gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/PureTraversal.java

/*
 * 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.traversal.util;

import org.apache.commons.configuration.Configuration;
import org.apache.tinkerpop.gremlin.process.computer.util.VertexProgramHelper;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.structure.Graph;

import java.io.Serializable;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public final class PureTraversal<S, E> implements Serializable, Cloneable {

    private Traversal.Admin<S, E> pureTraversal;
    private transient Traversal.Admin<S, E> cachedTraversal;

    public PureTraversal(final Traversal.Admin<S, E> pureTraversal) {
        this.pureTraversal = pureTraversal;
    }

    public Traversal.Admin<S, E> getPure() {
        return this.pureTraversal.clone();
    }

    public Traversal.Admin<S, E> get() {
        if (null == this.cachedTraversal)
            this.cachedTraversal = this.pureTraversal.clone();
        return this.cachedTraversal;
    }

    public void storeState(final Configuration configuration, final String configurationKey) {
        try {
            VertexProgramHelper.serialize(this, configuration, configurationKey);   // the traversal can not be serialized (probably because of lambdas). As such, try direct reference.
        } catch (final IllegalArgumentException e) {
            configuration.setProperty(configurationKey, this);
        }
    }

    @Override
    public int hashCode() {
        return this.pureTraversal.hashCode();
    }

    @Override
    public boolean equals(final Object other) {
        return other instanceof PureTraversal && this.pureTraversal.equals(((PureTraversal) other).pureTraversal);
    }

    ////////////

    public static <S, E> void storeState(final Configuration configuration, final String configurationKey, final Traversal.Admin<S, E> traversal) {
        new PureTraversal<>(traversal).storeState(configuration, configurationKey);
    }

    public static <S, E> PureTraversal<S, E> loadState(final Configuration configuration, final String configurationKey, final Graph graph) {
        final Object configValue = configuration.getProperty(configurationKey);
        final PureTraversal<S, E> pureTraversal = (configValue instanceof String ? (PureTraversal<S, E>) VertexProgramHelper.deserialize(configuration, configurationKey) : ((PureTraversal<S, E>) configValue));
        pureTraversal.pureTraversal.setGraph(graph);
        return pureTraversal;
    }

    ///////////

    @Override
    public String toString() {
        return this.get().toString();
    }

    @Override
    public PureTraversal<S, E> clone() {
        try {
            final PureTraversal<S, E> clone = (PureTraversal<S, E>) super.clone();
            clone.pureTraversal = this.pureTraversal.clone();
            clone.cachedTraversal = null;
            return clone;
        } catch (final CloneNotSupportedException e) {
            throw new IllegalStateException(e.getMessage(), e);
        }
    }
}