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* Licensed to the Apache Software Foundation (ASF) under one
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
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package org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration;
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.dsl.graph.__;
import org.apache.tinkerpop.gremlin.process.traversal.step.filter.AndStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.filter.ConnectiveStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.filter.OrStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.map.GraphStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.map.HasNextStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.ProfileSideEffectStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect.StartStep;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.ComputerAwareStep;
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.util.TraversalHelper;
import java.util.Set;
/**
* ConnectiveStrategy rewrites the binary conjunction form of {@code a.and().b} into a {@link AndStep} of
* {@code and(a,b)} (likewise for {@link OrStep}).
* <p/>
*
* @author Marko A. Rodriguez (http://markorodriguez.com)
* @author Daniel Kuppitz (http://gremlin.guru)
* @example <pre>
* __.has("name","stephen").or().where(__.out("knows").has("name","stephen")) // is replaced by __.or(__.has("name","stephen"), __.where(__.out("knows").has("name","stephen")))
* __.out("a").out("b").and().out("c").or().out("d") // is replaced by __.or(__.and(__.out("a").out("b"), __.out("c")), __.out("d"))
* __.as("a").out().as("b").and().as("c").in().as("d") // is replaced by __.and(__.as("a").out().as("b"), __.as("c").in().as("d"))
* </pre>
*/
public final class ConnectiveStrategy extends AbstractTraversalStrategy<TraversalStrategy.DecorationStrategy> implements TraversalStrategy.DecorationStrategy {
private static final ConnectiveStrategy INSTANCE = new ConnectiveStrategy();
private ConnectiveStrategy() {
}
@Override
public void apply(final Traversal.Admin<?, ?> traversal) {
if (TraversalHelper.hasStepOfAssignableClass(ConnectiveStep.class, traversal)) {
processConnectiveMarker(traversal);
}
}
private static boolean legalCurrentStep(final Step<?, ?> step) {
return !(step instanceof EmptyStep || step instanceof ProfileSideEffectStep || step instanceof HasNextStep ||
step instanceof ComputerAwareStep.EndStep || (step instanceof StartStep && !StartStep.isVariableStartStep(step)) ||
GraphStep.isStartStep(step));
}
private static void processConnectiveMarker(final Traversal.Admin<?, ?> traversal) {
processConjunctionMarker(OrStep.class, traversal);
processConjunctionMarker(AndStep.class, traversal);
}
private static void processConjunctionMarker(final Class<? extends ConnectiveStep> markerClass, final Traversal.Admin<?, ?> traversal) {
TraversalHelper.getStepsOfClass(markerClass, traversal).stream()
.filter(conjunctionStep -> conjunctionStep.getLocalChildren().isEmpty())
.findFirst().ifPresent(connectiveStep -> {
Step<?, ?> currentStep = connectiveStep.getNextStep();
final Traversal.Admin<?, ?> rightTraversal = __.start().asAdmin();
if (!connectiveStep.getLabels().isEmpty()) {
final StartStep<?> startStep = new StartStep<>(rightTraversal);
final Set<String> conjunctionLabels = ((Step<?, ?>) connectiveStep).getLabels();
conjunctionLabels.forEach(startStep::addLabel);
conjunctionLabels.forEach(label -> connectiveStep.removeLabel(label));
rightTraversal.addStep(startStep);
}
while (legalCurrentStep(currentStep)) {
final Step<?, ?> nextStep = currentStep.getNextStep();
rightTraversal.addStep(currentStep);
traversal.removeStep(currentStep);
currentStep = nextStep;
}
processConnectiveMarker(rightTraversal);
currentStep = connectiveStep.getPreviousStep();
final Traversal.Admin<?, ?> leftTraversal = __.start().asAdmin();
while (legalCurrentStep(currentStep)) {
final Step<?, ?> previousStep = currentStep.getPreviousStep();
leftTraversal.addStep(0, currentStep);
traversal.removeStep(currentStep);
currentStep = previousStep;
}
processConnectiveMarker(leftTraversal);
if (connectiveStep instanceof AndStep)
TraversalHelper.replaceStep((Step) connectiveStep, new AndStep(traversal, leftTraversal, rightTraversal), traversal);
else
TraversalHelper.replaceStep((Step) connectiveStep, new OrStep(traversal, leftTraversal, rightTraversal), traversal);
});
}
public static ConnectiveStrategy instance() {
return INSTANCE;
}
}