/*

  * Copyright 1999,2004 The Apache Software Foundation.

  * 

  * Licensed 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.

  */

 package org.apache.commons.feedparser;

 import java.util.Iterator;

 import java.util.List;

 import org.jaxen.jdom.JDOMXPath;

 import org.jdom.Element;

 /**

  * Handles parsing RSS metadata including dates

  *

  * @author <a href="mailto:burton@apache.org">Kevin A. Burton (burtonator)</a>

  * @version $Id: TagFeedParser.java 373614 2006-01-30 22:31:21Z mvdb $

  */

 public class TagFeedParser {

     /**

      * 

      */

     public static void parse( FeedParserListener listener,

                               FeedParserState state ) throws Exception {

         if ( listener instanceof TagFeedParserListener == false )

             return;

         TagFeedParserListener tagFeedParserListener

             = (TagFeedParserListener)listener;

         if ( doParseModTaxonomy( tagFeedParserListener, state ) )

             return;

         if ( doParseCategory( tagFeedParserListener, state ) )

             return;

         doDcSubject( tagFeedParserListener, state );

     }

     /**

      * 

      * Parse out dc:subject tags

      *

      * Its not very clear how this is supposed to work.

      * 

      * "Comment: Typically, a Subject will be expressed as keywords, key phrases

      * or classification codes that describe a topic of the resource.

      * Recommended best practice is to select a value from a controlled

      * vocabulary or formal classification scheme."

      * 

      * But this leaves it open to whether its a space separated list or that

      * this needs to be per element.  It seems that the real infringer is

      * Delicious but I can fix this by processing dc:subject last.

      *

      * 

      */

     public static void doDcSubject( TagFeedParserListener listener, 

                                     FeedParserState state ) throws Exception {

         JDOMXPath xpath = new JDOMXPath( "dc:subject" );

         xpath.addNamespace( NS.DC.getPrefix(), NS.DC.getURI() );

         List list = xpath.selectNodes( state.current );

         Iterator it = list.iterator();

         while ( it.hasNext() ) {

             Element element = (Element)it.next();

             String tag = element.getText();

             String tagspace = null;

             listener.onTag( state, tag, tagspace );

             listener.onTagEnd();

         }

     }

     /**

      * Parse out atom:category and RSS 2.0/0.91 category

      *

      * 

      */

     public static boolean doParseCategory( TagFeedParserListener listener, 

                                            FeedParserState state ) throws Exception {

         //XPath xpath = new XPath( "local-name() = 'category'" );

         JDOMXPath xpath = new JDOMXPath( "descendant::*[local-name() = 'category']" );

         //NOTE: this only works for elements without namespaces

         //XPath xpath = new XPath( "category" );

         List list = xpath.selectNodes( state.current );

         Iterator it = list.iterator();

         boolean found = false;

         while ( it.hasNext() ) {

             Element element = (Element)it.next();

             String tag = element.getText();

             String tagspace = null;

             listener.onTag( state, tag, tagspace );

             listener.onTagEnd();

             found = true;

         }

         return found;

     }

     public static boolean doParseModTaxonomy( TagFeedParserListener listener, 

                                               FeedParserState state ) throws Exception {

         // <taxo:topics>

         //      <rdf:Bag>

         //          <rdf:li resource="http://del.icio.us/tag/hacking" />

         //          <rdf:li resource="http://del.icio.us/tag/howto" />

         //          <rdf:li resource="http://del.icio.us/tag/programming" />

         //          <rdf:li resource="http://del.icio.us/tag/software" />

         //          <rdf:li resource="http://del.icio.us/tag/tech" />

         //          <rdf:li resource="http://del.icio.us/tag/technology" />

         //          <rdf:li resource="http://del.icio.us/tag/tools" />

         //          <rdf:li resource="http://del.icio.us/tag/tivo" />

         //      </rdf:Bag>

         //  </taxo:topics>

         JDOMXPath xpath = new JDOMXPath( "taxo:topics/rdf:Bag/rdf:li" );

         xpath.addNamespace( NS.RDF.getPrefix(), NS.RDF.getURI() );

         xpath.addNamespace( NS.TAXO.getPrefix(), NS.TAXO.getURI() );

         List list = xpath.selectNodes( state.current );

         Iterator it = list.iterator();

         boolean found = false;

         while ( it.hasNext() ) {

             Element element = (Element)it.next();

             String resource = element.getAttributeValue( "resource" );

             if ( resource != "" && resource != null ) {

                 String tag = resource;

                 String tagspace = resource;

                 int begin = resource.lastIndexOf( "/" );                    

                 if ( begin != -1 ) {

                     ++begin;

                     tag = resource.substring( begin, resource.length() );

                 }

                 listener.onTag( state, tag, tagspace );

                 listener.onTagEnd();

                 found = true;

             }

         } 

         return found;

     }

 }