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;
  
  import java.util.Iterator;
  
  import org.jaxen.pattern.Pattern;
  import org.jaxen.util.AncestorAxisIterator;
  import org.jaxen.util.AncestorOrSelfAxisIterator;
  import org.jaxen.util.DescendantAxisIterator;
  import org.jaxen.util.DescendantOrSelfAxisIterator;
  import org.jaxen.util.FollowingAxisIterator;
  import org.jaxen.util.FollowingSiblingAxisIterator;
  import org.jaxen.util.PrecedingAxisIterator;
  import org.jaxen.util.PrecedingSiblingAxisIterator;
  import org.jaxen.util.SelfAxisIterator;
  
  /** Default implementation of {@link Navigator}.
   *
   *  <p>
   *  This implementation is an abstract class, since
   *  some required operations cannot be implemented without
   *  additional knowledge of the object model.
   *  </p>
   *
   *  <p>
   *  When possible, default method implementations build
   *  upon each other, to reduce the number of methods required
   *  to be implemented for each object model.  All methods,
   *  of course, may be overridden, to provide more-efficient
   *  implementations.
   *  </p>
   *
   *  @author bob mcwhirter (bob@werken.com)
   *  @author Erwin Bolwidt (ejb@klomp.org)
   */
  public abstract class DefaultNavigator implements Navigator
  {
  
      /** Throws <code>UnsupportedAxisException</code>
       * 
       * @param contextNode
       * @return never returns
       * @throws UnsupportedAxisException always
       */
      public Iterator getChildAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          throw new UnsupportedAxisException("child");
      }
  
      /* (non-Javadoc)
       * @see org.jaxen.Navigator#getDescendantAxisIterator(java.lang.Object)
       */
      public Iterator getDescendantAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new DescendantAxisIterator( contextNode,
                                             this );
      }
  
      /** Throws <code>UnsupportedAxisException</code>
       * 
       * @param  contextNode
       * @return never returns
       * @throws UnsupportedAxisException
       */
      public Iterator getParentAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          throw new UnsupportedAxisException("parent");
      }
  
      public Iterator getAncestorAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new AncestorAxisIterator( contextNode,
                                           this );
      }
  
  
      public Iterator getFollowingSiblingAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new FollowingSiblingAxisIterator( contextNode,
                                                   this );
      }
  
  
      public Iterator getPrecedingSiblingAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new PrecedingSiblingAxisIterator( contextNode,
                                                   this );
      }
  
      public Iterator getFollowingAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new FollowingAxisIterator( contextNode,
                                            this );
  
          // throw new UnsupportedAxisException("following");
      }
  
  
      public Iterator getPrecedingAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new PrecedingAxisIterator( contextNode,
                                           this );
  
          // throw new UnsupportedAxisException("preceding");
      }
  
      /** Throws <code>UnsupportedAxisException</code>. Subclasses that 
       * support the attribute axis must override this method.
       * 
       * @param contextNode
       * @return never returns
       * @throws UnsupportedAxisException
       */
      public Iterator getAttributeAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          throw new UnsupportedAxisException("attribute");
      }
  
      /** Throws <code>UnsupportedAxisException</code>. Subclasses that 
       * support the namespace axis must override this method.
       * 
       * @param contextNode
       * @return never returns
       * @throws UnsupportedAxisException
       */
      public Iterator getNamespaceAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          throw new UnsupportedAxisException("namespace");
      }
  
      public Iterator getSelfAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new SelfAxisIterator( contextNode );
      }
  
      public Iterator getDescendantOrSelfAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new DescendantOrSelfAxisIterator( contextNode,
                                                   this );
      }
  
      public Iterator getAncestorOrSelfAxisIterator(Object contextNode) throws UnsupportedAxisException
      {
          return new AncestorOrSelfAxisIterator( contextNode,
                                                 this );
      }
  
      public Object getDocumentNode(Object contextNode)
      {
          return null;
      }
      
      public String translateNamespacePrefixToUri(String prefix, Object element)
      {
          return null;
      }
  
      public String getProcessingInstructionTarget(Object obj)
      {
          return null;
      }
  
      public String getProcessingInstructionData(Object obj)
      {
          return null;
      }
  
      public short getNodeType(Object node)
      {
          if ( isElement(node) ) 
          {
              return Pattern.ELEMENT_NODE;
          }
          else if ( isAttribute(node) ) 
          {
              return Pattern.ATTRIBUTE_NODE;
          }
          else if ( isText(node) ) 
          {
              return Pattern.TEXT_NODE;
          }
          else if ( isComment(node) ) 
          {
              return Pattern.COMMENT_NODE;
          }
          else if ( isDocument(node) ) 
          {
              return Pattern.DOCUMENT_NODE;
          }
          else if ( isProcessingInstruction(node) ) 
          {
              return Pattern.PROCESSING_INSTRUCTION_NODE;
          }
          else if ( isNamespace(node) ) 
          {
              return Pattern.NAMESPACE_NODE;
          }
          else {
              return Pattern.UNKNOWN_NODE;
          }
      }
      
      /**
       * Default inefficient implementation. Subclasses 
       * should override this method.
       *
       * @param contextNode   the node whose parent to return
       * @return the parent node
       * @throws UnsupportedAxisException if the parent axis is not supported
       */
      public Object getParentNode(Object contextNode) throws UnsupportedAxisException
      {
          Iterator iter = getParentAxisIterator( contextNode );
          if ( iter != null && iter.hasNext() )
          {
              return iter.next();
          }
          return null;
      }
  
      /**
       *  Default implementation that always returns null. Override in subclass
       *  if the subclass can load documents. 
       *
       * @param url the URL of the document to load
       *
       * @return null
       * @throws FunctionCallException if an error occurs while loading the
       *    URL; e.g. an I/O error or the document is malformed
       */
      public Object getDocument(String url) throws FunctionCallException
      {
          return null;
      }
  
      /**
       *  Default implementation that cannot find elements. Override in subclass
       *  if subclass does know about attribute types.
       *
       *  @param contextNode   a node from the document in which to look for the
       *                       id
       *  @param elementId   id to look for
       *
       *  @return   null
       */
      public Object getElementById(Object contextNode, String elementId)
      {
          return null;
      }
      
  }
  