/*
 * 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.jena.sparql.core.describe;

import org.apache.jena.query.* ;
import org.apache.jena.rdf.model.Model ;
import org.apache.jena.rdf.model.Resource ;
import org.apache.jena.sparql.ARQConstants ;
import org.apache.jena.sparql.core.DatasetGraph;
import org.apache.jena.sparql.util.Closure ;
import org.apache.jena.sparql.util.Context ;

/**
 * DescribeHandler that calculates the bNode closure. Takes all the statements of
 * this resource, and for every object that is a bNode, it recursively includes its
 * statements.
 */

public class DescribeBNodeClosure implements DescribeHandler {
    Model acc;
    Dataset dataset;

    public DescribeBNodeClosure() {}

    @Override
    public void start(Model accumulateResultModel, Context cxt) {
        acc = accumulateResultModel;
        Object obj = cxt.get(ARQConstants.sysCurrentDataset);
        if ( obj instanceof Dataset )
            this.dataset = (Dataset)obj;
        else if ( obj instanceof DatasetGraph )
            this.dataset = DatasetFactory.wrap((DatasetGraph)obj);
    }

    // DISTINCT - we only need each ?g once.
    private static Query query = QueryFactory.create("SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } }");

    // Check all named graphs
    @Override
    public void describe(Resource r) {
        // Default model.
        Closure.closure(otherModel(r, dataset.getDefaultModel()), false, acc);

        // Find all the named graphs in which this resource
        // occurs as a subject. Faster than iterating in the
        // names of graphs in the case of very large numbers
        // of graphs, few of which contain the resource, in
        // some kind of persistent storage.

        QuerySolutionMap qsm = new QuerySolutionMap();
        qsm.add("s", r);
        try ( QueryExecution qExec = QueryExecution
                    .dataset(dataset).query(query).substitution(qsm).build() ) {
            ResultSet rs = qExec.execSelect();
            for ( ; rs.hasNext() ; ) {
                QuerySolution qs = rs.next();
                String gName = qs.getResource("g").getURI();
                Model model = dataset.getNamedModel(gName);
                Resource r2 = otherModel(r, model);
                Closure.closure(r2, false, acc);
            }
        }

//        // Named graphs
//        for ( Iterator<String> iter = dataset.listNames() ; iter.hasNext() ; )
//        {
//            String name = iter.next();
//            Model model =  dataset.getNamedModel(name) ;
//            Resource r2 = otherModel(r, model) ;
//            Closure.closure(r2, false, acc) ;
//        }

        Closure.closure(r, false, acc);
    }

    private static Resource otherModel(Resource r, Model model) {
        if ( r.isURIResource() )
            return model.createResource(r.getURI());
        if ( r.isAnon() )
            return model.createResource(r.getId());
        // Literals do not need converting.
        return r;
    }

    @Override
    public void finish() {}
}
