/*
 * Copyright 2012  Research Studios Austria Forschungsges.m.b.H.
 *
 *    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 won.protocol.util.linkeddata.impl;

import org.apache.jena.query.Dataset;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.sparql.modify.UpdateProcessRemote;
import org.apache.jena.update.UpdateExecutionFactory;
import org.apache.jena.update.UpdateFactory;
import org.apache.jena.update.UpdateRequest;
import org.apache.jena.riot.Lang;
import org.apache.jena.riot.RDFDataMgr;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import won.protocol.util.linkeddata.CrawlerCallback;

import java.io.StringWriter;
import java.net.URI;
import java.util.Iterator;

/**
 * Crawler callback implementation that writes crawled data to a predefined sparql endpoint.
 */
public class SparqlUpdateCrawlerCallback implements CrawlerCallback
{
  private final Logger logger = LoggerFactory.getLogger(getClass());
  String sparqlEndpoint = null;

  public void setSparqlEndpoint(final String sparqlEndpoint) {
    this.sparqlEndpoint = sparqlEndpoint;
  }

  @Override
  public void onDatasetCrawled(final URI uri, final Dataset dataset) {

    if (null == sparqlEndpoint) {
      logger.warn("no SPARQL endpoint defined");
      return;
    }

    Iterator<String> graphNames = dataset.listNames();
    while (graphNames.hasNext()) {

      StringBuilder quadpatterns = new StringBuilder();
      String graphName = graphNames.next();
      Model model = dataset.getNamedModel(graphName);
      StringWriter sw = new StringWriter();
      RDFDataMgr.write(sw, model, Lang.NTRIPLES);
      quadpatterns.append("\nINSERT DATA { GRAPH <")
                  .append(graphName)
                  .append("> { ")
                  .append(sw)
                  .append("}};\n");

      logger.info(quadpatterns.toString());
      UpdateRequest update = UpdateFactory.create(quadpatterns.toString());
      UpdateProcessRemote riStore = (UpdateProcessRemote)
        UpdateExecutionFactory.createRemote(update, sparqlEndpoint);
      riStore.execute();

    }
  }
}