/*
 * 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.tinkerpop.gremlin.process.computer.traversal;

import org.apache.tinkerpop.gremlin.process.computer.MessageCombiner;
import org.apache.tinkerpop.gremlin.process.traversal.traverser.util.TraverserSet;

import java.util.Optional;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public final class TraversalVertexProgramMessageCombiner implements MessageCombiner<TraverserSet<Object>> {

    private static final Optional<TraversalVertexProgramMessageCombiner> INSTANCE = Optional.of(new TraversalVertexProgramMessageCombiner());

    private TraversalVertexProgramMessageCombiner() {

    }

    public TraverserSet<Object> combine(final TraverserSet<Object> messageA, final TraverserSet<Object> messageB) {
        messageA.addAll(messageB);
        return messageA;
    }

    public static Optional<TraversalVertexProgramMessageCombiner> instance() {
        return INSTANCE;
    }
}
