/*
Serval Distributed Numbering Architecture (DNA)
Copyright (C) 2012 Paul Gardner-Stephen
 
This program 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
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 GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

/*
  Portions Copyright (C) 2013 Petter Reinholdtsen
  Some rights reserved

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.
*/

#include "fdqueue.h"
#include "conf.h"
#include "str.h"
#include "strbuf.h"
#include "strbuf_helpers.h"

#define MAX_WATCHED_FDS 128
struct pollfd fds[MAX_WATCHED_FDS];
int fdcount=0;
struct sched_ent *fd_callbacks[MAX_WATCHED_FDS];
struct sched_ent *next_alarm=NULL;
struct sched_ent *next_deadline=NULL;
struct profile_total poll_stats={NULL,0,"Idle (in poll)",0,0,0,0};

#define alloca_alarm_name(alarm) ((alarm)->stats ? alloca_str_toprint((alarm)->stats->name) : "Unnamed")

void list_alarms()
{
  DEBUG("Alarms;");
  time_ms_t now = gettime_ms();
  struct sched_ent *alarm;
  
  for (alarm = next_deadline; alarm; alarm = alarm->_next)
    DEBUGF("%p %s deadline in %"PRId64"ms", alarm->function, alloca_alarm_name(alarm), alarm->deadline - now);
  
  for (alarm = next_alarm; alarm; alarm = alarm->_next)
    DEBUGF("%p %s in %"PRId64"ms, deadline in %"PRId64"ms", alarm->function, alloca_alarm_name(alarm), alarm->alarm - now, alarm->deadline - now);
  
  DEBUG("File handles;");
  int i;
  for (i = 0; i < fdcount; ++i)
    DEBUGF("%s watching #%d", alloca_alarm_name(fd_callbacks[i]), fds[i].fd);
}

int deadline(struct sched_ent *alarm)
{
  struct sched_ent *node = next_deadline, *last = NULL;
  if (alarm->deadline < alarm->alarm)
    alarm->deadline = alarm->alarm;
  
  while(node!=NULL){
    if (node->deadline > alarm->deadline)
      break;
    last = node;
    node = node->_next;
  }
  if (last == NULL){
    next_deadline = alarm;
  }else{
    last->_next = alarm;
  }
  alarm->_prev = last;
  if(node!=NULL)
    node->_prev = alarm;
  alarm->_next = node;
  return 0;
}

int is_scheduled(const struct sched_ent *alarm)
{
  return alarm->_next || alarm->_prev || alarm == next_alarm || alarm == next_deadline;
}

// add an alarm to the list of scheduled function calls.
// simply populate .alarm with the absolute time, and .function with the method to call.
// on calling .poll.revents will be zero.
int _schedule(struct __sourceloc __whence, struct sched_ent *alarm)
{
  time_ms_t now = gettime_ms();
  if (config.debug.io)
    DEBUGF("schedule(alarm=%s) alarm=%.3f deadline=%.3f",
	  alloca_alarm_name(alarm),
	  (double)(alarm->alarm - now) / 1000,
	  (double)(alarm->deadline - now) / 1000
	);
  if (!alarm->stats)
    WARN("schedule() called without supplying an alarm name");

  struct sched_ent *node = next_alarm, *last = NULL;
  
  if (is_scheduled(alarm))
    FATAL("Scheduling an alarm that is already scheduled");
  
  if (!alarm->function)
    return WHY("Can't schedule if you haven't set the function pointer");

  // don't bother to schedule an alarm that will (by definition) never run
  if (alarm->alarm == TIME_MS_NEVER_WILL)
    return 0;

  if (alarm->deadline < alarm->alarm)
    alarm->deadline = alarm->alarm;
  
  if (now - alarm->deadline > 1000){
    // 1000ms ago? thats silly, if you keep doing it noone else will get a turn.
    FATALF("Alarm %s tried to schedule a deadline %"PRId64"ms ago",
	   alloca_alarm_name(alarm),
           (now - alarm->deadline)
	);
  }

