/**
    * Copyright 2008-2010 Digital Enterprise Research Institute (DERI)
    *
    * 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.deri.any23.extractor.html;
  
  import org.deri.any23.extractor.ExtractionContext;
  import org.deri.any23.extractor.ExtractionException;
  import org.deri.any23.extractor.ExtractionParameters;
  import org.deri.any23.extractor.ExtractionResult;
  import org.deri.any23.extractor.Extractor.TagSoupDOMExtractor;
  import org.deri.any23.extractor.ExtractorDescription;
  import org.deri.any23.extractor.ExtractorFactory;
  import org.deri.any23.extractor.SimpleExtractorFactory;
  import org.deri.any23.rdf.Any23ValueFactoryWrapper;
  import org.deri.any23.rdf.PopularPrefixes;
  import org.deri.any23.vocab.FOAF;
  import org.deri.any23.vocab.XFN;
  import org.openrdf.model.BNode;
  import org.openrdf.model.URI;
  import org.openrdf.model.impl.ValueFactoryImpl;
  import org.openrdf.model.vocabulary.RDF;
  import org.w3c.dom.Document;
  import org.w3c.dom.Node;
  
  import java.io.IOException;
  import java.util.Arrays;
  
  /**
   * Extractor for the <a href="http://microformats.org/wiki/xfn">XFN</a>
   * microformat.
   *
   * @author Richard Cyganiak (richard@cyganiak.de)
   */
  public class XFNExtractor implements TagSoupDOMExtractor {
  
      private static final FOAF vFOAF = FOAF.getInstance();
      private static final XFN  vXFN  = XFN.getInstance();
  
      private final static Any23ValueFactoryWrapper factoryWrapper =
              new Any23ValueFactoryWrapper(ValueFactoryImpl.getInstance());
  
      private HTMLDocument     document;
      private ExtractionResult out;
  
      public final static ExtractorFactory<XFNExtractor> factory =
              SimpleExtractorFactory.create(
                  "html-mf-xfn",
                  PopularPrefixes.createSubset("rdf", "foaf", "xfn"),
                  Arrays.asList("text/html;q=0.1", "application/xhtml+xml;q=0.1"),
                  null,
                  XFNExtractor.class
              );
  
      public ExtractorDescription getDescription() {
          return factory;
      }
  
      public void run(
              ExtractionParameters extractionParameters,
              ExtractionContext extractionContext,
              Document in,
              ExtractionResult out
      ) throws IOException, ExtractionException {
          factoryWrapper.setErrorReporter(out);
          try {
              document = new HTMLDocument(in);
              this.out = out;
  
              BNode subject = factoryWrapper.createBNode();
              boolean foundAnyXFN = false;
              final URI documentURI = extractionContext.getDocumentURI();
              for (Node link : document.findAll("//A[@rel][@href]")) {
                  foundAnyXFN |= extractLink(link, subject, documentURI);
              }
              if (!foundAnyXFN) return;
              out.writeTriple(subject, RDF.TYPE, vFOAF.Person);
              out.writeTriple(subject, vXFN.mePage, documentURI);
          } finally {
              factoryWrapper.setErrorReporter(null);
          }
      }
  
      private boolean extractLink(Node firstLink, BNode subject, URI documentURI)
      throws ExtractionException {
          String href = firstLink.getAttributes().getNamedItem("href").getNodeValue();
         String rel = firstLink.getAttributes().getNamedItem("rel").getNodeValue();
 
         String[] rels = rel.split("\\s+");
         URI link = document.resolveURI(href);
         if (containsRelMe(rels)) {
             if (containsXFNRelExceptMe(rels)) {
                 return false;    // "me" cannot be combined with any other XFN values
             }
             out.writeTriple(subject, vXFN.mePage, link);
             out.writeTriple(documentURI, vXFN.getExtendedProperty("me"), link);
         } else {
             BNode person2 = factoryWrapper.createBNode();
             boolean foundAnyXFNRel = false;
             for (String aRel : rels) {
                 foundAnyXFNRel |= extractRel(aRel, subject, documentURI, person2, link);
             }
             if (!foundAnyXFNRel) {
                 return false;
             }
             out.writeTriple(person2, RDF.TYPE, vFOAF.Person);
             out.writeTriple(person2, vXFN.mePage, link);
         }
         return true;
     }
 
     private boolean containsRelMe(String[] rels) {
         for (String rel : rels) {
             if ("me".equals(rel.toLowerCase())) {
                 return true;
             }
         }
         return false;
     }
 
     private boolean containsXFNRelExceptMe(String[] rels) {
         for (String rel : rels) {
             if (!"me".equals(rel.toLowerCase()) && vXFN.isXFNLocalName(rel)) {
                 return true;
             }
         }
         return false;
     }
 
     private boolean extractRel(String rel, BNode person1, URI uri1, BNode person2, URI uri2) {
         URI peopleProp = vXFN.getPropertyByLocalName(rel);
         URI hyperlinkProp = vXFN.getExtendedProperty(rel);
         if (peopleProp == null) {
             return false;
         }
         out.writeTriple(person1, peopleProp, person2);
         out.writeTriple(uri1, hyperlinkProp, uri2);
         return true;
     }
 
 }