gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/engine/ComputerTraversalEngine.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.engine;

import org.apache.tinkerpop.gremlin.process.computer.GraphComputer;
import org.apache.tinkerpop.gremlin.process.computer.traversal.step.map.ComputerResultStep;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalEngine;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.EmptyStep;
import org.apache.tinkerpop.gremlin.process.traversal.strategy.AbstractTraversalStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.strategy.finalization.ProfileStrategy;
import org.apache.tinkerpop.gremlin.structure.Graph;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;

import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public final class ComputerTraversalEngine implements TraversalEngine {

    private final transient GraphComputer graphComputer;

    private ComputerTraversalEngine(final GraphComputer graphComputer) {
        this.graphComputer = graphComputer;
    }

    @Override
    public Type getType() {
        return Type.COMPUTER;
    }

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

    @Override
    public Optional<GraphComputer> getGraphComputer() {
        return Optional.ofNullable(this.graphComputer);
    }

    public static Builder build() {
        return new Builder();
    }

    public final static class Builder implements TraversalEngine.Builder {

        private Class<? extends GraphComputer> graphComputerClass;
        private int workers = -1;
        private static final List<TraversalStrategy> WITH_STRATEGIES = Collections.singletonList(ComputerResultStrategy.instance());


        @Override
        public List<TraversalStrategy> getWithStrategies() {
            return WITH_STRATEGIES;
        }

        public Builder workers(final int workers) {
            this.workers = workers;
            return this;
        }

        public Builder computer(final Class<? extends GraphComputer> graphComputerClass) {
            this.graphComputerClass = graphComputerClass;
            return this;
        }


        public ComputerTraversalEngine create(final Graph graph) {
            final GraphComputer graphComputer = null == this.graphComputerClass ? graph.compute() : graph.compute(this.graphComputerClass);
            if (-1 != this.workers)
                graphComputer.workers(this.workers);
            return new ComputerTraversalEngine(graphComputer);
        }
    }

    ////

    public static class ComputerResultStrategy extends AbstractTraversalStrategy<TraversalStrategy.FinalizationStrategy> implements TraversalStrategy.FinalizationStrategy {

        private static final ComputerResultStrategy INSTANCE = new ComputerResultStrategy();
        private static final Set<Class<? extends FinalizationStrategy>> PRIORS = new HashSet<>();

        static {
            PRIORS.add(ProfileStrategy.class);
        }


        private ComputerResultStrategy() {

        }

        @Override
        public void apply(final Traversal.Admin<?, ?> traversal) {
            if (traversal.getParent() instanceof EmptyStep) {
                final TraversalEngine engine = traversal.getEngine();
                if (engine.isComputer())
                    traversal.addStep(new ComputerResultStep<>(traversal, engine.getGraphComputer().get(), true));
            }
        }

        @Override
        public Set<Class<? extends FinalizationStrategy>> applyPrior() {
            return PRIORS;
        }

        public static ComputerResultStrategy instance() {
            return INSTANCE;
        }
    }
}