/*

  * 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.

  */

 package org.apache.any23.extractor.html;

 import org.apache.any23.extractor.ExtractionContext;

 import org.apache.any23.extractor.ExtractionException;

 import org.apache.any23.extractor.ExtractionParameters;

 import org.apache.any23.extractor.ExtractionResult;

 import org.apache.any23.extractor.Extractor;

 import org.apache.any23.extractor.ExtractorDescription;

 import org.apache.any23.extractor.ExtractorFactory;

 import org.apache.any23.extractor.SimpleExtractorFactory;

 import org.apache.any23.rdf.PopularPrefixes;

 import org.apache.any23.rdf.RDFUtils;

 import org.apache.any23.vocab.SINDICE;

 import org.openrdf.model.URI;

 import org.openrdf.model.impl.LiteralImpl;

 import org.openrdf.model.impl.URIImpl;

 import org.w3c.dom.Document;

 import org.w3c.dom.NamedNodeMap;

 import org.w3c.dom.Node;

 import java.io.IOException;

 import java.util.Arrays;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.List;

 import java.util.Map;

 import java.util.Set;

 /**

  * This extractor represents the <i>HTML META</i> tag values

  * according the <a href="http://www.w3.org/TR/html401/struct/global.html#h-7.4.4">HTML4 specification</a>.

  *

  * @author Davide Palmisano ( dpalmisano@gmail.com )

  */

 public class HTMLMetaExtractor implements Extractor.TagSoupDOMExtractor {

     public static final String NAME = "html-head-meta";

     private static final SINDICE vSINDICE = SINDICE.getInstance();

     private URI profile;

     private Map<String, URI> prefixes = new HashMap<String, URI>();

     private String documentLang;

     /**

      * {@inheritDoc}

      */

     public final static ExtractorFactory<HTMLMetaExtractor> factory =

             SimpleExtractorFactory.create(

                     NAME,

                     PopularPrefixes.createSubset("sindice"),

                     Arrays.asList("text/html;q=0.02", "application/xhtml+xml;q=0.02"),

                     "example-meta.html",

                     HTMLMetaExtractor.class

             );

     /**

      * {@inheritDoc}

      */

     public void run(

             ExtractionParameters extractionParameters,

             ExtractionContext extractionContext,

             Document in,

             ExtractionResult out

     ) throws IOException, ExtractionException {

         profile = extractProfile(in);

         documentLang = getDocumentLanguage(in);

         extractLinkDefinedPrefixes(in);

         String baseProfile = vSINDICE.NS;

         if(profile != null) {

             baseProfile = profile.toString();

         }

         final URI documentURI = extractionContext.getDocumentURI();

         Set<Meta> metas = extractMetaElement(in, baseProfile);

         for(Meta meta : metas) {

             String lang = documentLang;

             if(meta.getLang() != null) {

                 lang = meta.getLang();

             }

             out.writeTriple(

                     documentURI,

                     meta.getName(),

                     new LiteralImpl(meta.getContent(), lang)

             );

         }

     }

     /**

      * Returns the {@link Document} language if declared, <code>null</code> otherwise.

      *

      * @param in a instance of {@link Document}.

      * @return the language declared, could be <code>null</code>.

      */

     private String getDocumentLanguage(Document in) {

         String lang = DomUtils.find(in, "string(/HTML/@lang)");

         if (lang.equals("")) {

             return null;

         }

         return lang;

     }

     private URI extractProfile(Document in) {

         String profile = DomUtils.find(in, "string(/HTML/@profile)");

         if (profile.equals("")) {

             return null;

         }

         return new URIImpl(profile);

     }

     /**

      * It extracts prefixes defined in the <i>LINK</i> meta tags.

      *

      * @param in

      */

     private void extractLinkDefinedPrefixes(Document in) {

         List<Node> linkNodes = DomUtils.findAll(in, "/HTML/HEAD/LINK");

         for(Node linkNode : linkNodes) {

             NamedNodeMap attributes = linkNode.getAttributes();

             String rel = attributes.getNamedItem("rel").getTextContent();

             String href = attributes.getNamedItem("href").getTextContent();

             if(rel != null && href !=null && RDFUtils.isAbsoluteURI(href)) {

                 prefixes.put(rel, new URIImpl(href));

             }

         }

     }

     private Set<Meta> extractMetaElement(Document in, String baseProfile) {

         List<Node> metaNodes = DomUtils.findAll(in, "/HTML/HEAD/META");

         Set<Meta> result = new HashSet<Meta>();

         for (Node metaNode : metaNodes) {

             NamedNodeMap attributes = metaNode.getAttributes();

             Node nameAttribute = attributes.getNamedItem("name");

             Node contentAttribute = attributes.getNamedItem("content");

             if (nameAttribute == null || contentAttribute == null) {

                 continue;

             }

             String name = nameAttribute.getTextContent();

             String content = contentAttribute.getTextContent();

             String xpath = DomUtils.getXPathForNode(metaNode);

             URI nameAsURI = getPrefixIfExists(name);

             if (nameAsURI == null) {

                 nameAsURI = new URIImpl(baseProfile + name);

             }

             Meta meta = new Meta(xpath, nameAsURI, content);

             result.add(meta);

         }

         return result;

     }

     private URI getPrefixIfExists(String name) {

         String[] split = name.split("\\.");

         if(split.length == 2 && prefixes.containsKey(split[0])) {

             return new URIImpl(prefixes.get(split[0]) + split[1]);

         }

         return null;

     }

     public ExtractorDescription getDescription() {

         return factory;

     }

     private class Meta {

         private String xpath;

         private URI name;

         private String lang;

         private String content;

         public Meta(String xpath, URI name, String content) {

             this.xpath = xpath;

             this.name = name;

             this.content = content;

         }

         public Meta(String xpath, URI name, String content, String lang) {

             this(xpath, name, content);

             this.lang = lang;

         }

         public URI getName() {

             return name;

         }

         public void setName(URI name) {

             this.name = name;

         }

         public String getLang() {

             return lang;

         }

         public void setLang(String lang) {

             this.lang = lang;

         }

         public String getContent() {

             return content;

         }

         public void setContent(String content) {

             this.content = content;

         }

         @Override

         public boolean equals(Object o) {

             if (this == o) return true;

             if (o == null || getClass() != o.getClass()) return false;

             Meta meta = (Meta) o;

             if (xpath != null ? !xpath.equals(meta.xpath) : meta.xpath != null) return false;

             return true;

         }

         @Override

         public int hashCode() {

             return xpath != null ? xpath.hashCode() : 0;

         }

     }

 }