package org.aksw.sparqlify.platform.config;

import java.util.Collections;
import java.util.List;

import org.aksw.jena_sparql_api.core.QueryExecutionFactory;

import org.apache.jena.query.QueryExecution;
import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.Property;
import org.apache.jena.rdf.model.Resource;

import de.fuberlin.wiwiss.pubby.DataSource;

/**
 * A data source backed by a QueryExecutionFactory.
 *
 * @author Claus Stadler
 */
public class QefDataSource implements DataSource {
    private String previousDescribeQuery;
    private QueryExecutionFactory qef;

    private String endpointURN;
    /*
    private String defaultGraphName;
    */

    public QefDataSource(QueryExecutionFactory qef, String endpointURN) {
        this.qef = qef;
        this.endpointURN = endpointURN;
    }

    public String getEndpointURL() {
        return endpointURN;
    }

    public String getResourceDescriptionURL(String resourceURI) {
            return "DESCRIBE <" + resourceURI + ">";
            /*
        try {
            StringBuffer result = new StringBuffer();
            result.append(endpointURL);
            result.append("?");
            if (defaultGraphName != null) {
                result.append("default-graph-uri=");
                result.append(URLEncoder.encode(defaultGraphName, "utf-8"));
                result.append("&");
            }
            result.append("query=");
            result.append(URLEncoder.encode("DESCRIBE <" + resourceURI + ">",
                    "utf-8"));
            return result.toString();
        } catch (UnsupportedEncodingException ex) {
            // can't happen, utf-8 is always supported
            throw new RuntimeException(ex);
        }
            */
    }

    public Model getResourceDescription(String resourceURI) {
        return execDescribeQuery("DESCRIBE <" + resourceURI + ">");
    }

    public Model getAnonymousPropertyValues(String resourceURI,
            Property property, boolean isInverse) {
        String query = "DESCRIBE ?x WHERE { "
                + (isInverse ? "?x <" + property.getURI() + "> <" + resourceURI
                        + "> . " : "<" + resourceURI + "> <"
                        + property.getURI() + "> ?x . ")
                + "FILTER (isBlank(?x)) }";

        Model result = execDescribeQuery(query);
        return result;
    }


    public String getPreviousDescribeQuery() {
        return previousDescribeQuery;
    }

    private Model execDescribeQuery(String query) {
        previousDescribeQuery = query;
        QueryExecution qe = qef.createQueryExecution(query);

        Model result = qe.execDescribe();

        /*
        if (defaultGraphName != null) {
            endpoint.setDefaultGraphURIs(Collections
                    .singletonList(defaultGraphName));
        }
        */
        return result;
    }

    @Override
    public List<Resource> getIndex() {
        return Collections.emptyList();
    }
}