  // if the alarm has already expired, move straight to the deadline queue
  if (alarm->alarm <= now)
    return deadline(alarm);
  
  while(node!=NULL){
    if (node->alarm > alarm->alarm)
      break;
    last = node;
    node = node->_next;
  }
  if (last == NULL){
    next_alarm = alarm;
  }else{
    last->_next=alarm;
  }
  alarm->_prev = last;
  if(node!=NULL)
    node->_prev = alarm;
  alarm->_next = node;
  
  return 0;
}

// remove a function from the schedule before it has fired
// safe to unschedule twice...
int _unschedule(struct __sourceloc __whence, struct sched_ent *alarm)
{
  if (config.debug.io)
    DEBUGF("unschedule(alarm=%s)", alloca_alarm_name(alarm));

  struct sched_ent *prev = alarm->_prev;
  struct sched_ent *next = alarm->_next;
  
  if (prev)
    prev->_next = next;
  else if(next_alarm==alarm)
    next_alarm = next;
  else if(next_deadline==alarm)
    next_deadline = next;
  
  if (next)
    next->_prev = prev;
  
  alarm->_prev = NULL;
  alarm->_next = NULL;
  return 0;
}

// start watching a file handle, call this function again if you wish to change the event mask
int _watch(struct __sourceloc __whence, struct sched_ent *alarm)
{
  if (config.debug.io)
    DEBUGF("watch(alarm=%s)", alloca_alarm_name(alarm));
  if (!alarm->stats)
    WARN("watch() called without supplying an alarm name");

  if (!alarm->function)
    FATAL("Can't watch if you haven't set the function pointer");
  if (!alarm->poll.events)
    FATAL("Can't watch if you haven't set any poll flags");
  
  if (alarm->_poll_index>=0 && fd_callbacks[alarm->_poll_index]==alarm){
    // updating event flags
    if (config.debug.io)
      DEBUGF("Updating watch %s, #%d for %s", alloca_alarm_name(alarm), alarm->poll.fd, alloca_poll_events(alarm->poll.events));
  }else{
    if (config.debug.io)
      DEBUGF("Adding watch %s, #%d for %s", alloca_alarm_name(alarm), alarm->poll.fd, alloca_poll_events(alarm->poll.events));
    if (fdcount>=MAX_WATCHED_FDS)
      return WHY("Too many file handles to watch");
    fd_callbacks[fdcount]=alarm;
    alarm->poll.revents = 0;
    alarm->_poll_index=fdcount;
    fdcount++;
  }
  fds[alarm->_poll_index]=alarm->poll;
  return 0;
}

int is_watching(struct sched_ent *alarm)
{
  if (alarm->_poll_index <0 || fds[alarm->_poll_index].fd!=alarm->poll.fd)
    return 0;
  return 1;
}

// stop watching a file handle
int _unwatch(struct __sourceloc __whence, struct sched_ent *alarm)
{
  if (config.debug.io)
    DEBUGF("unwatch(alarm=%s)", alloca_alarm_name(alarm));

  int index = alarm->_poll_index;
  if (index <0 || fds[index].fd!=alarm->poll.fd)
    return WHY("Attempted to unwatch a handle that is not being watched");
  
  fdcount--;
  if (index!=fdcount){
    // squash fds
    fds[index] = fds[fdcount];
    fd_callbacks[index] = fd_callbacks[fdcount];
    fd_callbacks[index]->_poll_index=index;
  }
  fds[fdcount].fd=-1;
  fd_callbacks[fdcount]=NULL;
  alarm->_poll_index=-1;
  if (config.debug.io)
    DEBUGF("%s stopped watching #%d for %s", alloca_alarm_name(alarm), alarm->poll.fd, alloca_poll_events(alarm->poll.events));
  return 0;
}

static void call_alarm(struct sched_ent *alarm, int revents)
{
  IN();
  if (!alarm)
    FATAL("Attempted to call with no alarm");
  struct call_stats call_stats;
  call_stats.totals = alarm->stats;
  
  if (config.debug.io)
    DEBUGF("Calling alarm/callback %p %s", alarm, alloca_alarm_name(alarm));

  if (call_stats.totals)
    fd_func_enter(__HERE__, &call_stats);
  
  alarm->poll.revents = revents;
  alarm->function(alarm);
  
  if (call_stats.totals)
    fd_func_exit(__HERE__, &call_stats);

  if (config.debug.io)
    DEBUGF("Alarm %p returned",alarm);

