pjs/uriloader/base/nsDocLoader.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (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.
 *
 * Contributor(s): 
 */
#include "nsIDocumentLoader.h"
#include "nsIWebShell.h"
#include "prmem.h"
#include "plstr.h"
#include "nsString.h"
#include "nsISupportsArray.h"
#include "nsIURL.h"
#include "nsIStreamListener.h"
#include "nsIFactory.h"
#include "nsIContentViewerContainer.h"
#include "nsIContentViewer.h"
#include "nsITimer.h"
#include "nsIDocumentLoaderObserver.h"
#include "nsVoidArray.h"
#include "nsIServiceManager.h"
#include "nsXPIDLString.h"

#include "nsILoadGroup.h"

#include "nsNetUtil.h"
#include "nsIURL.h"
#include "nsIChannel.h"
#include "nsIHTTPChannel.h"
#include "nsHTTPEnums.h"
#include "nsIDNSService.h"
#include "nsIProgressEventSink.h"

#include "nsIGenericFactory.h"
#include "nsCOMPtr.h"
#include "nsCom.h"
#include "prlog.h"
#include "prprf.h"

#include "nsWeakReference.h"

#include "nsIStreamConverterService.h"
#include "nsIStreamConverter.h"
static NS_DEFINE_CID(kStreamConverterServiceCID, NS_STREAMCONVERTERSERVICE_CID);

#include <iostream.h>

#include "nsIPref.h"
#include "nsIURIContentListener.h"
#include "nsIURILoader.h"
#include "nsCURILoader.h"

// XXX ick ick ick
#include "nsIDocument.h"
#include "nsIPresShell.h"
#include "nsIPresContext.h"

#if defined(PR_LOGGING)
//
// Log module for nsIDocumentLoader logging...
//
// To enable logging (see prlog.h for full details):
//
//    set NSPR_LOG_MODULES=DocLoader:5
//    set NSPR_LOG_FILE=nspr.log
//
// this enables PR_LOG_DEBUG level information and places all output in
// the file nspr.log
//
PRLogModuleInfo* gDocLoaderLog = nsnull;
#endif /* PR_LOGGING */


/* Define IIDs... */
static NS_DEFINE_IID(kIStreamObserverIID,          NS_ISTREAMOBSERVER_IID);
static NS_DEFINE_IID(kIDocumentLoaderIID,          NS_IDOCUMENTLOADER_IID);
static NS_DEFINE_IID(kIDocumentLoaderFactoryIID,   NS_IDOCUMENTLOADERFACTORY_IID);
static NS_DEFINE_IID(kISupportsIID,                NS_ISUPPORTS_IID);
static NS_DEFINE_IID(kIDocumentIID,                NS_IDOCUMENT_IID);
static NS_DEFINE_IID(kIStreamListenerIID,          NS_ISTREAMLISTENER_IID);

static NS_DEFINE_IID(kIContentViewerContainerIID,  NS_ICONTENT_VIEWER_CONTAINER_IID);
static NS_DEFINE_CID(kGenericFactoryCID,           NS_GENERICFACTORY_CID);


/****************************************************************************
 * nsDocLoaderImpl implementation...
 ****************************************************************************/

class nsDocLoaderImpl : public nsIDocumentLoader, 
                        public nsIStreamObserver,
                        public nsSupportsWeakReference
{
public:

    nsDocLoaderImpl();

    nsresult Init(nsDocLoaderImpl* aParent);

    // for nsIGenericFactory:
    static NS_IMETHODIMP Create(nsISupports *aOuter, const nsIID &aIID, void **aResult);

    NS_DECL_ISUPPORTS

    // nsIDocumentLoader interface
    NS_IMETHOD LoadDocument(nsIURI * aUri, 
                            const char *aCommand,
                            nsISupports* aContainer,
                            nsIInputStream* aPostDataStream = nsnull,
                            nsISupports* aExtraInfo = nsnull,
                            nsLoadFlags aType = nsIChannel::LOAD_NORMAL,
                            const PRUint32 aLocalIP = 0,
                            const PRUnichar* aReferrer = nsnull);

