/*
* 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.step.map;
import org.apache.tinkerpop.gremlin.process.traversal.Operator;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__;
import org.apache.tinkerpop.gremlin.process.traversal.lambda.ElementValueTraversal;
import org.apache.tinkerpop.gremlin.process.traversal.lambda.FunctionTraverser;
import org.apache.tinkerpop.gremlin.process.traversal.lambda.IdentityTraversal;
import org.apache.tinkerpop.gremlin.process.traversal.lambda.TokenTraversal;
import org.apache.tinkerpop.gremlin.process.traversal.step.Barrier;
import org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating;
import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.ReducingBarrierStep;
import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalHelper;
import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;
import org.apache.tinkerpop.gremlin.util.function.HashMapSupplier;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.BinaryOperator;
/**
* @author Marko A. Rodriguez (http://markorodriguez.com)
*/
public final class GroupStep<S, K, V> extends ReducingBarrierStep<S, Map<K, V>> implements ByModulating, TraversalParent {
private char state = 'k';
private Traversal.Admin<S, K> keyTraversal;
private Traversal.Admin<S, V> valueTraversal;
private Barrier barrierStep;
public GroupStep(final Traversal.Admin traversal) {
super(traversal);
this.valueTraversal = this.integrateChild(__.fold().asAdmin());
this.barrierStep = TraversalHelper.getFirstStepOfAssignableClass(Barrier.class, this.valueTraversal).orElse(null);
this.setReducingBiOperator(new GroupBiOperator<>(null == this.barrierStep ? Operator.assign : this.barrierStep.getMemoryComputeKey().getReducer()));
this.setSeedSupplier(HashMapSupplier.instance());
}
@Override
public void modulateBy(final Traversal.Admin<?, ?> kvTraversal) {
if ('k' == this.state) {
this.keyTraversal = this.integrateChild(kvTraversal);
this.state = 'v';
} else if ('v' == this.state) {
this.valueTraversal = this.integrateChild(convertValueTraversal(kvTraversal));
this.barrierStep = TraversalHelper.getFirstStepOfAssignableClass(Barrier.class, this.valueTraversal).orElse(null);
this.setReducingBiOperator(new GroupBiOperator<>(null == this.barrierStep ? Operator.assign : this.barrierStep.getMemoryComputeKey().getReducer()));
this.state = 'x';
} else {
throw new IllegalStateException("The key and value traversals for group()-step have already been set: " + this);
}
}
@Override
public Map<K, V> projectTraverser(final Traverser.Admin<S> traverser) {
final Map<K, V> map = new HashMap<>(1);
this.valueTraversal.reset();
this.valueTraversal.addStart(traverser);
if (null == this.barrierStep) {
if (this.valueTraversal.hasNext())
map.put(TraversalUtil.applyNullable(traverser, this.keyTraversal), (V) this.valueTraversal.next());
} else if (this.barrierStep.hasNextBarrier())
map.put(TraversalUtil.applyNullable(traverser, this.keyTraversal), (V) this.barrierStep.nextBarrier());
return map;
}
@Override
public String toString() {
return StringFactory.stepString(this, this.keyTraversal, this.valueTraversal);
}
@Override
public List<Traversal.Admin<?, ?>> getLocalChildren() {
final List<Traversal.Admin<?, ?>> children = new ArrayList<>(2);
if (null != this.keyTraversal)
children.add(this.keyTraversal);
children.add(this.valueTraversal);
return children;
}
@Override
public Set<TraverserRequirement> getRequirements() {
return this.getSelfAndChildRequirements(TraverserRequirement.OBJECT, TraverserRequirement.BULK);
}
@Override
public GroupStep<S, K, V> clone() {
final GroupStep<S, K, V> clone = (GroupStep<S, K, V>) super.clone();
if (null != this.keyTraversal)
clone.keyTraversal = this.keyTraversal.clone();
clone.valueTraversal = this.valueTraversal.clone();
clone.barrierStep = TraversalHelper.getFirstStepOfAssignableClass(Barrier.class, clone.valueTraversal).orElse(null);
return clone;
}
@Override
public void setTraversal(final Traversal.Admin<?, ?> parentTraversal) {
super.setTraversal(parentTraversal);
integrateChild(this.keyTraversal);
integrateChild(this.valueTraversal);
}
@Override
public int hashCode() {
int result = super.hashCode();
if (this.keyTraversal != null) result ^= this.keyTraversal.hashCode();
result ^= this.valueTraversal.hashCode();
return result;
}
@Override
public Map<K, V> generateFinalResult(final Map<K, V> object) {
return GroupStep.doFinalReduction((Map<K, Object>) object, this.valueTraversal);
}
///////////////////////
public static final class GroupBiOperator<K, V> implements BinaryOperator<Map<K, V>>, Serializable {
private BinaryOperator<V> barrierAggregator;
public GroupBiOperator() {
// no-arg constructor for serialization
}
public GroupBiOperator(final BinaryOperator<V> barrierAggregator) {
this.barrierAggregator = barrierAggregator;
}
@Override
public Map<K, V> apply(final Map<K, V> mapA, final Map<K, V> mapB) {
for (final K key : mapB.keySet()) {
V objectA = mapA.get(key);
final V objectB = mapB.get(key);
if (null == objectA)
objectA = objectB;
else if (null != objectB)
objectA = this.barrierAggregator.apply(objectA, objectB);
mapA.put(key, objectA);
}
return mapA;
}
}
///////////////////////
public static <S, E> Traversal.Admin<S, E> convertValueTraversal(final Traversal.Admin<S, E> valueTraversal) {
if (valueTraversal instanceof ElementValueTraversal ||
valueTraversal instanceof TokenTraversal ||
valueTraversal instanceof IdentityTraversal ||
valueTraversal.getStartStep() instanceof LambdaMapStep && ((LambdaMapStep) valueTraversal.getStartStep()).getMapFunction() instanceof FunctionTraverser) {
return (Traversal.Admin<S, E>) __.map(valueTraversal).fold();
} else
return valueTraversal;
}
public static <K, V> Map<K, V> doFinalReduction(final Map<K, Object> map, final Traversal.Admin<?, V> valueTraversal) {
TraversalHelper.getFirstStepOfAssignableClass(Barrier.class, valueTraversal).ifPresent(barrierStep -> {
for (final K key : map.keySet()) {
valueTraversal.reset();
barrierStep.addBarrier(map.get(key));
if (valueTraversal.hasNext())
map.put(key, valueTraversal.next());
}
});
return (Map<K, V>) map;
}
}