  OUT();
}

int fd_poll()
{
  IN();
  int i, r=0;
  time_ms_t ms=60000;
  time_ms_t now = gettime_ms();
  
  if (!next_alarm && !next_deadline && fdcount==0)
    RETURN(0);
  
  /* move alarms that have elapsed to the deadline queue */
  while (next_alarm!=NULL&&next_alarm->alarm <=now){
    struct sched_ent *alarm = next_alarm;
    unschedule(alarm);
    deadline(alarm);
  }
  
  /* work out how long we can block in poll */
  if (next_deadline)
    ms = 0;
  else if (next_alarm){
    ms = next_alarm->alarm - now;
  }
  
  /* Make sure we don't have any silly timeouts that will make us wait forever. */
  if (ms<0) ms=0;
  
  /* check if any file handles have activity */
  {
    struct call_stats call_stats;
    call_stats.totals=&poll_stats;
    fd_func_enter(__HERE__, &call_stats);
    if (fdcount==0){
      if (ms)
	sleep_ms(ms);
    }else{
      r = poll(fds, fdcount, ms);
      if (config.debug.io) {
	strbuf b = strbuf_alloca(1024);
	int i;
	for (i = 0; i < fdcount; ++i) {
	  if (i)
	    strbuf_puts(b, ", ");
	  strbuf_sprintf(b, "%d:", fds[i].fd);
	  strbuf_append_poll_events(b, fds[i].events);
	  strbuf_puts(b, "->");
	  strbuf_append_poll_events(b, fds[i].revents);
	}
	DEBUGF("poll(fds=(%s), fdcount=%d, ms=%d) -> %d", strbuf_str(b), fdcount, ms, r);
      }
    }
    fd_func_exit(__HERE__, &call_stats);
    now=gettime_ms();
  }

  // Reading new data takes priority over everything else
  // Are any handles marked with POLLIN?
  int in_count=0;
  if (r>0){
    for (i=0;i<fdcount;i++)
      if (fds[i].revents & POLLIN)
        in_count++;
  }

  /* call one alarm function, but only if its deadline time has elapsed OR there is no incoming file activity */
  if (next_deadline && (next_deadline->deadline <=now || (in_count==0))){
    struct sched_ent *alarm = next_deadline;
    unschedule(alarm);
    call_alarm(alarm, 0);
    now=gettime_ms();

    // after running a timed alarm, unless we already know there is data to read we want to check for more incoming IO before we send more outgoing.
    if (in_count==0)
      RETURN(1);
  }
  
  /* If file descriptors are ready, then call the appropriate functions */
  if (r>0) {
    for(i=fdcount -1;i>=0;i--){
      if (fd_callbacks[i] && fd_callbacks[i]->poll.fd == fds[i].fd && fds[i].revents) {
        // if any handles have POLLIN set, don't process any other handles
        if (!(fds[i].revents&POLLIN || in_count==0))
          continue;

	int fd = fds[i].fd;
	/* Call the alarm callback with the socket in non-blocking mode */
	errno=0;
	set_nonblock(fd);
	// Work around OSX behaviour that doesn't set POLLERR on 
	// devices that have been deconfigured, e.g., a USB serial adapter
	// that has been removed.
	if (errno == ENXIO) fds[i].revents|=POLLERR;
	call_alarm(fd_callbacks[i], fds[i].revents);
	/* The alarm may have closed and unwatched the descriptor, make sure this descriptor still matches */
	if (i<fdcount && fds[i].fd == fd){
	  if (set_block(fds[i].fd))
	    FATALF("Alarm %p %s has a bad descriptor that wasn't closed!", fd_callbacks[i], alloca_alarm_name(fd_callbacks[i]));
	}
      }
    }
  }
  RETURN(1);
  OUT();
}