    NS_IMETHOD Stop(void);

    NS_IMETHOD IsBusy(PRBool& aResult);

    NS_IMETHOD CreateDocumentLoader(nsIDocumentLoader** anInstance);

    NS_IMETHOD AddObserver(nsIDocumentLoaderObserver *aObserver);
    NS_IMETHOD RemoveObserver(nsIDocumentLoaderObserver *aObserver);

    NS_IMETHOD SetContainer(nsISupports* aContainer);
    NS_IMETHOD GetContainer(nsISupports** aResult);

    // XXX: this method is evil and should be removed.
    NS_IMETHOD GetContentViewerContainer(PRUint32 aDocumentID, 
                                         nsIContentViewerContainer** aResult);

	NS_IMETHOD GetLoadGroup(nsILoadGroup** aResult);

    NS_IMETHOD Destroy();

    // nsIStreamObserver methods: (for observing the load group)
    NS_DECL_NSISTREAMOBSERVER

    // Implementation specific methods...
protected:
    virtual ~nsDocLoaderImpl();

    nsresult RemoveChildGroup(nsDocLoaderImpl *aLoader);
    void DocLoaderIsEmpty(nsresult aStatus);

    void FireOnStartDocumentLoad(nsDocLoaderImpl* aLoadInitiator,
                                 nsIURI* aURL);

    void FireOnEndDocumentLoad(nsDocLoaderImpl* aLoadInitiator,
                               nsIChannel *aDocChannel,
                               nsresult aStatus);
							   
    void FireOnStartURLLoad(nsDocLoaderImpl* aLoadInitiator,
                            nsIChannel* channel, 
                            nsIContentViewer* aViewer);

    void FireOnEndURLLoad(nsDocLoaderImpl* aLoadInitiator,
                          nsIChannel* channel, nsresult aStatus);

protected:

    // IMPORTANT: The ownership implicit in the following member
    // variables has been explicitly checked and set using nsCOMPtr
    // for owning pointers and raw COM interface pointers for weak
    // (ie, non owning) references. If you add any members to this
    // class, please make the ownership explicit (pinkerton, scc).
  
    nsCOMPtr<nsIChannel>       mDocumentChannel;       // [OWNER] ???compare with document
    nsVoidArray                mDocObservers;
    nsISupports*               mContainer;             // [WEAK] it owns me!

    nsDocLoaderImpl*           mParent;                // [WEAK]

    nsCString                  mCommand;

    /*
     * This flag indicates that the loader is loading a document.  It is set
     * from the call to LoadDocument(...) until the OnConnectionsComplete(...)
     * notification is fired...
     */
    PRBool mIsLoadingDocument;

    nsCOMPtr<nsILoadGroup>      mLoadGroup;
    nsCOMPtr<nsISupportsArray>  mChildList;
};


nsDocLoaderImpl::nsDocLoaderImpl()
{
    NS_INIT_REFCNT();

#if defined(PR_LOGGING)
    if (nsnull == gDocLoaderLog) {
        gDocLoaderLog = PR_NewLogModule("DocLoader");
    }
#endif /* PR_LOGGING */

    mContainer = nsnull;
    mParent    = nsnull;

    mIsLoadingDocument = PR_FALSE;

    PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
           ("DocLoader:%p: created.\n", this));
}

nsresult
nsDocLoaderImpl::Init(nsDocLoaderImpl *aParent)
{
    nsresult rv;

    rv = NS_NewLoadGroup(this, getter_AddRefs(mLoadGroup));
    if (NS_FAILED(rv)) return rv;

    PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
           ("DocLoader:%p: load group %x.\n", this, mLoadGroup.get()));

///    rv = mLoadGroup->SetGroupListenerFactory(this);
///    if (NS_FAILED(rv)) return rv;

    rv = NS_NewISupportsArray(getter_AddRefs(mChildList));
    if (NS_FAILED(rv)) return rv;

    mParent = aParent;
    return NS_OK;
}

nsDocLoaderImpl::~nsDocLoaderImpl()
{
		/*
			|ClearWeakReferences()| here is intended to prevent people holding weak references
			from re-entering this destructor since |QueryReferent()| will |AddRef()| me, and the
			subsequent |Release()| will try to destroy me.  At this point there should be only
			weak references remaining (otherwise, we wouldn't be getting destroyed).

