/*

  * 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.apache.commons.feedparser.locate.EntityDecoder;

 import org.jaxen.jdom.JDOMXPath;

 import org.jdom.Attribute;

 import org.jdom.CDATA;

 import org.jdom.Comment;

 import org.jdom.Element;

 import org.jdom.Text;

 import org.jdom.output.XMLOutputter;

 /**

  * http://www.intertwingly.net/wiki/pie/FrontPage

  *  

  * http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-05.txt

  * 

  * http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-04.txt

  * 

  * http://www.mnot.net/drafts/draft-nottingham-atom-format-02.html

  * 

  * http://www.ietf.org/html.charters/atompub-charter.html

  * 

  * http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-01.txt

  * 

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

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

  */

 public class AtomFeedParser extends BaseParser {

     /**

      * Parse this feed.

      *

      * 

      */

     public static void parse( FeedParserListener listener,

                               org.jdom.Document doc ) throws Exception {

         FeedParserState state = new FeedParserState( listener );

         FeedVersion v = new FeedVersion();

         v.isAtom = true;

         listener.onFeedVersion( v );

         listener.init();

         Element root = doc.getRootElement();

         doLocale( state, listener, root );

         doChannel( state, listener, doc );

         doEntry( state, listener, doc );

         doLocaleEnd( state, listener, root );

         listener.finished();

     }

     private static void doChannel( FeedParserState state,

                                    FeedParserListener listener,

                                    org.jdom.Document doc ) throws Exception {

         Element root = doc.getRootElement();

         //perform onChannel method...  (title, link, description)

         String title = selectText( "/atom:feed/atom:title", root );

         //xpath = new XPath( "/atom:feed/atom:link[atom:rel='alternate']" );

         //perform onChannel method...  (title, link, description)

         String link = selectSingleAttribute( "/atom:feed/atom:link[@rel='alternate'][@type='text/html']/@href", root );

         //String description = selectText( "/atom:feed/atom:summary[@rel='text/plain']", doc );

         String tagline = selectText( "/atom:feed/atom:tagline", root );

         //state.current = title;

         listener.onChannel( state, title, link, tagline );

         listener.onChannelEnd();

     }

     private static void doEntry( FeedParserState state,

                                  FeedParserListener listener,

                                  org.jdom.Document doc ) throws Exception {

         JDOMXPath xpath = new JDOMXPath( "/atom:feed/atom:entry" );

         xpath.setNamespaceContext( NS.context );

         List items = xpath.selectNodes( doc );

         Iterator i = items.iterator();

         //update items.

         while ( i.hasNext() ) {

             Element child = (Element)i.next();

             doLocale( state, listener, child );

             String title = selectText( "atom:title", child );

             // The "atom:link" element is a Link construct that conveys a URI

             // associated with the entry. The nature of the relationship as well

             // as the link itself is determined by the element's content.

             // atom:entry elements MUST contain at least one atom:link element

             // with a rel attribute value of "alternate".

             // atom:entry elements MUST NOT contain more than one atom:link

             // element with a rel attribute value of "alternate" that has the

             // same type attribute value.

             // atom:entry elements MAY contain additional atom:link elements

             // beyond those described above.

             String link = selectSingleAttribute( "atom:link[@rel='alternate'][@type='text/html']/@href",

                                                  child );

             // The "atom:summary" element is a Content construct that conveys a

             // short summary, abstract or excerpt of the entry. atom:entry

             // elements MAY contain an atom:created element, but MUST NOT

             // contain more than one.

             //FIXME: what if there is no type attribute specified?  Whats the default?

             // Content constructs MAY have a "type" attribute, whose value

             // indicates the media type of the content.  When present, this

             // attribute's value MUST be a media type [RFC2045].  If this

             // attribute is not present, processors MUST behave as if it were

             // present with a value of "text/ plain".

             String description = null;

             Element summary = child.getChild( "summary", NS.ATOM );

             if ( summary != null ) {

                 String type = summary.getAttributeValue( "type", NS.ATOM );

                 if ( type == null || "text/plain".equals( type ) )

                     description = summary.getText();

             }

             state.current = child;

             listener.onItem( state, title, link, description, link );

             doLink( state, listener, child );

             doMeta( state, listener, child );

             doContent( state, listener, child );

             MetaFeedParser.parse( listener, state );

             TagFeedParser.parse( listener, state );

             listener.onItemEnd();

             doLocale( state, listener, child );

         }

     }

     private static void doLink( FeedParserState state,

                                 FeedParserListener listener,

                                 Element current ) throws Exception {

         if ( listener instanceof LinkFeedParserListener == false )

             return;

         LinkFeedParserListener lfpl = (LinkFeedParserListener)listener;

         JDOMXPath xpath = new JDOMXPath( "atom:link" );

         xpath.setNamespaceContext( NS.context );

