gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/strategy/verification/StandardVerificationStrategy.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.strategy.verification;

import org.apache.tinkerpop.gremlin.process.computer.traversal.step.VertexComputing;
import org.apache.tinkerpop.gremlin.process.computer.traversal.strategy.finalization.ComputerFinalizationStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.Step;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.step.ReadWriting;
import org.apache.tinkerpop.gremlin.process.traversal.step.branch.RepeatStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.filter.NoneStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.ProfileSideEffectStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.SideEffectCapStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.RequirementsStep;
import org.apache.tinkerpop.gremlin.process.traversal.strategy.AbstractTraversalStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalHelper;
import org.apache.tinkerpop.gremlin.structure.Graph;

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

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 * @author Stephen Mallette (http://stephen.genoprime.com)
 */
public final class StandardVerificationStrategy extends AbstractTraversalStrategy<TraversalStrategy.VerificationStrategy> implements TraversalStrategy.VerificationStrategy {

    private static final StandardVerificationStrategy INSTANCE = new StandardVerificationStrategy();

    private StandardVerificationStrategy() {
    }

    @Override
    public void apply(final Traversal.Admin<?, ?> traversal) {
        if (!traversal.getStrategies().toList().contains(ComputerFinalizationStrategy.instance()) &&
                !traversal.getStrategies().toList().contains(ComputerVerificationStrategy.instance())) {
            if (!TraversalHelper.getStepsOfAssignableClass(VertexComputing.class, traversal).isEmpty())
                throw new VerificationException("VertexComputing steps must be executed with a GraphComputer: " + TraversalHelper.getStepsOfAssignableClass(VertexComputing.class, traversal), traversal);
        }

        for (final Step<?, ?> step : traversal.getSteps()) {
            for (String label : new HashSet<>(step.getLabels())) {
                if (Graph.Hidden.isHidden(label))
                    step.removeLabel(label);
            }
            if (step instanceof ReducingBarrierStep && step.getTraversal().getParent() instanceof RepeatStep && step.getTraversal().getParent().getGlobalChildren().get(0).getSteps().contains(step))
                throw new VerificationException("The parent of a reducing barrier can not be repeat()-step: " + step, traversal);
        }

        // The ProfileSideEffectStep must be one of the following
        // (1) the last step
        // (2) 2nd last step when accompanied by the cap step or none step (i.e. iterate() to nothing)
        // (3) 3rd to last when the traversal ends with a RequirementsStep.
        final Step<?, ?> endStep = traversal.asAdmin().getEndStep();
        if (TraversalHelper.hasStepOfClass(ProfileSideEffectStep.class, traversal) &&
                !(endStep instanceof ProfileSideEffectStep ||
                        (endStep instanceof SideEffectCapStep && endStep.getPreviousStep() instanceof ProfileSideEffectStep) ||
                        (endStep instanceof NoneStep && endStep.getPreviousStep() instanceof SideEffectCapStep && endStep.getPreviousStep().getPreviousStep() instanceof ProfileSideEffectStep) ||
                        (endStep instanceof RequirementsStep && endStep.getPreviousStep() instanceof SideEffectCapStep && endStep.getPreviousStep().getPreviousStep() instanceof ProfileSideEffectStep) ||
                        (endStep instanceof RequirementsStep && endStep.getPreviousStep() instanceof NoneStep && endStep.getPreviousStep().getPreviousStep() instanceof SideEffectCapStep && endStep.getPreviousStep().getPreviousStep().getPreviousStep() instanceof ProfileSideEffectStep))) {
            throw new VerificationException("When specified, the profile()-Step must be the last step or followed only by the cap()-step.", traversal);
        }

        if (TraversalHelper.getStepsOfClass(ProfileSideEffectStep.class, traversal).size() > 1) {
            throw new VerificationException("The profile()-Step cannot be specified multiple times.", traversal);
        }
    }

    public static StandardVerificationStrategy instance() {
        return INSTANCE;
    }

    @Override
    public Set<Class<? extends VerificationStrategy>> applyPrior() {
        return Collections.singleton(ComputerVerificationStrategy.class);
    }
}