			An alternative would be incrementing our refcount (consider it a compressed flag
			saying "Don't re-destroy.").  I haven't yet decided which is better. [scc]
		*/
	ClearWeakReferences();

  Destroy();

  PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
         ("DocLoader:%p: deleted.\n", this));

#ifdef DEBUG
  PRUint32 count=0;
  mChildList->Count(&count);
  NS_PRECONDITION((0 == count), "Document loader has children...");
#endif
}


/*
 * Implementation of ISupports methods...
 */
NS_IMPL_ADDREF(nsDocLoaderImpl);
NS_IMPL_RELEASE(nsDocLoaderImpl);


NS_IMETHODIMP
nsDocLoaderImpl::QueryInterface(REFNSIID aIID, void** aInstancePtr)
{
    if (NULL == aInstancePtr) {
        return NS_ERROR_NULL_POINTER;
    }
    if (aIID.Equals(kIDocumentLoaderIID)) {
        *aInstancePtr = (void*)(nsIDocumentLoader*)this;
        NS_ADDREF_THIS();
        return NS_OK;
    }
    if (aIID.Equals(kIStreamObserverIID)) {
        *aInstancePtr = (void*)(nsIStreamObserver*)this;
        NS_ADDREF_THIS();
        return NS_OK;
    }
    if (aIID.Equals(nsCOMTypeInfo<nsISupportsWeakReference>::GetIID())) {
        *aInstancePtr = NS_STATIC_CAST(nsISupportsWeakReference*,this);
        NS_ADDREF_THIS();
        return NS_OK;        
    }
    return NS_NOINTERFACE;
}

NS_IMETHODIMP
nsDocLoaderImpl::CreateDocumentLoader(nsIDocumentLoader** anInstance)
{
  nsDocLoaderImpl* newLoader = nsnull;
  nsresult rv = NS_OK;

  /* Check for initial error conditions... */
  if (nsnull == anInstance) {
    return NS_ERROR_NULL_POINTER;
  }

  *anInstance = nsnull;
  NS_NEWXPCOM(newLoader, nsDocLoaderImpl);
  if (nsnull == newLoader) {
    return NS_ERROR_OUT_OF_MEMORY;
  }
  //
  // The QI causes the new document laoder to get AddRefed...  So now
  // its refcount is 1.
  //
  rv = newLoader->QueryInterface(kIDocumentLoaderIID, (void**)anInstance);
  if (NS_FAILED(rv)) {
    delete newLoader;
    return rv;
  }

  // Initialize now that we have a reference
  rv = newLoader->Init(this);
  if (NS_SUCCEEDED(rv)) {
    //
    // XXX this method incorrectly returns a bool    
    //
    rv = mChildList->AppendElement((nsIDocumentLoader*)newLoader) 
       ? NS_OK : NS_ERROR_FAILURE;
  }

  // Delete the new document loader if any error occurs during initialization
  if (NS_FAILED(rv)) {
    NS_RELEASE(*anInstance);
  }

  return rv;
}


static NS_DEFINE_CID(kURILoaderCID, NS_URI_LOADER_CID);

NS_IMETHODIMP
nsDocLoaderImpl::LoadDocument(nsIURI * aUri, 
                              const char* aCommand,
                              nsISupports* aContainer,
                              nsIInputStream* aPostDataStream,
                              nsISupports* aExtraInfo,
                              nsLoadFlags aType,
                              const PRUint32 aLocalIP,
                              const PRUnichar* aReferrer)
{
  nsresult rv = NS_ERROR_FAILURE;

  if (aUri) {
    nsXPIDLCString aUrlScheme;
    aUri->GetScheme(getter_Copies(aUrlScheme));

    nsCOMPtr<nsISupports> openContext = do_QueryInterface(mLoadGroup);

    // let's try uri dispatching...
    NS_WITH_SERVICE(nsIURILoader, pURILoader, kURILoaderCID, &rv);
    if (NS_FAILED(rv)) return rv;

