package com.tinkerpop.gremlin.process.graph.strategy;
import com.tinkerpop.gremlin.process.Step;
import com.tinkerpop.gremlin.process.Traversal;
import com.tinkerpop.gremlin.process.TraversalStrategy;
import com.tinkerpop.gremlin.process.Traverser;
import com.tinkerpop.gremlin.process.graph.step.branch.BranchStep;
import com.tinkerpop.gremlin.process.graph.step.branch.UnionStep;
import com.tinkerpop.gremlin.process.graph.step.sideEffect.IdentityStep;
import com.tinkerpop.gremlin.process.TraversalEngine;
import com.tinkerpop.gremlin.process.util.TraversalHelper;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;
/**
* @author Marko A. Rodriguez (http://markorodriguez.com)
*/
public class UnionLinearStrategy extends AbstractTraversalStrategy {
private static final UnionLinearStrategy INSTANCE = new UnionLinearStrategy();
private static final String UNION = "gremlin.union.";
private static final String UNION_END = "gremlin.union.end.";
private UnionLinearStrategy() {
}
// x.union(a,b).y
// x.branch(t->a,t->b).a.branch(end).as(z).b.as(end).y
public void apply(final Traversal<?, ?> traversal, final TraversalEngine engine) {
if (engine.equals(TraversalEngine.STANDARD) || !TraversalHelper.hasStepOfClass(UnionStep.class, traversal))
return;
int unionStepCounter = 0;
for (final UnionStep<?, ?> unionStep : TraversalHelper.getStepsOfClass(UnionStep.class, traversal)) {
final String endLabel = UNION_END + unionStepCounter;
final List<Function<Traverser, String>> branchFunctions = new ArrayList<>();
for (int i = 0; i < unionStep.getTraversals().length; i++) {
final String unionBranchStart = UNION + unionStepCounter + "." + i;
branchFunctions.add(traverser -> unionBranchStart);
}
final BranchStep<?> branchStep = new BranchStep<>(traversal);
branchStep.setFunctions(branchFunctions.toArray(new Function[branchFunctions.size()]));
TraversalHelper.replaceStep(unionStep, branchStep, traversal);
Step currentStep = branchStep;
for (int i = 0; i < unionStep.getTraversals().length; i++) {
final String unionBranchStart = UNION + unionStepCounter + "." + i;
int c = 0;
for (final Step branchstep : unionStep.getTraversals()[i].getSteps()) {
TraversalHelper.insertAfterStep(branchstep, currentStep, traversal);
currentStep = branchstep;
if (c++ == 0) currentStep.setLabel(unionBranchStart);
}
final BranchStep breakStep = new BranchStep(traversal);
breakStep.setFunctions(new BranchStep.GoToLabel(endLabel));
TraversalHelper.insertAfterStep(breakStep, currentStep, traversal);
currentStep = breakStep;
}
final IdentityStep finalStep = new IdentityStep(traversal);
finalStep.setLabel(endLabel);
TraversalHelper.insertAfterStep(finalStep, currentStep, traversal);
unionStepCounter++;
}
}
public static UnionLinearStrategy instance() {
return INSTANCE;
}
}