/*
 * 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;

import static org.apache.jena.sparql.util.graph.GraphUtils.triples2quadsDftGraph;

import java.util.Iterator;

import org.apache.jena.atlas.iterator.Iter;
import org.apache.jena.atlas.iterator.NullIterator;
import org.apache.jena.graph.Graph;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.Triple;
import org.apache.jena.query.ReadWrite ;

/**
 * DatasetGraph of a single graph as default graph. Fixed as one graph (the
 * default) - can not add named graphs.
 */
public class DatasetGraphOne extends DatasetGraphBaseFind {
    private final Graph graph;

    public DatasetGraphOne(Graph graph) {
        this.graph = graph;
    }
    
    private final Transactional txn                     = TransactionalLock.createMRSW() ;
    @Override public void begin(ReadWrite mode)         { txn.begin(mode) ; }
    @Override public void commit()                      { txn.commit() ; }
    @Override public void abort()                       { txn.abort() ; }
    @Override public boolean isInTransaction()          { return txn.isInTransaction() ; }
    @Override public void end()                         { txn.end(); }
    @Override public boolean supportsTransactions()     { return true ; }
    @Override public boolean supportsTransactionAbort() { return false ; }

    @Override
    public boolean containsGraph(Node graphNode) {
        if ( isDefaultGraph(graphNode) )
            return true;
        return false;
    }

    @Override
    public Graph getDefaultGraph() {
        return graph;
    }

    @Override
    public Graph getGraph(Node graphNode) {
        if ( isDefaultGraph(graphNode) )
            return graph;
        return null;
    }

    @Override
    public Iterator<Node> listGraphNodes() {
        return new NullIterator<>();
    }

    @Override
    public long size() {
        return 0;
    }

    @Override
    public void add(Node g, Node s, Node p, Node o) {
        if ( Quad.isDefaultGraph(g) )
            graph.add(new Triple(s, p, o));
        else
            throw new UnsupportedOperationException("DatasetGraphOne.add/named graph");
    }

    @Override
    public void add(Quad quad) {
        if ( isDefaultGraph(quad) )
            graph.add(quad.asTriple());
        else
            throw new UnsupportedOperationException("DatasetGraphOne.add/named graph");
    }

    @Override
    public void delete(Node g, Node s, Node p, Node o) {
        if ( Quad.isDefaultGraph(g) )
            graph.delete(new Triple(s, p, o));
        else
            throw new UnsupportedOperationException("DatasetGraphOne.delete/named graph");
    }

    @Override
    public void delete(Quad quad) {
        if ( isDefaultGraph(quad) )
            graph.delete(quad.asTriple());
        else
            throw new UnsupportedOperationException("DatasetGraphOne.delete/named graph");
    }

    @Override
    public void setDefaultGraph(Graph g) {
        throw new UnsupportedOperationException("DatasetGraphOne.setDefaultGraph");
    }

    @Override
    public void addGraph(Node graphName, Graph graph) {
        throw new UnsupportedOperationException("DatasetGraphOne.addGraph");
    }

    @Override
    public void removeGraph(Node graphName) {
        throw new UnsupportedOperationException("DatasetGraphOne.removeGraph");
    }

    // -- Not needed -- implement find(g,s,p,o) directly.
    @Override
    protected Iterator<Quad> findInDftGraph(Node s, Node p, Node o) {
        return triples2quadsDftGraph(graph.find(s, p, o));
    }

    @Override
    protected Iterator<Quad> findInSpecificNamedGraph(Node g, Node s, Node p, Node o) {
        // There are no named graphs
        return Iter.nullIterator();
    }

    @Override
    protected Iterator<Quad> findInAnyNamedGraphs(Node s, Node p, Node o) {
        // There are no named graphs
        return Iter.nullIterator();
    }

    protected static boolean isDefaultGraph(Quad quad) {
        return isDefaultGraph(quad.getGraph());
    }

    protected static boolean isDefaultGraph(Node quadGraphNode) {
        return (quadGraphNode == null || Quad.isDefaultGraph(quadGraphNode));
    }

    // It's just easier and more direct ...
    @Override
    public Iterator<Quad> find(Node g, Node s, Node p, Node o) {
        if ( isWildcard(g) || isDefaultGraph(g) )
            return triples2quadsDftGraph(graph.find(s, p, o));
        else
            return new NullIterator<>();
    }

    @Override
    public void close() {
        graph.close();
        super.close();
    }
}