/*
 * Copyright (c) 2002-2013, 2015 Balabit
 * Copyright (c) 1998-2013, 2015 Balázs Scheidler
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, or (at your option) any later version.
 *
 * 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 St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * As an additional exemption you are allowed to compile & link against the
 * OpenSSL libraries as published by the OpenSSL project. See the file
 * COPYING for details.
 *
 */
#include "correlation.h"
#include "correlation-key.h"
#include "correlation-context.h"
#include "timeutils/cache.h"
#include "timeutils/misc.h"

void
correlation_state_tx_begin(CorrelationState *self)
{
  g_mutex_lock(&self->lock);
}

void
correlation_state_tx_end(CorrelationState *self)
{
  g_mutex_unlock(&self->lock);
}

CorrelationContext *
correlation_state_tx_lookup_context(CorrelationState *self, const CorrelationKey *key)
{
  return g_hash_table_lookup(self->state, key);
}

void
correlation_state_tx_store_context(CorrelationState *self, CorrelationContext *context, gint timeout)
{
  g_assert(context->timer == NULL);

  g_hash_table_insert(self->state, &context->key, context);
  context->timer = timer_wheel_add_timer(self->timer_wheel, timeout, self->expire_callback,
                                         correlation_context_ref(context), (GDestroyNotify) correlation_context_unref);
}

void
correlation_state_tx_remove_context(CorrelationState *self, CorrelationContext *context)
{
  /* NOTE: in expire callbacks our timer is already deleted and thus it is
   * set to NULL in which case we don't need to remove it again.  */

  if (context->timer)
    timer_wheel_del_timer(self->timer_wheel, context->timer);
  g_hash_table_remove(self->state, &context->key);
}

void
correlation_state_tx_update_context(CorrelationState *self, CorrelationContext *context, gint timeout)
{
  g_assert(context->timer != NULL);

  timer_wheel_mod_timer(self->timer_wheel, context->timer, timeout);
}

void
correlation_state_expire_all(CorrelationState *self, gpointer caller_context)
{
  g_mutex_lock(&self->lock);
  timer_wheel_expire_all(self->timer_wheel, caller_context);
  g_mutex_unlock(&self->lock);
}

void
correlation_state_advance_time(CorrelationState *self, gint timeout, gpointer caller_context)
{
  guint64  new_time;

  g_mutex_lock(&self->lock);
  new_time = timer_wheel_get_time(self->timer_wheel) + timeout;
  timer_wheel_set_time(self->timer_wheel, new_time, caller_context);
  g_mutex_unlock(&self->lock);
}

void
correlation_state_set_time(CorrelationState *self, guint64 sec, gpointer caller_context)
{
  struct timespec now;

  /* clamp the current time between the timestamp of the current message
   * (low limit) and the current system time (high limit).  This ensures
   * that incorrect clocks do not skew the current time know by the
   * correlation engine too much. */

  get_cached_realtime(&now);
  self->last_tick = now;

  if (sec < now.tv_sec)
    now.tv_sec = sec;

  g_mutex_lock(&self->lock);
  timer_wheel_set_time(self->timer_wheel, now.tv_sec, caller_context);
  g_mutex_unlock(&self->lock);
}

guint64
correlation_state_get_time(CorrelationState *self)
{
  return timer_wheel_get_time(self->timer_wheel);
}

gboolean
correlation_state_timer_tick(CorrelationState *self, gpointer caller_context)
{
  struct timespec now;
  glong diff;
  gboolean updated = FALSE;

  g_mutex_lock(&self->lock);
  get_cached_realtime(&now);
  diff = timespec_diff_usec(&now, &self->last_tick);

  if (diff > 1e6)
    {
      glong diff_sec = (glong)(diff / 1e6);

      timer_wheel_set_time(self->timer_wheel, timer_wheel_get_time(self->timer_wheel) + diff_sec, caller_context);
      /* update last_tick, take the fraction of the seconds not calculated into this update into account */

      self->last_tick = now;
      timespec_add_usec(&self->last_tick, - (glong)(diff - diff_sec * 1e6));
      updated = TRUE;
    }
  else if (diff < 0)
    {
      /* time moving backwards, this can only happen if the computer's time
       * is changed.  We don't update patterndb's idea of the time now, wait
       * another tick instead to update that instead.
       */
      self->last_tick = now;
    }
  g_mutex_unlock(&self->lock);
  return updated;
}


CorrelationState *
correlation_state_new(TWCallbackFunc expire_callback)
{
  CorrelationState *self = g_new0(CorrelationState, 1);

  g_mutex_init(&self->lock);
  self->state = g_hash_table_new_full(correlation_key_hash, correlation_key_equal, NULL,
                                      (GDestroyNotify) correlation_context_unref);
  self->timer_wheel = timer_wheel_new();
  get_cached_realtime(&self->last_tick);
  g_atomic_counter_set(&self->ref_cnt, 1);
  self->expire_callback = expire_callback;
  return self;
}

void
_free(CorrelationState *self)
{
  if (self->state)
    g_hash_table_destroy(self->state);
  timer_wheel_free(self->timer_wheel);
  g_mutex_clear(&self->lock);
  g_free(self);
}

CorrelationState *
correlation_state_ref(CorrelationState *self)
{
  g_assert(!self || g_atomic_counter_get(&self->ref_cnt) > 0);

  if (self)
    {
      g_atomic_counter_inc(&self->ref_cnt);
    }
  return self;
}

void
correlation_state_unref(CorrelationState *self)
{
  g_assert(!self || g_atomic_counter_get(&self->ref_cnt));

  if (self && (g_atomic_counter_dec_and_test(&self->ref_cnt)))
    _free(self);
}