/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "License"); you may not use this file except in
 * compliance with the License.  You may obtain a copy of the License at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is Mozilla Communicator client code.
 *
 * The Initial Developer of the Original Code is Netscape Communications
 * Corporation.  Portions created by Netscape are Copyright (C) 1998
 * Netscape Communications Corporation.  All Rights Reserved.
 */

#include "nsCOMPtr.h"
#include "nsEventQueue.h"
#include "nsIServiceManager.h"
#include "nsIObserverService.h"
#include "nsString2.h"

// in a real system, these would be members in a header class...
static char *gActivatedNotification = "nsIEventQueueActivated";
static char *gDestroyedNotification = "nsIEventQueueDestroyed";

nsEventQueueImpl::nsEventQueueImpl()
{
  NS_INIT_REFCNT();
  AddRef(); 
  // eventqueue ownership model is a little unusual. it addrefs
  // itself, but when linked into a chain after the head, it releases
  // itself, so when it goes dark and empty (unused) it will be
  // deleted.

  mEventQueue = NULL;
  mYoungerQueue = NULL;
  mElderQueue = NULL;
  mAcceptingEvents = PR_TRUE;
  mCouldHaveEvents = PR_TRUE;
}

nsEventQueueImpl::~nsEventQueueImpl()
{
  Unlink();
  if (mEventQueue != NULL) {
    NotifyObservers(gDestroyedNotification);
    PL_DestroyEventQueue(mEventQueue);
  }
}

NS_IMETHODIMP 
nsEventQueueImpl::Init()
{
  mEventQueue = PL_CreateNativeEventQueue("Thread event queue...", PR_GetCurrentThread());
  NotifyObservers(gActivatedNotification);
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::InitFromPLQueue(PLEventQueue* aQueue)
{
  mEventQueue = aQueue;
  NotifyObservers(gActivatedNotification);
  return NS_OK;
}

/* nsISupports interface implementation... */
NS_IMPL_ISUPPORTS2(nsEventQueueImpl,nsIEventQueue,nsPIEventQueueChain)

/* nsIEventQueue interface implementation... */

NS_IMETHODIMP
nsEventQueueImpl::StopAcceptingEvents()
{
  NS_ASSERTION(mElderQueue, "attempted to disable eldest queue in chain");
  mAcceptingEvents = PR_FALSE;
  CheckForDeactivation();
  return NS_OK;
}

// utility funtion to send observers a notification
void
nsEventQueueImpl::NotifyObservers(const char *aTopic)
{
  nsresult rv;
  nsAutoString topic(aTopic);
  nsISupports *us = NS_STATIC_CAST(nsISupports *,(NS_STATIC_CAST(nsIEventQueue *,this)));

  NS_WITH_SERVICE(nsIObserverService, os, NS_OBSERVERSERVICE_PROGID, &rv);
  if (NS_SUCCEEDED(rv))
    os->Notify(us, topic.GetUnicode(), NULL);
}

NS_IMETHODIMP_(PRStatus)
nsEventQueueImpl::PostEvent(PLEvent* aEvent)
{
  if (!mAcceptingEvents) {
    PRStatus rv = PR_FAILURE;
    NS_ASSERTION(mElderQueue, "event dropped because event chain is dead");
    if (mElderQueue) {
      nsCOMPtr<nsIEventQueue> elder(do_QueryInterface(mElderQueue));
      if (elder)
        rv = elder->PostEvent(aEvent);
    }
    return rv;
  }
  return PL_PostEvent(mEventQueue, aEvent);
}

NS_IMETHODIMP
nsEventQueueImpl::PostSynchronousEvent(PLEvent* aEvent, void** aResult)
{
  if (!mAcceptingEvents) {
    nsresult rv = NS_ERROR_NO_INTERFACE;
    NS_ASSERTION(mElderQueue, "event dropped because event chain is dead");
    if (mElderQueue) {
      nsCOMPtr<nsIEventQueue> elder(do_QueryInterface(mElderQueue));
      if (elder)
        rv = elder->PostSynchronousEvent(aEvent, aResult);
      return rv;
    }
    return NS_ERROR_ABORT;
  }

  void* result = PL_PostSynchronousEvent(mEventQueue, aEvent);
  if (aResult)
    *aResult = result;

  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::EnterMonitor()
{
    PL_ENTER_EVENT_QUEUE_MONITOR(mEventQueue);
    return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::ExitMonitor()
{
    PL_EXIT_EVENT_QUEUE_MONITOR(mEventQueue);
    return NS_OK;
}


