content: /*
   * $Header$
   * $Revision$
   * $Date$
   *
   * ====================================================================
   *
   * 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/>.
   * 
   * $Id$
   */
  
  
  
  package org.jaxen.util;
  
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.NoSuchElementException;
  
  import org.jaxen.JaxenConstants;
  import org.jaxen.Navigator;
  import org.jaxen.UnsupportedAxisException;
  
  /**
   * 
   * Represents the XPath <code>preceding-sibling</code> axis. 
   * The "<code>preceding-sibling</code> axis contains all the
   * preceding siblings of the context node; if the context node is an
   * attribute node or namespace node, the <code>preceding-sibling</code>
   * axis is empty."
   * 
   * @version 1.2b12
   *
   */
  public class PrecedingSiblingAxisIterator implements Iterator
  {
      private Object    contextNode;
      private Navigator navigator;
  
      private Iterator  siblingIter;
      private Object    nextObj;
  
      /**
       * Create a new <code>preceding-sibling</code> axis iterator.
       * 
       * @param contextNode the node to start from
       * @param navigator the object model specific navigator
       */
      public PrecedingSiblingAxisIterator(Object contextNode,
                                          Navigator navigator) throws UnsupportedAxisException
      {
          this.contextNode = contextNode;
          this.navigator   = navigator;
  
          init();
          if ( siblingIter.hasNext() )
          {
              this.nextObj = siblingIter.next();
          }
      }
  
      private void init() throws UnsupportedAxisException
      {
          
          Object parent = this.navigator.getParentNode( this.contextNode );
  
          if ( parent != null )
          {
              Iterator childIter = this.navigator.getChildAxisIterator( parent );
              LinkedList siblings = new LinkedList();
              
              while ( childIter.hasNext() )
              {
                  Object eachChild = childIter.next();
                  if ( eachChild.equals(this.contextNode) )
                  {
                      break;
                  }
                  siblings.addFirst( eachChild );
              }
              
              this.siblingIter = siblings.iterator();
              
          }
          else {
              this.siblingIter = JaxenConstants.EMPTY_ITERATOR;
          }
          
      }
  
      /**
       * Returns true if there are any preceding siblings remaining; false otherwise.
       * 
       * @return true if any preceding siblings remain; false otherwise
       * 
       * @see java.util.Iterator#hasNext()
       */
      public boolean hasNext()
      {
          return ( this.nextObj != null );
      }
  
      /**
       * Returns the next preceding sibling.
       * 
       * @return the next preceding sibling
       * 
       * @throws NoSuchElementException if no preceding siblings remain
       * 
       * @see java.util.Iterator#next()
       */
      public Object next() throws NoSuchElementException
      {
          if ( ! hasNext() )
          {
              throw new NoSuchElementException();
          }
  
          Object obj = this.nextObj;
          if ( siblingIter.hasNext() )
          {
              this.nextObj = siblingIter.next();
          }
          else {
              this.nextObj = null;
          }
          return obj;
      }
  
      /**
       * This operation is not supported.
       * 
       * @throws UnsupportedOperationException
       */
      public void remove() throws UnsupportedOperationException
      {
          throw new UnsupportedOperationException();
      }
  
  }
  