/* Quagga Pthreads support -- header
 * Copyright (C) 2009 Chris Hall (GMCH), Highwayman
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra 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; either version 2, or (at your
 * option) any later version.
 *
 * GNU Zebra 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 GNU Zebra; see the file COPYING.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <zebra.h>

#include "qpnexus.h"
#include "memory.h"
#include "thread.h"
#include "sigevent.h"

/* prototypes */
static void* qpn_start(void* arg);
static void qpn_in_thread_init(qpn_nexus qpn);

/*==============================================================================
 * Quagga Nexus Interface -- qpn_xxxx
 *

 */

/* Initialise a nexus -- allocating it if required.
 *
 * If main_thread is set then no new thread will be created
 * when qpn_exec() is called, instead the finite state machine will be
 * run in the calling thread.  The main thread will only block the
 * message queue's signal.  Non-main threads will block most signals.
 *
 * Returns the qpn_nexus.
 */
qpn_nexus
qpn_init_new(qpn_nexus qpn, int main_thread)
{
  if (qpn == NULL)
    qpn = XCALLOC(MTYPE_QPN_NEXUS, sizeof(struct qpn_nexus)) ;
  else
    memset(qpn, 0,  sizeof(struct qpn_nexus)) ;

  qpn->selection = qps_selection_init_new(qpn->selection);
  qpn->pile = qtimer_pile_init_new(qpn->pile);
  qpn->queue = mqueue_init_new(qpn->queue, mqt_signal_unicast);
  qpn->main_thread = main_thread;
  qpn->start = qpn_start;

  return qpn;
}

/* free timers, selection, message queue and nexus
 * return NULL
 */
qpn_nexus
qpn_free(qpn_nexus qpn)
{
  qps_file qf;
  qtimer qtr;

  if (qpn == NULL)
    return NULL;

  /* timers and the pile */
  if (qpn->pile != NULL)
    {
      while ((qtr = qtimer_pile_ream(qpn->pile, 1)))
          qtimer_free(qtr);
    }

  /* files and selection */
  if (qpn->selection != NULL)
    {
      while ((qf = qps_selection_ream(qpn->selection, 1)))
          qps_file_free(qf);
    }

  /* TODO: free qpn->queue */
  /* TODO: free qpn->mts */


  XFREE(MTYPE_QPN_NEXUS, qpn) ;

  return NULL;
}

/* If not main thread create new qpthread.
 * Execute the state machine */
void
qpn_exec(qpn_nexus qpn)
{
  if (qpn->main_thread)
    {
      /* Run the state machine in calling thread */
      qpn->start(qpn);
    }
  else
    {
      /* create a qpthread and run the state machine in it */
      qpt_thread_create(qpn->start, qpn, NULL) ;
    }
}

/*==============================================================================
 * Pthread routine
 *
 * Processes:
 *
 *   1) Main thread only -- signals.
 *
 *   2) Pending work -- event hooks.
 *
 *   3) messages coming from other pthreads -- mqueue_queue.
 *
 *   4) I/O -- qpselect
 *
 *      This deals with all active sockets for read/write/connect/accept.
 *
 *      Each time a socket is readable, one message is read and dispatched.
 *      The pselect timeout is set to be when the next timer is due.
 *
 *   5) Timers -- qtimers
 *
 *   6) Legacy threads.  To deal with legacy timer mechanism.
 *
 *
 */
static void*
qpn_start(void* arg)
{
  qpn_nexus qpn = arg;
  mqueue_block mqb;
  int actions;
  qtime_mono_t now;
  qtime_mono_t max_wait;
  int i;

  /* now in our thread, complete initialisation */
  qpn_in_thread_init(qpn);

  while (!qpn->terminate)
    {
      /* Signals are highest priority.
       * only execute on the main thread */
      if (qpn->main_thread)
        quagga_sigevent_process ();

      /* max time to wait in pselect */
      now = qt_get_monotonic();
      max_wait = now + QTIME(MAX_PSELECT_TIMOUT);

      /* event hooks, if any */
      for (i = 0; i < NUM_EVENT_HOOK; ++i)
        {
          if (qpn->event_hook[i] != NULL)
            {
              qtime_mono_t event_wait = qpn->event_hook[i]();
              if (event_wait > 0 && event_wait < max_wait)
                max_wait = event_wait;
            }
        }

      /* drain the message queue, will be in waiting for signal state
       * when it's empty */
      for (;;)
        {
          mqb = mqueue_dequeue(qpn->queue, 1, qpn->mts) ;
          if (mqb == NULL)
            break;

          mqb_dispatch(mqb, mqb_action);
        }

      /* block for some input, output, signal or timeout */
      actions = qps_pselect(qpn->selection,
          qtimer_pile_top_time(qpn->pile, max_wait));

      /* process I/O actions */
      while (actions)
          actions = qps_dispatch_next(qpn->selection) ;

      mqueue_done_waiting(qpn->queue, qpn->mts);

      /* process timers */
      now = qt_get_monotonic();
      while (qtimer_pile_dispatch_next(qpn->pile, now))
        {
        }
    }

  /* last bit of code to run in this thread */
  if (qpn->in_thread_final)
    qpn->in_thread_final();

  return NULL;
}

/* Now running in our thread, complete initialisation */
static void
qpn_in_thread_init(qpn_nexus qpn)
{
  sigset_t newmask;

  qpn->thread_id = qpt_thread_self();

  if (qpn->main_thread)
    {
      /* Main thread, block the message queue's signal */
      sigemptyset (&newmask);
      sigaddset (&newmask, SIGMQUEUE);
    }
  else
    {
      /*
       * Not main thread.  Block most signals, but be careful not to
       * defer SIGTRAP because doing so breaks gdb, at least on
       * NetBSD 2.0.  Avoid asking to block SIGKILL, just because
       * we shouldn't be able to do so.  Avoid blocking SIGFPE,
       * SIGILL, SIGSEGV, SIGBUS as this is undefined by POSIX.
       * Don't block SIGPIPE so that is gets ignored on this thread.
       */
      sigfillset (&newmask);
      sigdelset (&newmask, SIGTRAP);
      sigdelset (&newmask, SIGKILL);
      sigdelset (&newmask, SIGPIPE);
      sigdelset (&newmask, SIGFPE);
      sigdelset (&newmask, SIGILL);
      sigdelset (&newmask, SIGSEGV);
      sigdelset (&newmask, SIGBUS);
    }

  if (qpthreads_enabled)
    qpt_thread_sigmask(SIG_BLOCK, &newmask, NULL);
  else
    {
      if (sigprocmask(SIG_BLOCK, &newmask, NULL) != 0)
        zabort_errno("sigprocmask failed") ;
    }

  /* Now we have thread_id and mask, prep for using message queue. */
  if (qpn->queue != NULL)
    qpn->mts = mqueue_thread_signal_init(qpn->mts, qpn->thread_id, SIGMQUEUE);
  if (qpn->selection != NULL)
    qps_set_signal(qpn->selection, SIGMQUEUE, newmask);

  /* custom in-thread initialization */
  if (qpn->in_thread_init != NULL)
    qpn->in_thread_init();
}

/* Ask the thread to terminate itself quickly and cleanly */
void
qpn_terminate(qpn_nexus qpn)
{
  qpn->terminate = 1;
  /* wake up any pselect */
  qpt_thread_signal(qpn->thread_id, SIGMQUEUE);
}