/*
 * This file is part of Deliantra, the Roguelike Realtime MMORPG.
 * 
 * Copyright (©) 2007,2008,2009,2010,2011,2012 Marc Alexander Lehmann / Robin Redeker / the Deliantra team
 * 
 * Deliantra is free software: you can redistribute it and/or modify it under
 * the terms of the Affero GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, 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 Affero GNU General Public License
 * and the GNU General Public License along with this program. If not, see
 * <http://www.gnu.org/licenses/>.
 * 
 * The authors can be reached via e-mail to <support@deliantra.net>
 */

#include "global.h"
#include "evthread.h"
#include "cfperl.h"

thread evthread;
static ev_loop *loop;

/////////////////////////////////////////////////////////////////////////////

ev_async tick_watcher;
EV_ATOMIC_T coroapi::cede_pending;

static ev_periodic cede_watcher;

// it is a bit silly to have to use a mutex, but contention
// is basically non-existant, favouring good mutex implementations.
static SMUTEX (evthread_mutex);
static NV next_tick;

NV get_next_tick ()
{
  SMUTEX_LOCK (evthread_mutex);
  NV retval = next_tick;
  SMUTEX_UNLOCK (evthread_mutex);
  return retval;
}

static void
cede_cb (EV_P_ ev_periodic *w, int revents)
{
  SMUTEX_LOCK (evthread_mutex);
  next_tick = w->at;
  SMUTEX_UNLOCK (evthread_mutex);

  coroapi::cede_pending = 1;

  ev_async_send (EV_DEFAULT_UC, &tick_watcher);
}

static void
tick_cb (EV_P_ ev_async *w, int revents)
{
  cfperl_tick ();
}

/////////////////////////////////////////////////////////////////////////////

static SMUTEX(cb_mutex);
static SCOND(cb_done);

static ev_async async_watcher;
static ev_io aio_watcher;

static void
async_cb (EV_P_ ev_async *w, int revents)
{
  CALL_BEGIN (0);
  CALL_CALL ("IO::AIO::poll_cb", G_SCALAR);
  IV reqs = POPi;
  CALL_END;

  SMUTEX_LOCK (cb_mutex);
  SCOND_SIGNAL (cb_done);
  SMUTEX_UNLOCK (cb_mutex);
}

static void
aio_cb (EV_P_ ev_io *w, int revents)
{
  ev_async_send (EV_DEFAULT_UC, &async_watcher);

  coroapi::cede_pending = 1; // to decrease latency

  SCOND_WAIT (cb_done, cb_mutex);
}

/////////////////////////////////////////////////////////////////////////////

static void *
evthread_proc (void *arg)
{
  SMUTEX_LOCK (cb_mutex);

  ev_run (loop, 0);

  return 0;
}

void evthread_start (int aiofd)
{
  I_EV_API ("evthread");

  // main loop
  ev_async_init (&tick_watcher, tick_cb);
  ev_set_priority (&tick_watcher, 1);
  ev_async_start (EV_DEFAULT_UC, &tick_watcher);

  ev_async_init (&async_watcher, async_cb);
  ev_set_priority (&async_watcher, 1);
  ev_async_start (EV_DEFAULT_UC, &async_watcher);

  // secondary loop, we use select/poll as epoll has very
  // bad timing characteristics and we only watch a single low fd.
  loop = ev_loop_new (EVBACKEND_SELECT);

  ev_periodic_init (&cede_watcher, cede_cb, 0, TICK, 0);
  ev_periodic_start (loop, &cede_watcher);

  ev_io_init (&aio_watcher, aio_cb, aiofd, EV_READ);
  ev_io_start (loop, &aio_watcher);

  evthread.start (evthread_proc);
}