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/**
 *
 * Copyright (C) 2011, NUI Galway.
 * All rights reserved.
 *
 * The software in this package is published under the terms of the BSD style license a copy of which has been included
 * with this distribution in the bsb_license.txt file and/or available on NUI Galway Server at
 * http://xsparql.deri.ie/license/bsd_license.txt
 *
 * Created: 09 February 2011, Reasoning and Querying Unit (URQ), Digital Enterprise Research Institute (DERI) on behalf of
 * NUI Galway.
 */
package org.deri.xquery.saxon;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

import javax.xml.transform.stream.StreamSource;

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.lib.ExtensionFunctionCall;
import net.sf.saxon.lib.ExtensionFunctionDefinition;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.om.StructuredQName;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.SingletonIterator;
import net.sf.saxon.value.SequenceType;

import org.deri.sparql.SPARQLQuery;

import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;

/**
 * 
 * @author Nuno Lopes
 * @version 1.0
 */
public class sparqlQueryExtFunction extends ExtensionFunctionDefinition {

  private static final long serialVersionUID = -3012293238578637469L;
  /**
   * Name of the function
   * 
   */
  private static StructuredQName funcname = new StructuredQName("_xsparql",
      "http://xsparql.deri.org/demo/xquery/xsparql.xquery", "_sparqlQuery");

  // new StructuredQName("_java", "java:org.deri.sparql.Sparql",
  // "_sparqlQuery");

  public sparqlQueryExtFunction() {
  }

  @Override
  public StructuredQName getFunctionQName() {
    return funcname;
  }

  @Override
  public int getMinimumNumberOfArguments() {
    return 1;
  }

  @Override
  public int getMaximumNumberOfArguments() {
    return 1;
  }

  @Override
  public SequenceType[] getArgumentTypes() {
    return new SequenceType[] { SequenceType.SINGLE_STRING };
  }

  @Override
  public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
    return SequenceType.ANY_SEQUENCE;
  }

  @Override
  public ExtensionFunctionCall makeCallExpression() {

    return new ExtensionFunctionCall() {

      private static final long serialVersionUID = -2933876244790032821L;

      @Override
      public SequenceIterator call(SequenceIterator[] arguments,
          XPathContext context) throws XPathException {

        String queryString = arguments[0].next().getStringValue();

        SPARQLQuery query = new SPARQLQuery(queryString);
        ResultSet resultSet = query.getResults();

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        ResultSetFormatter.outputAsXML(outputStream, resultSet);
        ByteArrayInputStream inputStream = new ByteArrayInputStream(
            outputStream.toByteArray());

        return SingletonIterator.makeIterator(context.getConfiguration()
            .buildDocument(new StreamSource(inputStream)));

      }

    };
  }

}