NS_IMETHODIMP
nsEventQueueImpl::RevokeEvents(void* owner)
{
    PL_RevokeEvents(mEventQueue, owner);
    return NS_OK;
}


NS_IMETHODIMP
nsEventQueueImpl::GetPLEventQueue(PLEventQueue** aEventQueue)
{
    *aEventQueue = mEventQueue;
    
    if (mEventQueue == NULL)
        return NS_ERROR_NULL_POINTER;

    return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::IsQueueOnCurrentThread(PRBool *aResult)
{
    *aResult = PL_IsQueueOnCurrentThread( mEventQueue );
    return NS_OK;
}


NS_IMETHODIMP
nsEventQueueImpl::ProcessPendingEvents()
{
  PL_ProcessPendingEvents(mEventQueue);
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::EventLoop()
{
  PL_EventLoop(mEventQueue);
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::EventAvailable(PRBool& aResult)
{
  aResult = PL_EventAvailable(mEventQueue);
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::GetEvent(PLEvent** aResult)
{
  *aResult = PL_GetEvent(mEventQueue);
  CheckForDeactivation();
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::HandleEvent(PLEvent* aEvent)
{
  PL_HandleEvent(aEvent);
  return NS_OK;
}

NS_IMETHODIMP_(PRInt32) 
nsEventQueueImpl::GetEventQueueSelectFD() 
{
  return PL_GetEventQueueSelectFD(mEventQueue);
}

NS_METHOD
nsEventQueueImpl::Create(nsISupports *aOuter,
                            REFNSIID aIID,
                            void **aResult)
{
  nsEventQueueImpl* evt = new nsEventQueueImpl();
  if (evt == NULL)
    return NS_ERROR_OUT_OF_MEMORY;
  nsresult rv = evt->QueryInterface(aIID, aResult);
  if (NS_FAILED(rv)) {
    delete evt;
  }
  return rv;
}

// ---------------- nsPIEventQueueChain -----------------

NS_IMETHODIMP
nsEventQueueImpl::AppendQueue(nsIEventQueue *aQueue)
{
  nsresult      rv;
  nsIEventQueue *end;
  nsCOMPtr<nsPIEventQueueChain> queueChain(do_QueryInterface(aQueue));

  if (!aQueue)
    return NS_ERROR_NO_INTERFACE;

/* this would be nice
  NS_ASSERTION(aQueue->mYoungerQueue == NULL && aQueue->mElderQueue == NULL,
               "event queue repeatedly appended to queue chain");
*/
  rv = NS_ERROR_NO_INTERFACE;

  // XXX probably wants a threadlock
  GetYoungest(&end); // addrefs. released by Unlink.
  nsCOMPtr<nsPIEventQueueChain> endChain(do_QueryInterface(end));
  if (endChain) {
    endChain->SetYounger(queueChain);
    queueChain->SetElder(endChain);
    NS_RELEASE(aQueue); // the addref from the constructor
    rv = NS_OK;
  }
  return rv;
}

NS_IMETHODIMP
nsEventQueueImpl::Unlink()
{
  nsPIEventQueueChain *young = mYoungerQueue,
                      *old = mElderQueue;

  // this is probably OK, but for now let's at least know if it happens
  NS_ASSERTION(!mYoungerQueue, "event queue chain broken in middle");

  // break links early in case the Release cascades back onto us
  mYoungerQueue = 0;
  mElderQueue = 0;

  if (young)
    young->SetElder(old);
  if (old) {
    old->SetYounger(young);
    if (!young)
      NS_RELEASE(mElderQueue); // release addref from AppendQueue
  }
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::GetYoungest(nsIEventQueue **aQueue)
{
  if (mYoungerQueue)
    return mYoungerQueue->GetYoungest(aQueue);

  nsIEventQueue *answer = NS_STATIC_CAST(nsIEventQueue *, this);
  NS_ADDREF(answer);
  *aQueue = answer;
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::GetYoungestActive(nsIEventQueue **aQueue)
{
  nsIEventQueue *answer = NULL;

  if (mYoungerQueue)
    mYoungerQueue->GetYoungestActive(&answer);
  if (answer == NULL && mAcceptingEvents && mCouldHaveEvents) {
    answer = NS_STATIC_CAST(nsIEventQueue *, this);
    NS_ADDREF(answer);
  }
  *aQueue = answer;
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::SetYounger(nsPIEventQueueChain *aQueue)
{
  mYoungerQueue = aQueue;
  return NS_OK;
}

NS_IMETHODIMP
nsEventQueueImpl::SetElder(nsPIEventQueueChain *aQueue)
{
  mElderQueue = aQueue;
  return NS_OK;
}