/*

  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/util/StackedIterator.java,v 1.12 2006/02/05 21:47:40 elharo Exp $

  * $Revision: 1.12 $

  * $Date: 2006/02/05 21:47:40 $

  *

  * ====================================================================

  *

  * Copyright 2000-2002 bob mcwhirter & James Strachan.

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions are

  * met:

  * 

  *   * Redistributions of source code must retain the above copyright

  *     notice, this list of conditions and the following disclaimer.

  * 

  *   * 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.

  * 

  *   * Neither the name of the Jaxen Project nor the names of its

  *     contributors may be used to endorse or promote products derived 

  *     from this software without specific prior written permission.

  * 

  * 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 OWNER

  * 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.

  *

  * ====================================================================

  * This software consists of voluntary contributions made by many 

  * individuals on behalf of the Jaxen Project and was originally 

  * created by bob mcwhirter <bob@werken.com> and 

  * James Strachan <jstrachan@apache.org>.  For more information on the 

  * Jaxen Project, please see <http://www.jaxen.org/>.

  * 

  * $Id: StackedIterator.java,v 1.12 2006/02/05 21:47:40 elharo Exp $

  */

 package org.jaxen.util;

 import java.util.HashSet;

 import java.util.Iterator;

 import java.util.LinkedList;

 import java.util.NoSuchElementException;

 import java.util.Set;

 import org.jaxen.Navigator;

 /**

  * @deprecated this iterator is no longer used to implement any of the Jaxen axes. If you have implemented

  * a navigator-specific axis based on this class, take a look at the DescendantAxisIterator for ideas 

  * on how to remove that dependency.

  */

 public abstract class StackedIterator implements Iterator

 {

     private LinkedList iteratorStack;

     private Navigator  navigator;

     private Set        created;

     public StackedIterator(Object contextNode,

                            Navigator navigator)

     {

         this.iteratorStack = new LinkedList();

         this.created       = new HashSet();

         init( contextNode,

               navigator );

     }

     protected StackedIterator()

     {

         this.iteratorStack = new LinkedList();

         this.created       = new HashSet();

     }

     protected void init(Object contextNode,

                         Navigator navigator)

     {

         this.navigator     = navigator;

         //pushIterator( internalCreateIterator( contextNode ) );

     }

     protected Iterator internalCreateIterator(Object contextNode)

     {

         if ( this.created.contains( contextNode ) )

         {

             return null;

         }

         this.created.add( contextNode );

         return createIterator( contextNode );

     }

     public boolean hasNext()

     {

         Iterator curIter = currentIterator();

         if ( curIter == null )

         {

             return false;

         }

         return curIter.hasNext();

     }

     public Object next() throws NoSuchElementException

     {

         if ( ! hasNext() )

         {

             throw new NoSuchElementException();

         }

         Iterator curIter = currentIterator();

         Object   object  = curIter.next();

         pushIterator( internalCreateIterator( object ) );

         return object;

     }

     public void remove() throws UnsupportedOperationException

     {

         throw new UnsupportedOperationException();

     }

     abstract protected Iterator createIterator(Object contextNode);

     protected void pushIterator(Iterator iter)

     {

         if ( iter != null )

         {

             this.iteratorStack.addFirst(iter); //addLast( iter );

         }

     }

     private Iterator currentIterator()

     {

         while ( iteratorStack.size() > 0 )

         {

             Iterator curIter = (Iterator) iteratorStack.getFirst();

             if ( curIter.hasNext() )

             {

                 return curIter;

             }

             iteratorStack.removeFirst();

         }

         return null;

     }

     protected Navigator getNavigator()

     {

         return this.navigator;

     }

 }