);

  run_again = TRUE;

out:

  g_rec_mutex_unlock (&self->priv->lock);

  g_clear_error (&error);

  return run_again;

}

#endif

static gboolean

schedule_wakeups_with_timerfd (GoaAlarm *self)

{

#ifdef HAVE_TIMERFD

  struct itimerspec timer_spec;

  int fd;

  int result;

  GSource *source;

  static gboolean seen_before = FALSE;

  if (!seen_before)

    {

      g_debug ("GoaAlarm: trying to use kernel timer");

      seen_before = TRUE;

    }

  fd = timerfd_create (CLOCK_REALTIME, TFD_CLOEXEC | TFD_NONBLOCK);

  if (fd < 0)

    {

      g_debug ("GoaAlarm: could not create timer fd: %s", strerror (errno));

      return FALSE;

    }

  memset (&timer_spec, 0, sizeof (timer_spec));

  timer_spec.it_value.tv_sec = g_date_time_to_unix (self->priv->time) + 1;

  result = timerfd_settime (fd,

                            TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET,

                            &timer_spec, NULL);

  if (result < 0)

    {

      g_debug ("GoaAlarm: could not set timer: %s", strerror (errno));

      return FALSE;

    }

  self->priv->type = GOA_ALARM_TYPE_TIMER;

  self->priv->stream = g_unix_input_stream_new (fd, TRUE);

  source =

    g_pollable_input_stream_create_source (G_POLLABLE_INPUT_STREAM

                                           (self->priv->stream),

                                           NULL);

  self->priv->scheduled_wakeup_source = source;

  g_source_set_callback (self->priv->scheduled_wakeup_source,

                         (GSourceFunc) on_timer_source_ready, self,

                         (GDestroyNotify) clear_wakeup_source_pointer);

  g_source_attach (self->priv->scheduled_wakeup_source, self->priv->context);

  g_source_unref (source);

  return TRUE;

#endif /*HAVE_TIMERFD */

  return FALSE;

}

static gboolean

on_timeout_source_ready (GoaAlarm *self)

{

  g_return_val_if_fail (GOA_IS_ALARM (self), FALSE);

  g_rec_mutex_lock (&self->priv->lock);

  if (self->priv->type == GOA_ALARM_TYPE_UNSCHEDULED)

    goto out;

  fire_or_rearm_alarm (self);

  schedule_wakeups_with_timeout_source (self);

out:

  g_rec_mutex_unlock (&self->priv->lock);

  return FALSE;

}

static void

clear_wakeup_source_pointer (GoaAlarm *self)

{

  self->priv->scheduled_wakeup_source = NULL;

}

static void

schedule_wakeups_with_timeout_source (GoaAlarm *self)

{

  GDateTime *now;

  GSource   *source;

  GTimeSpan  time_span;

  guint      interval;

  self->priv->type = GOA_ALARM_TYPE_TIMEOUT;

  now = g_date_time_new_now_local ();

  time_span = g_date_time_difference (self->priv->time, now);

  g_date_time_unref (now);

  time_span =

    CLAMP (time_span, 1000 *G_TIME_SPAN_MILLISECOND,

           G_MAXUINT *G_TIME_SPAN_MILLISECOND);

  interval = (guint) time_span / G_TIME_SPAN_MILLISECOND;

  /* We poll every 10 seconds or so because we want to catch time skew

   */

  interval = MIN (interval, MAX_TIMEOUT_INTERVAL);

  source = g_timeout_source_new (interval);

  self->priv->scheduled_wakeup_source = source;

  g_source_set_callback (self->priv->scheduled_wakeup_source,

                         (GSourceFunc)

                         on_timeout_source_ready,

                         self, (GDestroyNotify) clear_wakeup_source_pointer);

  g_source_attach (self->priv->scheduled_wakeup_source, self->priv->context);

  g_source_unref (source);

}

static void

schedule_wakeups (GoaAlarm *self)

{

  gboolean wakeup_scheduled;

  wakeup_scheduled = schedule_wakeups_with_timerfd (self);

  if (!wakeup_scheduled)

    {

      static gboolean seen_before = FALSE;

      if (!seen_before)

        {

          g_debug ("GoaAlarm: falling back to polling timeout");

          seen_before = TRUE;

        }

      schedule_wakeups_with_timeout_source (self);

    }

}

static void

clear_immediate_wakeup_source_pointer (GoaAlarm *self)

{

  self->priv->immediate_wakeup_source = NULL;

}

static void

schedule_immediate_wakeup (GoaAlarm *self)

{

  GSource *source;

  source = g_idle_source_new ();

  self->priv->immediate_wakeup_source = source;

  g_source_set_callback (self->priv->immediate_wakeup_source,

                         (GSourceFunc)

                         on_immediate_wakeup_source_ready,

                         self,

                         (GDestroyNotify) clear_immediate_wakeup_source_pointer);

  g_source_attach (self->priv->immediate_wakeup_source, self->priv->context);

  g_source_unref (source);

}

static void

goa_alarm_set_time (GoaAlarm *self, GDateTime *time)

{

  g_rec_mutex_lock (&self->priv->lock);

  g_date_time_ref (time);

  self->priv->time = time;

  if (self->priv->context == NULL)

    self->priv->context = g_main_context_ref (g_main_context_default ());

  schedule_wakeups (self);

  /* Wake up right away, in case it's already expired leaving the gate */

  schedule_immediate_wakeup (self);

  g_rec_mutex_unlock (&self->priv->lock);

  g_object_notify (G_OBJECT (self), "time");

}

GDateTime *

goa_alarm_get_time (GoaAlarm *self)

{

  return self->priv->time;

}

GoaAlarm *

goa_alarm_new (GDateTime *alarm_time)

{

  GoaAlarm *self;

  self = GOA_ALARM (g_object_new (GOA_TYPE_ALARM, "time", alarm_time, NULL));

  return GOA_ALARM (self);

}