    /*
     * Set the flag indicating that the document loader is in the process of
     * loading a document.  This flag will remain set until the 
     * OnConnectionsComplete(...) notification is fired for the loader...
     */
    mIsLoadingDocument = PR_TRUE;

    nsURILoadCommand loadCmd = nsIURILoader::viewNormal;
    if (nsCRT::strcasecmp(aCommand, "view-link-click") == 0)
      loadCmd = nsIURILoader::viewUserClick;
    else if (nsCRT::strcasecmp(aCommand, "view-source") == 0)
      loadCmd = nsIURILoader::viewSource;

    // temporary hack for post data...eventually this snippet of code
    // should be moved into the layout call when callers go through the
    // uri loader directly!

    if (aPostDataStream) {
      // query for private post data stream interface
      nsCOMPtr<nsPIURILoaderWithPostData>  postLoader = do_QueryInterface(pURILoader, &rv);
      if (NS_SUCCEEDED(rv))
        rv = postLoader->OpenURIWithPostData(aUri, 
                                             loadCmd,
                                             nsnull /* window target */,
                                             aContainer,
                                             nsnull /* referring uri */,
                                             aPostDataStream,
                                             mLoadGroup,
                                             getter_AddRefs(openContext));
                                         
    }
    else
      rv = pURILoader->OpenURI(aUri, loadCmd, nsnull /* window target */, 
                               aContainer,
                               nsnull /* refferring URI */, 
                               mLoadGroup, 
                               getter_AddRefs(openContext));

// I think that this is wrong...  Do *not* destroy the loadGroup assosicated
// with a DocLoader if the URI is retargeted!!  The DocLoader does not care.
//
///    if (openContext) {
///      mLoadGroup = do_QueryInterface(openContext);
///    }
  } 

  return rv;
}

NS_IMETHODIMP
nsDocLoaderImpl::Stop(void)
{
  nsresult rv = NS_OK;
  PRUint32 count, i;

  PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
         ("DocLoader:%p: Stop() called\n", this));

  rv = mChildList->Count(&count);
  if (NS_FAILED(rv)) return rv;

  for (i=0; i<count; i++) {
    nsIDocumentLoader* loader;

    loader = NS_STATIC_CAST(nsIDocumentLoader*, mChildList->ElementAt(i));

    if (loader) {
      (void) loader->Stop();
      NS_RELEASE(loader);
    }
  }

  rv = mLoadGroup->Cancel();

  return rv;
}       


NS_IMETHODIMP
nsDocLoaderImpl::IsBusy(PRBool& aResult)
{
  nsresult rv;

  //
  // A document loader is busy if either:
  //
  //   1. It is currently loading a document (ie. one or more URIs)
  //   2. One of it's child document loaders is busy...
  //
  aResult = PR_FALSE;

  /* Is this document loader busy? */
  if (mIsLoadingDocument) {
    rv = mLoadGroup->IsPending(&aResult);
    if (NS_FAILED(rv)) return rv;
  }

  /* Otherwise, check its child document loaders... */
  if (!aResult) {
    PRUint32 count, i;

    rv = mChildList->Count(&count);
    if (NS_FAILED(rv)) return rv;

    for (i=0; i<count; i++) {
      nsIDocumentLoader* loader;

      loader = NS_STATIC_CAST(nsIDocumentLoader*, mChildList->ElementAt(i));

      if (loader) {
        (void) loader->IsBusy(aResult);
        NS_RELEASE(loader);

        if (aResult) break;
      }
    }
  }

  return NS_OK;
}


/*
 * Do not hold refs to the objects in the observer lists.  Observers
 * are expected to remove themselves upon their destruction if they
 * have not removed themselves previously
 */
NS_IMETHODIMP
nsDocLoaderImpl::AddObserver(nsIDocumentLoaderObserver* aObserver)
{
  nsresult rv;

  if (mDocObservers.IndexOf(aObserver) == -1) {
    //
    // XXX this method incorrectly returns a bool    
    //
    rv = mDocObservers.AppendElement(aObserver) ? NS_OK : NS_ERROR_FAILURE;
  } else {
    // The observer is already in the list...
    rv = NS_ERROR_FAILURE;
  }
  return rv;
}

