/*

  silcwin32schedule.c

  Author: Pekka Riikonen <priikone@silcnet.org>

  Copyright (C) 2001 Pekka Riikonen

  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.

*/
/* $Id$ */

#include "silcincludes.h"
#includd "silcschedule_i.h"

/* Our "select()" for WIN32. This mimics the behaviour of select() system
   call. It does not call the Winsock's select() though. Its functions
   are derived from GLib's g_poll() and from some old Xemacs's sys_select().

   This makes following assumptions, which I don't know whether they
   are correct or not:

   o SILC_TASK_WRITE is ignored, if set this will return immediately.
   o If all arguments except timeout are NULL then this will register
     a timeout with SetTimer and will wait just for Windows messages
     with WaitMessage.
   o MsgWaitForMultipleObjects is used to wait all kind of events, this
     includes SOCKETs and Windows messages.
   o All Windows messages are dispatched from this function.
   o The Operating System has Winsock 2.

   References:

   o http://msdn.microsoft.com/library/default.asp?
     url=/library/en-us/winui/hh/winui/messques_77zk.asp 
   o http://msdn.microsoft.com/library/default.asp?
     url=/library/en-us/winsock/hh/winsock/apistart_9g1e.asp
   o http://msdn.microsoft.com/library/default.asp?
     url=/library/en-us/dnmgmt/html/msdn_getpeek.asp
   o http://developer.novell.com/support/winsock/doc/toc.htm

*/

int silc_select(SilcScheduleFd fds, uint32 fds_count, struct timeval *timeout)
{
  HANDLE handles[MAXIMUM_WAIT_OBJECTS];
  DWORD ready, curtime, timeo;
  int nhandles = 0, i;
  MSG msg;

  if (fds_count > MAXIMUM_WAIT_OBJECTS)
    fds_count = MAXIMUM_WAIT_OBJECTS;

  for (i = 0; i < fds_count; i++) {
    if (!fds[i].events)
      continue;

    if (fds[i].events & SILC_TASK_READ)
      handles[nhandles++] = (HANDLE)i;

    if (fds[i].events & SILC_TASK_WRITE)
      return 1;

    fds[i].revents = 0;
  }

  timeo = (timeout ? (timeout->tv_sec * 1000) + (timeout->tv_usec / 1000) :
	   INFINITE);

  /* If we have nothing to wait and timeout is set then register a timeout
     and wait just for windows messages. */
  if (nhandles == 0 && timeout) {
    UINT timer = SetTimer(NULL, 0, timeo, NULL);
    curtime = GetTickCount();
    while (timer) {
      WaitMessage();

      while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
	if (msg.message == WM_TIMER) {
	  KillTimer(NULL, timer);
	  return 0;
	}
	TranslateMessage(&msg); 
	DispatchMessage(&msg); 
      }

      KillTimer(NULL, timer);
      if (timeo != INFINITE) {
	timeo -= GetTickCount() - curtime;
	if (timeo < 0)
	  timeo = 0;
      }
      timer = SetTimer(NULL, 0, timeo, NULL);
    }
  }

 retry:
  curtime = GetTickCount();
  ready = MsgWaitForMultipleObjects(nhandles, handles, FALSE, timeo, 
				    QS_ALLINPUT);

  if (ready == WAIT_FAILED) {
    /* Wait failed with error */
    SILC_LOG_WARNING(("WaitForMultipleObjects() failed"));
    return -1;
  } else if (ready >= WAIT_ABANDONED_0 &&
	     ready < WAIT_ABANDONED_0 + nhandles) {
    /* Signal abandoned */
    SILC_LOG_WARNING(("WaitForMultipleObjects() failed (ABANDONED)"));
    return -1;
  } else if (ready == WAIT_TIMEOUT) {
    /* Timeout */
    return 0;
  } else if (ready == WAIT_OBJECT_0 + nhandles) {
    /* Windows messages. The MSDN online says that if the application
       creates a window then its main loop (and we're assuming that
       it is our SILC Scheduler) must handle the Windows messages, so do
       it here as the MSDN suggests. */
    while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
      TranslateMessage(&msg); 
      DispatchMessage(&msg); 
    }

    /* If timeout is set then we must update the timeout since we won't
       return and we will give the wait another try. */
    if (timeo != INFINITE) {
      timeo -= GetTickCount() - curtime;
      if (timeo < 0)
	timeo = 0;
    }

    /* Give the wait another try */
   goto retry;
  } else if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles &&
	     readfds) {
    /* Some other event, like SOCKET or something. */

    /* Go through all fds even though only one was set. This is to avoid
       starvation of high numbered fds. */
    ready -= WAIT_OBJECT_0;
    do {
      for (i = 0; i < fds_count; i++) {
	if (!fds[i].events)
	  continue;
	
	if (fds[i].fd == (int)handles[ready]) {
	  fds[i].revents |= SILC_TASK_READ;
	  break;
	}
      }

      /* Check the status of the next handle and set its fd to the fd
	 set if data is available. */
      while (++ready < fds_count)
	if (WaitForSingleObject(handles[ready], 0) == WAIT_OBJECT_0)
	  break;
    } while (ready < fds_count);

    return i + 1;
  }

  return -1;
}

#ifdef SILC_THREADS

/* Internal wakeup context. */
typedef struct {
  HANDLE wakeup_sema;
  SilcTask wakeup_task;
} *SilcWin32Wakeup;

SILC_TASK_CALLBACK(silc_schedule_wakeup_cb)
{
  /* Nothing */
}

#endif /* SILC_THREADS */

/* Initializes the wakeup of the scheduler. In multi-threaded environment
   the scheduler needs to be wakenup when tasks are added or removed from
   the task queues. This will initialize the wakeup for the scheduler.
   Any tasks that needs to be registered must be registered to the `queue'.
   It is guaranteed that the scheduler will automatically free any
   registered tasks in this queue. This is system specific routine. */

void *silc_schedule_wakeup_init(SilcSchedule schedule)
{
#ifdef SILC_THREADS
  SilcWin32Wakeup wakeup;

  wakeup = silc_calloc(1, sizeof(*wakeup));

  wakeup->wakeup_sema = CreateSemaphore(NULL, 0, 100, NULL);
  if (!wakeup->wakeup_sema) {
    silc_free(wakeup);
    return NULL;
  }

  wakeup->wakeup_task = 
    silc_schedule_task_add(schedule, (int)wakeup->wakeup_sema,
			   silc_schedule_wakeup_cb, wakeup,
			   0, 0, SILC_TASK_FD, 
			   SILC_TASK_PRI_NORMAL);
  if (!wakeup->wakeup_task) {
    CloseHandle(wakeup->wakeup_sema);
    silc_free(wakeup);
    return NULL;
  }

  return (void *)wakeup;
#else
  return NULL;
#endif
}

/* Uninitializes the system specific wakeup. */

void silc_schedule_wakeup_uninit(void *context)
{
#ifdef SILC_THREADS
  SilcWin32Wakeup wakeup = (SilcWin32Wakeup)context;

  if (!wakeup)
    return;

  CloseHandle(wakeup->wakeup_sema);
  silc_free(wakeup);
#endif
}

/* Wakes up the scheduler */

void silc_schedule_wakeup_internal(void *context)
{
#ifdef SILC_THREADS
  SilcWin32Wakeup wakeup = (SilcWin32Wakeup)context;

  if (!wakeup)
    return;

  ReleaseSemaphore(wakeup->wakeup_sema, 1, NULL);
#endif
}