/*
 * 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
 *
 *   https://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.
 *
 *   SPDX-License-Identifier: Apache-2.0
 */

package org.apache.jena.riot.writer.c14n;

import java.util.Iterator;
import java.util.LinkedHashSet;

import org.apache.jena.atlas.iterator.Iter;
import org.apache.jena.graph.Graph;
import org.apache.jena.graph.TransactionHandler;
import org.apache.jena.graph.Triple;
import org.apache.jena.graph.impl.GraphBase;
import org.apache.jena.sparql.core.Match;
import org.apache.jena.sparql.graph.TransactionHandlerNull;
import org.apache.jena.util.iterator.ExtendedIterator;
import org.apache.jena.util.iterator.WrappedIterator;

/**
 * A simple graph implementation that preserves the order of triples.
 * {@link Graph#find()} will return in insertion order.
 */
public class GraphOrdered extends GraphBase {

    private LinkedHashSet<Triple> triples = new LinkedHashSet<>();
    // Secondary indexes?

    @Override
    public void performAdd(Triple t) {
        triples.add(t);
    }

    @Override
    public void performDelete(Triple t) {
        triples.remove(t);
    }

    @Override
    public TransactionHandler getTransactionHandler() {
        return new TransactionHandlerNull();
    }

    @Override
    public ExtendedIterator<Triple> find() {
        return WrappedIterator.create(triples.iterator());
    }

    @Override
    protected ExtendedIterator<Triple> graphBaseFind(Triple triplePattern) {
        Iterator<Triple> iterator = Iter.filter(triples.iterator(), triple->matches(triple, triplePattern));
        return WrappedIterator.create(iterator);
    }

    private static boolean matches(Triple tripleData, Triple triplePattern) {
        return Match.match(tripleData,
                           triplePattern.getSubject(),
                           triplePattern.getPredicate(),
                           triplePattern.getObject());
    }
}