NS_IMETHODIMP
nsDocLoaderImpl::RemoveObserver(nsIDocumentLoaderObserver* aObserver)
{
  if (PR_TRUE == mDocObservers.RemoveElement(aObserver)) {
    return NS_OK;
  }
  return NS_ERROR_FAILURE;
}

NS_IMETHODIMP
nsDocLoaderImpl::SetContainer(nsISupports* aContainer)
{
  // This is a weak reference...
  mContainer = aContainer;

  return NS_OK;
}

NS_IMETHODIMP
nsDocLoaderImpl::GetContainer(nsISupports** aResult)
{
   NS_ENSURE_ARG_POINTER(aResult);

   *aResult = mContainer;
   NS_IF_ADDREF(*aResult);

   return NS_OK;
}

NS_IMETHODIMP
nsDocLoaderImpl::GetLoadGroup(nsILoadGroup** aResult)
{
  nsresult rv = NS_OK;

  if (nsnull == aResult) {
    rv = NS_ERROR_NULL_POINTER;
  } else {
    *aResult = mLoadGroup;
    NS_IF_ADDREF(*aResult);
  }
  return rv;
}

NS_IMETHODIMP
nsDocLoaderImpl::GetContentViewerContainer(PRUint32 aDocumentID,
                                           nsIContentViewerContainer** aResult)
{
  nsISupports* base = (nsISupports*) aDocumentID;
  nsIDocument* doc;
  nsresult rv;

  rv = base->QueryInterface(kIDocumentIID, (void**)&doc);
  if (NS_SUCCEEDED(rv)) {
    nsIPresShell* pres;
    pres = doc->GetShellAt(0);
    if (nsnull != pres) {
      nsIPresContext* presContext;
      rv = pres->GetPresContext(&presContext);
      if (NS_SUCCEEDED(rv) && nsnull != presContext) {
        nsISupports* supp;
        rv = presContext->GetContainer(&supp);
        if (NS_SUCCEEDED(rv) && nsnull != supp) {          
          rv = supp->QueryInterface(kIContentViewerContainerIID, (void**)aResult);          
          NS_RELEASE(supp);
        }
        NS_RELEASE(presContext);
      }
      NS_RELEASE(pres);
    }
    NS_RELEASE(doc);
  }
  return rv;
}

NS_IMETHODIMP
nsDocLoaderImpl::Destroy()
{
    Stop();

  // Remove the document loader from the parent list of loaders...
    if (mParent) {
        mParent->RemoveChildGroup(this);
        mParent = nsnull;
    }

    mDocumentChannel = null_nsCOMPtr();

    // Clear factory pointer (which is the docloader)
    (void)mLoadGroup->SetGroupListenerFactory(nsnull);

    mLoadGroup->SetGroupObserver(nsnull);

    return NS_OK;
}




NS_IMETHODIMP
nsDocLoaderImpl::OnStartRequest(nsIChannel *aChannel, nsISupports *aCtxt)
{
    // called each time a channel is added to the group.
    nsresult rv;

    //
    // Only fire an OnStartDocumentLoad(...) if the document loader
    // has initiated a load...  Otherwise, this notification has
    // resulted from a channel being added to the load group.
    //
    if (mIsLoadingDocument) {
        PRUint32 count;

        rv = mLoadGroup->GetActiveCount(&count);
        if (NS_FAILED(rv)) return rv;

        if (1 == count) {
            nsCOMPtr<nsIURI> uri;

            rv = aChannel->GetURI(getter_AddRefs(uri));
            if (NS_FAILED(rv)) return rv;

            // This channel is associated with the entire document...
            mDocumentChannel = aChannel;
            mLoadGroup->SetDefaultLoadChannel(mDocumentChannel); 
            FireOnStartDocumentLoad(this, uri);
        } 
        else {
          nsCOMPtr<nsIContentViewer> viewer;
          nsCOMPtr<nsIWebShell> webShell(do_QueryInterface(mContainer));
          NS_ENSURE_TRUE(webShell, NS_ERROR_FAILURE);
  
          webShell->GetContentViewer(getter_AddRefs(viewer));

