/*

  * 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.writer;

 import org.apache.any23.extractor.ExtractionContext;

 import org.apache.any23.rdf.RDFUtils;

 import org.openrdf.model.Resource;

 import org.openrdf.model.URI;

 import org.openrdf.model.Value;

 import org.openrdf.rio.RDFHandlerException;

 import org.openrdf.rio.RDFWriter;

 /**

  * A {@link TripleHandler} that writes

  * triples to a Sesame {@link org.openrdf.rio.RDFWriter},

  * eg for serialization using one of Sesame's writers.

  *

  * @author Richard Cyganiak (richard@cyganiak.de)

  * @author Michele Mostarda (mostarda@fbk.eu)

  */

 public abstract class RDFWriterTripleHandler implements FormatWriter, TripleHandler {

     private final RDFWriter writer;

     private boolean closed = false;

     /**

      * The annotation flag.

      */

     private boolean annotated = false;

     RDFWriterTripleHandler(RDFWriter destination) {

         writer = destination;

         try {

             writer.startRDF();

         } catch (RDFHandlerException e) {

             throw new RuntimeException(e);

         }

     }

     /**

      * If <code>true</code> then the produced <b>RDF</b> is annotated with

      * the extractors used to generate the specific statements.

      *

      * @return the annotation flag value.

      */

     @Override

     public boolean isAnnotated() {

         return annotated;

     }

     /**

      * Sets the <i>annotation</i> flag.

      *

      * @param f If <code>true</code> then the produced <b>RDF</b> is annotated with

      *          the extractors used to generate the specific statements.

      */

     @Override

     public void setAnnotated(boolean f) {

         annotated = f;

     }

     @Override

     public void startDocument(URI documentURI) throws TripleHandlerException {

         // Empty.

     }

     @Override

     public void openContext(ExtractionContext context) throws TripleHandlerException {

         handleComment( String.format("BEGIN: " + context) );

     }

     @Override

     public void receiveTriple(Resource s, URI p, Value o, URI g, ExtractionContext context)

     throws TripleHandlerException {

         final URI graph = g == null ? context.getDocumentURI() : g;

         try {

             writer.handleStatement(

                     RDFUtils.quad(s, p, o, graph));

         } catch (RDFHandlerException ex) {

             throw new TripleHandlerException(

                     String.format("Error while receiving triple: %s %s %s %s", s, p, o, graph),

                     ex

             );

         }

     }

     @Override

     public void receiveNamespace(String prefix, String uri, ExtractionContext context)

     throws TripleHandlerException {

         try {

             writer.handleNamespace(prefix, uri);

         } catch (RDFHandlerException ex) {

             throw new TripleHandlerException(String.format("Error while receiving namespace: %s:%s", prefix, uri),

                     ex

             );

         }

     }

     @Override

     public void closeContext(ExtractionContext context) throws TripleHandlerException {

         handleComment( String.format("END: " + context) );

     }

     @Override

     public void close() throws TripleHandlerException {

         if (closed) return;

         closed = true;

         try {

             writer.endRDF();

         } catch (RDFHandlerException e) {

             throw new TripleHandlerException("Error while closing the triple handler.", e);

         }

     }

     @Override

     public void endDocument(URI documentURI) throws TripleHandlerException {

         // Empty.

     }

     @Override

     public void setContentLength(long contentLength) {

         // Empty.

     }

     private void handleComment(String comment) throws TripleHandlerException {

         if( !annotated ) return;

         try {

             writer.handleComment(comment);

         } catch (RDFHandlerException rdfhe) {

             throw new TripleHandlerException("Error while handing comment.", rdfhe);

         }

     }

 }