package org.apache.maven;
   
   /* ====================================================================
    *   Licensed to the Apache Software Foundation (ASF) under one or more
    *   contributor license agreements.  See the NOTICE file distributed with
    *   this work for additional information regarding copyright ownership.
    *   The ASF licenses this file to You under the Apache License, Version 2.0
    *   (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.apache.org/licenses/LICENSE-2.0
   *
   *   Unless required by applicable law or agreed to in writing, software
   *   distributed under the License is distributed on an "AS IS" BASIS,
   *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *   See the License for the specific language governing permissions and
   *   limitations under the License.
   * ====================================================================
   */
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.xml.sax.Attributes;
  import org.xml.sax.SAXException;
  import org.xml.sax.SAXParseException;
  import org.xml.sax.helpers.XMLFilterImpl;
  
  /**
   * Constructs an XPath expression in the form:
   *    /root/child[3]/grandchild[2] ...
   *
   * @author <a href="mailto:ltheussl@apache.org">Lukas Theussl</a>
   */
  public class XPathLocationTracker extends XMLFilterImpl
  {
  
      private State state;
      private static final Integer[] ints = new Integer[]
      {
          new Integer( 0 ),
          new Integer( 1 ),
          new Integer( 2 ),
          new Integer( 3 ),
          new Integer( 4 )
      };
  
      /**
       * Overriding ContentHandler.
       * @throws SAXException SAXException
       */
      public void startDocument() throws SAXException
      {
          state = new State( null );
          super.startDocument();
      }
  
      /**
       * Overriding ContentHandler.
       * @throws SAXException SAXException
       */
      public void endDocument() throws SAXException
      {
          super.endDocument();
          state = null;
      }
  
      /**
       * Overriding ContentHandler.
       * @param uri uri
       * @param localName localName
       * @param qName qName
       * @param atts atts
       * @throws SAXException SAXException
       */
      public void startElement( String uri, String localName,
              String qName, Attributes atts ) throws SAXException
      {
          state = state.push( qName );
          try
          {
              super.startElement( uri, localName, qName, atts );
          }
          catch ( SAXParseException e )
          {
              // ignored on purpose: just avoid to throw an exception here
              // it is thrown by the ErrorHandler in JaxpMsvBean instead
          }
      }
  
      /**
       * Overriding ContentHandler.
       * @param uri uri
       * @param localName localName
       * @param qName qName
       * @throws SAXException SAXException
       */
      public void endElement( String uri, String localName, String qName )
              throws SAXException
     {
         try
         {
             super.endElement( uri, localName, qName );
         }
         catch ( SAXParseException e )
         {
             // ignored on purpose: just avoid to throw an exception here
             // it is thrown by the ErrorHandler in JaxpMsvBean instead
         }
         state = state.pop();
     }
 
     /**
      * Gets the XPath expression that points to the current location.
      * Throws a new IllegalStateException if the component is not
      * parsing a document.
      * @return The XPath expression
      */
     public final String getXPath()
     {
         if ( state == null )
         {
             throw new IllegalStateException(
                 "startDocument event is not invoked" );
         }
         return state.getXPath();
     }
 
     private static Integer getInt( int i )
     {
         if ( i < ints.length )
         {
             return ints[i];
         }
         else
         {
             return new Integer(i);
         }
     }
 
     private static final class State
     {
 
         private final Map counter = new HashMap();
         private final State parent;
         private State child;
         private String currentName;
 
         State( State newParent )
         {
             this.parent = newParent;
         }
 
         protected State push( String rawName )
         {
             count(rawName);
             currentName = rawName;
             if ( child == null )
             {
                 child = new State( this );
             }
             else
             {
                 child.reset();
             }
             return child;
         }
 
         protected State pop()
         {
             parent.currentName = null;
             return parent;
         }
 
         private void count( String rawName )
         {
             Integer i = (Integer) counter.get( rawName );
             if ( i == null )
             {
                 i = getInt( 1 );
             }
             else
             {
                 i = getInt( i.intValue() + 1 );
             }
             counter.put( rawName, i );
         }
 
         private void reset()
         {
             counter.clear();
             currentName = null;
         }
 
         private String getXPath()
         {
             String xPath;
             if ( parent == null ) // root
             {
                 xPath = "/";
                 if ( currentName != null )
                 {
                     xPath += currentName;
                 }
             }
             else // child node
             {
                 xPath = parent.getXPath();
                 if ( currentName != null )
                 {
                     xPath += '/' + currentName;
                     Integer i = (Integer) counter.get( currentName );
                     xPath += '[' + i.toString() + ']';
                 }
             }
             return xPath;
         }
 
     }
 
 }