          FireOnStartURLLoad(this, aChannel, viewer);
        }
    }
    return NS_OK;
}

NS_IMETHODIMP
nsDocLoaderImpl::OnStopRequest(nsIChannel *aChannel, 
                               nsISupports *aCtxt, 
                               nsresult aStatus, 
                               const PRUnichar *aMsg)
{
  nsresult rv = NS_OK;

  //
  // Only fire the OnEndDocumentLoad(...) if the document loader 
  // has initiated a load...
  //
  if (mIsLoadingDocument) {
    PRUint32 count;

    rv = mLoadGroup->GetActiveCount(&count);
    if (NS_FAILED(rv)) return rv;

    //
    // The load group for this DocumentLoader is idle...
    //
    if (0 == count) {
      DocLoaderIsEmpty(aStatus);
    } else {
      FireOnEndURLLoad(this, aChannel, aStatus);
    }
  }

  return NS_OK;
}


nsresult nsDocLoaderImpl::RemoveChildGroup(nsDocLoaderImpl* aLoader)
{
  nsresult rv = NS_OK;

  if (NS_SUCCEEDED(rv)) {
    mChildList->RemoveElement((nsIDocumentLoader*)aLoader);
  }
  return rv;
}


void nsDocLoaderImpl::DocLoaderIsEmpty(nsresult aStatus)
{
  if (mParent) { 
      mParent->DocLoaderIsEmpty(aStatus); 
      // 
      // New code to break the circular reference between 
      // the load group and the docloader... 
      // 
      mLoadGroup->SetDefaultLoadChannel(nsnull); 
  } 

  if (mIsLoadingDocument) {
    PRBool busy = PR_FALSE;
    /* In the unimagineably rude circumstance that onload event handlers
       triggered by this function actually kill the window ... ok, it's
       not unimagineable; it's happened ... this deathgrip keeps this object
       alive long enough to survive this function call. */
    nsCOMPtr<nsIDocumentLoader> kungFuDeathGrip(this);

    IsBusy(busy);
    if (!busy) {
      PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
             ("DocLoader:%p: Is now idle...\n", this));

      nsCOMPtr<nsIChannel> docChannel(mDocumentChannel);

      mDocumentChannel = null_nsCOMPtr();
      mIsLoadingDocument = PR_FALSE;

      //
      // Do nothing after firing the OnEndDocumentLoad(...). The document
      // loader may be loading a *new* document - if LoadDocument()
      // was called from a handler!
      //
      FireOnEndDocumentLoad(this, docChannel, aStatus);

      if (mParent) {
        mParent->DocLoaderIsEmpty(aStatus);
      }
    }
  }
}


void nsDocLoaderImpl::FireOnStartDocumentLoad(nsDocLoaderImpl* aLoadInitiator,
                                              nsIURI* aURL)
{
  PRInt32 count;

#if defined(DEBUG)
  char *buffer;

  aURL->GetSpec(&buffer);
  if (aLoadInitiator == this) {
    PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
           ("DocLoader:%p: ++ Firing OnStartDocumentLoad(...).\tURI: %s\n",
            this, buffer));
  } else {
    PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
           ("DocLoader:%p: --   Propagating OnStartDocumentLoad(...)."
            "DocLoader:%p  URI:%s\n", 
            this, aLoadInitiator, buffer));
  }
  nsCRT::free(buffer);
#endif /* DEBUG */

  /*
   * First notify any observers that the document load has begun...
   *
   * Operate the elements from back to front so that if items get
   * get removed from the list it won't affect our iteration
   */
  count = mDocObservers.Count();
  while (count > 0) {
    nsIDocumentLoaderObserver *observer;

    observer = NS_STATIC_CAST(nsIDocumentLoaderObserver*, mDocObservers.ElementAt(--count));