         List items = xpath.selectNodes( current );

         Iterator it = items.iterator();

         //update items.

         while ( it.hasNext() ) {

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

             String href = link.getAttributeValue( "href" );

             String rel = link.getAttributeValue( "rel" );

             String type = link.getAttributeValue( "type" );

             String title = null;

             long length = -1;

             lfpl.onLink( state, rel, type, href, title, length );

         }

     }

     private static void doContent( FeedParserState state,

                                    FeedParserListener listener,

                                    Element current ) throws Exception {

         if ( ! (listener instanceof ContentFeedParserListener) )

             return;

         ContentFeedParserListener clistener = (ContentFeedParserListener)listener;

         JDOMXPath xpath = new JDOMXPath( "atom:content" );

         xpath.setNamespaceContext( NS.context );

         List items = xpath.selectNodes( current );

         Iterator i = items.iterator();

         //update items.

         while ( i.hasNext() ) {

             Element content = (Element)i.next();

             doLocale( state, listener, content );

             String type = content.getAttributeValue( "type", "text/plain" );

             String mode = content.getAttributeValue( "mode" );

             String format = null;

             String encoding = null;

             String value = null;

             //

             if ( "xml".equals( mode ) ) {

                 value = content.getText();

             } else if ( "escaped".equals( mode ) ) {

                 //need to decode the content here &lt; -> < etc.

                 value = getXMLOfContent( content.getContent() );

                 value = EntityDecoder.decode( value );

             } else {

                 mode = "xml";

                 value = getXMLOfContent( content.getContent() );

             }

             boolean isSummary = false;

             clistener.onContent( state, type, format, encoding, mode, value, isSummary );

             doLocaleEnd( state, listener, content );

         }

         xpath = new JDOMXPath( "atom:summary[@type='application/xhtml+xml']" );

         xpath.setNamespaceContext( NS.context );

         Element e = (Element)xpath.selectSingleNode( current );

         if ( e != null ) {

             String type = "text/html";

             String format = "application/xhtml+xml";

             String encoding = null;

             String mode = "xml";

             //FIXME: get xml:base to expand the URIs.

             String value = getXMLOfContent( e );

             boolean isSummary = true;

             clistener.onContent( state, type, format, encoding, mode, value, isSummary );

         }

     }

     private static String getXMLOfContent( Element element ) {

         return getXMLOfContent( element.getContent() );

     }

     /**

      * Get the content of the given element.

      *

      * 

      */

     private static String getXMLOfContent( List content ) {

         //NOTE: Fri Mar 04 2005 03:59 PM (burton1@rojo.com): in my profiling I

         //found that this is a BIG memory allocater.  FIXME: We SHOULD be able

         //to do the same thing we do for xhtml:body RIGHT?

         StringBuffer buff = new StringBuffer( 10000 ); 

         // NOTE: Changed this constructor to use the default Format. Since the

         // constructor used no longer exists in jdom 1.0.

         XMLOutputter outputter = new XMLOutputter();

         Iterator it = content.iterator();

         while ( it.hasNext() ) {

             Object next = it.next();

             if ( next instanceof String ) {

                 buff.append( (String)next );

             } else if ( next instanceof Element ) {

                 buff.append( outputter.outputString( (Element)next ) );

             } else if ( next instanceof CDATA ) {

                 buff.append( ((CDATA)next).getText() );

             } else if ( next instanceof Comment ) {

                 buff.append( outputter.outputString( (Comment)next ) );

             } else if ( next instanceof Text ) {

                 buff.append( outputter.outputString( (Text)next ) );

             } 

         } 

         return buff.toString();

     }

     private static void doMeta( FeedParserState state,

                                 FeedParserListener listener,

                                 Element element ) throws Exception {

         //FIXME: move this code to MetaFeedParser...

         if ( ! (listener instanceof MetaFeedParserListener) ) 

             return;

         MetaFeedParserListener mlistener = (MetaFeedParserListener)listener;

         //handle issued, created, and then dublin core..

         String subject = selectText( "dc:subject", element);

         if ( subject != null ) {

             mlistener.onSubject( state, subject );

             mlistener.onSubjectEnd();

         } 

     }

     private static Element selectSingleElement( String query, org.jdom.Document doc ) throws Exception {

         JDOMXPath xpath = new JDOMXPath( query );

         xpath.setNamespaceContext( NS.context );

         //perform onChannel method...  (title, link, description)

         return (Element)xpath.selectSingleNode( doc );

     }

     private static String selectSingleAttribute( String query, Element element ) throws Exception {

         JDOMXPath xpath = new JDOMXPath( query );

         xpath.setNamespaceContext( NS.context );

         //perform onChannel method...  (title, link, description)

         Attribute a = (Attribute)xpath.selectSingleNode( element );

         if ( a == null )

             return null;

         return a.getValue();

     }

 }