/*
    * 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.PopularPrefixes;
  import org.deri.any23.vocab.XHTML;
  import org.openrdf.model.URI;
  import org.openrdf.model.ValueFactory;
  import org.openrdf.model.impl.ValueFactoryImpl;
  import org.w3c.dom.Document;
  import org.w3c.dom.Node;
  
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.List;
  
  /**
   * This {@link org.deri.any23.extractor.Extractor.TagSoupDOMExtractor} implementation
   * retrieves the <code>LINK</code>s declared within the <code>HTML/HEAD</code> page header.
   */
  public class HeadLinkExtractor implements TagSoupDOMExtractor {
  
      public void run(
              ExtractionParameters extractionParameters,
              ExtractionContext extractionContext,
              Document in,
              ExtractionResult out
      ) throws IOException, ExtractionException {
          HTMLDocument html = new HTMLDocument(in);
          ValueFactory vf = ValueFactoryImpl.getInstance();
  
          final List<Node> headLinkNodes = DomUtils.findAll(
                  in,
                  "/HTML/HEAD/LINK[(" +
                          "@type='application/rdf+xml' or " +
                          "@type='text/rdf' or " +
                          "@type='application/x-turtle' or " +
                          "@type='application/turtle' or " +
                          "@type='text/turtle' or " +
                          "@type='text/rdf+n3'" +
                          ") and @href and @rel]"
          );
          for (Node node : headLinkNodes) {
              final URI href = html.resolveURI(DomUtils.find(node, "@href"));
              final String rel = DomUtils.find(node, "@rel");
              out.writeTriple(
                      extractionContext.getDocumentURI(),
                      vf.createURI(XHTML.NS + rel),
                      href
              );
              final String title = DomUtils.find(node, "@title");
              if (title != null && !"".equals(title)) {
                  out.writeTriple(
                          href,
                          factory.getPrefixes().expand("dcterms:title"),
                          vf.createLiteral(title)
                  );
              }
              final String type = DomUtils.find(node, "@type");
              if (type != null && !"".equals(type)) {
                  out.writeTriple(
                          href,
                          factory.getPrefixes().expand("dcterms:format"),
                          vf.createLiteral(type)
                  );
              }
          }
      }
  
      public ExtractorDescription getDescription() {
          return factory;
      }
  
      public final static ExtractorFactory<HeadLinkExtractor> factory =
              SimpleExtractorFactory.create(
                      "html-head-links",
                      PopularPrefixes.createSubset("xhtml", "dcterms"),
                     Arrays.asList("text/html;q=0.05", "application/xhtml+xml;q=0.05"),
                     null,
                     HeadLinkExtractor.class);
 }