    NS_ASSERTION(observer, "NULL observer found in list.");
    if (! observer) {
      continue;
    }

    observer->OnStartDocumentLoad(aLoadInitiator, aURL, mCommand);
  }

  /*
   * Finally notify the parent...
   */
  if (mParent) {
    mParent->FireOnStartDocumentLoad(aLoadInitiator, aURL);
  }
}

void nsDocLoaderImpl::FireOnEndDocumentLoad(nsDocLoaderImpl* aLoadInitiator,
                                            nsIChannel *aDocChannel,
                                            nsresult aStatus)
									
{
#if defined(DEBUG)
  nsCOMPtr<nsIURI> uri;
  nsresult rv = NS_OK;
  if (aDocChannel)
    rv = aDocChannel->GetURI(getter_AddRefs(uri));
  if (NS_SUCCEEDED(rv)) {
    char* buffer = nsnull;
    if (uri)
      rv = uri->GetSpec(&buffer);
      if (NS_SUCCEEDED(rv) && buffer != nsnull) {
        if (aLoadInitiator == this) {
          PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
                 ("DocLoader:%p: ++ Firing OnEndDocumentLoad(...)"
                  "\tURI: %s Status: %x\n", 
                  this, buffer, aStatus));
        } else {
          PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
                 ("DocLoader:%p: --   Propagating OnEndDocumentLoad(...)."
                  "DocLoader:%p  URI:%s\n", 
                  this, aLoadInitiator, buffer));
        }
        nsCRT::free(buffer);
      }
    }
#endif /* DEBUG */

  /*
   * First notify any observers that the document load has finished...
   *
   * Operate the elements from back to front so that if items get
   * get removed from the list it won't affect our iteration
   */
  PRInt32 count;

  count = mDocObservers.Count();
  while (count > 0) {
    nsIDocumentLoaderObserver *observer;

    observer = NS_STATIC_CAST(nsIDocumentLoaderObserver*, mDocObservers.ElementAt(--count));

    NS_ASSERTION(observer, "NULL observer found in list.");
    if (! observer) {
      continue;
    }

    observer->OnEndDocumentLoad(aLoadInitiator, aDocChannel, aStatus, observer);
  }

  /*
   * Next notify the parent...
   */
  if (mParent) {
    mParent->FireOnEndDocumentLoad(aLoadInitiator, aDocChannel, aStatus);
  }
}


void nsDocLoaderImpl::FireOnStartURLLoad(nsDocLoaderImpl* aLoadInitiator,
                                         nsIChannel* aChannel,
                                         nsIContentViewer* aViewer)
{
#if defined(DEBUG)
  nsCOMPtr<nsIURI> uri;
  nsresult rv = NS_OK;
  if (aChannel)
    rv = aChannel->GetURI(getter_AddRefs(uri));
  if (NS_SUCCEEDED(rv)) {
    char* buffer = nsnull;
    if (uri)
      rv = uri->GetSpec(&buffer);
    if (NS_SUCCEEDED(rv) && buffer != nsnull) {
      if (aLoadInitiator == this) {
        PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
               ("DocLoader:%p: ++ Firing OnStartURLLoad(...)"
                "\tURI: %s Viewer: %x\n", 
                this, buffer, aViewer));
      } else {
        PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
               ("DocLoader:%p: --   Propagating OnStartURLLoad(...)."
                "DocLoader:%p  URI:%s\n", 
                this, aLoadInitiator, buffer));
      }
      nsCRT::free(buffer);
    }
  }
#endif /* DEBUG */

  PRInt32 count;

  /*
   * First notify any observers that the URL load has begun...
   *
   * Operate the elements from back to front so that if items get
   * get removed from the list it won't affect our iteration
   */
  count = mDocObservers.Count();
  while (count > 0) {
    nsIDocumentLoaderObserver *observer;

    observer = NS_STATIC_CAST(nsIDocumentLoaderObserver*, mDocObservers.ElementAt(--count));

