package es.cbgp.galaxy.sparql.jena;

import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Iterator;

import com.hp.hpl.jena.ontology.OntModel;
import com.hp.hpl.jena.query.*;
import com.hp.hpl.jena.shared.Lock;

public class SPARQLQueryEngine {

	private OntModel queryModel;
	private String sparqlFile;

	public SPARQLQueryEngine(OntModel om) {
		this.queryModel = om;
	}

	public String executeQuery() throws Exception {
		String finalQuery = loadQueryFromFile();
		// System.out.println("Final query: " + finalQuery);
		Query query = null;
		QueryExecution qexec = null;
		try {
			queryModel.enterCriticalSection(Lock.READ);
			query = QueryFactory.create(finalQuery);
			qexec = QueryExecutionFactory.create(query, queryModel);
			ResultSet results = qexec.execSelect();
			String res = "";
			while (results.hasNext()) {
				QuerySolution qs = results.next();
				Iterator<String> vars = qs.varNames();
				while (vars.hasNext()) {
					String var = vars.next();
					if (!qs.getResource(var).isAnon()) {
						res += "?" + var + "\t" + qs.getResource(var) + "\n";
					}
				}
			}
			return res;
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			queryModel.leaveCriticalSection();
			if (qexec != null) {
				qexec.close();
			}
		}
		return null;
	}

	private String loadQueryFromFile() throws Exception {
		String query = "";
		BufferedReader bL = new BufferedReader(new FileReader(this.sparqlFile));
		while (bL.ready()) {
			query += bL.readLine();
		}
		bL.close();
		return query;
	}

	public void setQueryFile(String sparqlFile) {
		this.sparqlFile = sparqlFile;
	}
}