/* -*- 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 "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 *
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */

#include "nsStack.h"
#include "nsxpfcCIID.h"
#include "nsxpfcutil.h"

static NS_DEFINE_IID(kISupportsIID, NS_ISUPPORTS_IID);
static NS_DEFINE_IID(kCStackCID, NS_STACK_CID);

nsStack :: nsStack()
{
  NS_INIT_REFCNT();

  mVoidArray = nsnull ;
}

nsStack :: ~nsStack()
{
  DeleteIfObject(mVoidArray) ;
}

NS_IMPL_QUERY_INTERFACE(nsStack, kCStackCID)
NS_IMPL_ADDREF(nsStack)
NS_IMPL_RELEASE(nsStack)

nsresult nsStack :: Init()
{
  mVoidArray = NewObject(nsVoidArray) ;

  return NS_OK ;
}

PRBool nsStack :: Empty()
{
  return (mVoidArray->Count() ? PR_TRUE : PR_FALSE) ;
}

nsresult nsStack :: Push(nsComponent aComponent)
{
  nsresult res = NS_OK;

  if (PR_TRUE == mVoidArray->AppendElement(aComponent))
    return NS_OK ;

  return res ;
}

nsComponent nsStack :: Pop()
{
  nsComponent component = mVoidArray->ElementAt(mVoidArray->Count()-1);

  if (PR_TRUE == mVoidArray->RemoveElementAt(mVoidArray->Count()-1))
    return component ;

  return nsnull ;
}

nsComponent nsStack :: Top()
{
  return (mVoidArray->ElementAt(mVoidArray->Count()-1)) ;
}