    NS_ASSERTION(observer, "NULL observer found in list.");
    if (! observer) {
      continue;
    }

    observer->OnStartURLLoad(aLoadInitiator, aChannel, aViewer);
  }

  /*
   * Finally notify the parent...
   */
  if (mParent) {
    mParent->FireOnStartURLLoad(aLoadInitiator, aChannel, aViewer);
  }
}


void nsDocLoaderImpl::FireOnEndURLLoad(nsDocLoaderImpl* aLoadInitiator,
                                       nsIChannel* aChannel, nsresult aStatus)
{
#if defined(DEBUG)
  nsCOMPtr<nsIURI> uri;
  nsresult rv = NS_OK;
  if (aChannel)
    rv = aChannel->GetURI(getter_AddRefs(uri));
  if (NS_SUCCEEDED(rv)) {
    char* buffer = nsnull;
    if (uri)
      rv = uri->GetSpec(&buffer);
    if (NS_SUCCEEDED(rv) && buffer != nsnull) {
      if (aLoadInitiator == this) {
        PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
               ("DocLoader:%p: ++ Firing OnEndURLLoad(...)"
                "\tURI: %s Status: %x\n", 
                this, buffer, aStatus));
      } else {
        PR_LOG(gDocLoaderLog, PR_LOG_DEBUG, 
               ("DocLoader:%p: --   Propagating OnEndURLLoad(...)."
                "DocLoader:%p  URI:%s\n", 
                this, aLoadInitiator, buffer));
      }
      nsCRT::free(buffer);
    }
  }
#endif /* DEBUG */

  PRInt32 count;

  /*
   * First notify any observers that the URL load has completed...
   *
   * Operate the elements from back to front so that if items get
   * get removed from the list it won't affect our iteration
   */
  count = mDocObservers.Count();
  while (count > 0) {
    nsIDocumentLoaderObserver *observer;

    observer = NS_STATIC_CAST(nsIDocumentLoaderObserver*, mDocObservers.ElementAt(--count));

    NS_ASSERTION(observer, "NULL observer found in list.");
    if (! observer) {
      continue;
    }

    observer->OnEndURLLoad(aLoadInitiator, aChannel, aStatus);
  }

  /*
   * Finally notify the parent...
   */
  if (mParent) {
    mParent->FireOnEndURLLoad(aLoadInitiator, aChannel, aStatus);
  }
}




/*******************************************
 *  nsDocLoaderServiceFactory
 *******************************************/
static nsDocLoaderImpl* gServiceInstance = nsnull;

NS_IMETHODIMP
nsDocLoaderImpl::Create(nsISupports *aOuter, const nsIID &aIID, void **aResult)
{
  nsresult rv;
  nsDocLoaderImpl* inst;

  // Parameter validation...
  if (NULL == aResult) {
    rv = NS_ERROR_NULL_POINTER;
    goto done;
  }
  // Do not support aggregatable components...
  *aResult = NULL;
  if (NULL != aOuter) {
    rv = NS_ERROR_NO_AGGREGATION;
    goto done;
  }

  if (NULL == gServiceInstance) {
    // Create a new instance of the component...
    NS_NEWXPCOM(gServiceInstance, nsDocLoaderImpl);
    if (NULL == gServiceInstance) {
      rv = NS_ERROR_OUT_OF_MEMORY;
      goto done;
    }
  }

  // If the QI fails, the component will be destroyed...
  //
  // Use a local copy so the NS_RELEASE() will not null the global
  // pointer...
  inst = gServiceInstance;

  NS_ADDREF(inst);
  rv = inst->QueryInterface(aIID, aResult);
  if (NS_SUCCEEDED(rv)) {
    rv = inst->Init(nsnull);
  }
  NS_RELEASE(inst);

done:
  return rv;
}

// Entry point to create nsDocLoaderService factory instances...

nsresult NS_NewDocLoaderServiceFactory(nsIFactory** aResult)
{
  nsresult rv = NS_OK;
  nsIGenericFactory* factory;
  rv = nsComponentManager::CreateInstance(kGenericFactoryCID, nsnull, 
                                          nsIGenericFactory::GetIID(),
                                          (void**)&factory);
  if (NS_FAILED(rv)) return rv;

  rv = factory->SetConstructor(nsDocLoaderImpl::Create);
  if (NS_FAILED(rv)) {
      NS_RELEASE(factory);
      return rv;
  }

  *aResult = factory;
  return rv;
}