gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/computer/traversal/step/map/PageRankVertexProgramStep.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.computer.traversal.step.map;

import org.apache.tinkerpop.gremlin.process.computer.GraphFilter;
import org.apache.tinkerpop.gremlin.process.computer.Memory;
import org.apache.tinkerpop.gremlin.process.computer.ranking.pagerank.PageRankVertexProgram;
import org.apache.tinkerpop.gremlin.process.computer.traversal.lambda.HaltedTraversersCountTraversal;
import org.apache.tinkerpop.gremlin.process.traversal.step.Configuring;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategies;
import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__;
import org.apache.tinkerpop.gremlin.process.traversal.step.ByModulating;
import org.apache.tinkerpop.gremlin.process.traversal.step.TimesModulating;
import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.Parameters;
import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
import org.apache.tinkerpop.gremlin.process.traversal.util.PureTraversal;
import org.apache.tinkerpop.gremlin.structure.Edge;
import org.apache.tinkerpop.gremlin.structure.Graph;
import org.apache.tinkerpop.gremlin.structure.Vertex;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;

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

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 * @author Stephen Mallette (http://stephen.genoprime.com)
 */
public final class PageRankVertexProgramStep extends VertexProgramStep
        implements TraversalParent, ByModulating, TimesModulating, Configuring {

    private Parameters parameters = new Parameters();
    private PureTraversal<Vertex, Edge> edgeTraversal;
    private String pageRankProperty = PageRankVertexProgram.PAGE_RANK;
    private int times = 20;
    private final double alpha;

    public PageRankVertexProgramStep(final Traversal.Admin traversal, final double alpha) {
        super(traversal);
        this.alpha = alpha;
        this.configure(PageRank.edges, __.<Vertex>outE().asAdmin());
    }

    @Override
    public void configure(final Object... keyValues) {
        if (keyValues[0].equals(PageRank.edges)) {
            if (!(keyValues[1] instanceof Traversal))
                throw new IllegalArgumentException("PageRank.edges requires a Traversal as its argument");
            this.edgeTraversal = new PureTraversal<>(((Traversal<Vertex,Edge>) keyValues[1]).asAdmin());
            this.integrateChild(this.edgeTraversal.get());
        } else if (keyValues[0].equals(PageRank.propertyName)) {
            if (!(keyValues[1] instanceof String))
                throw new IllegalArgumentException("PageRank.propertyName requires a String as its argument");
            this.pageRankProperty = (String) keyValues[1];
        } else if (keyValues[0].equals(PageRank.times)) {
            if (!(keyValues[1] instanceof Integer))
                throw new IllegalArgumentException("PageRank.times requires an Integer as its argument");
            this.times = (int) keyValues[1];
        }else {
            this.parameters.set(this, keyValues);
        }
    }

    @Override
    public Parameters getParameters() {
        return parameters;
    }

    /**
     * @deprecated As of release 3.4.0, replaced by {@link #configure(Object...)}
     */
    @Deprecated
    @Override
    public void modulateBy(final Traversal.Admin<?, ?> edgeTraversal) {
        configure(PageRank.edges, edgeTraversal);
    }

    /**
     * @deprecated As of release 3.4.0, replaced by {@link #configure(Object...)}
     */
    @Deprecated
    @Override
    public void modulateBy(final String pageRankProperty) {
        configure(PageRank.propertyName, pageRankProperty);
    }

    /**
     * @deprecated As of release 3.4.0, replaced by {@link #configure(Object...)}
     */
    @Deprecated
    @Override
    public void modulateTimes(int times) {
        configure(PageRank.times, times);
    }

    @Override
    public List<Traversal.Admin<Vertex, Edge>> getLocalChildren() {
        return Collections.singletonList(this.edgeTraversal.get());
    }

    @Override
    public String toString() {
        return StringFactory.stepString(this, this.edgeTraversal.get(), this.pageRankProperty, this.times, new GraphFilter(this.computer));
    }

    @Override
    public PageRankVertexProgram generateProgram(final Graph graph, final Memory memory) {
        final Traversal.Admin<Vertex, Edge> detachedTraversal = this.edgeTraversal.getPure();
        detachedTraversal.setStrategies(TraversalStrategies.GlobalCache.getStrategies(graph.getClass()));
        final PageRankVertexProgram.Builder builder = PageRankVertexProgram.build()
                .property(this.pageRankProperty)
                .iterations(this.times + 1)
                .alpha(this.alpha)
                .edges(detachedTraversal);
        if (this.previousTraversalVertexProgram())
            builder.initialRank(new HaltedTraversersCountTraversal());
        return builder.create(graph);
    }

    @Override
    public Set<TraverserRequirement> getRequirements() {
        return TraversalParent.super.getSelfAndChildRequirements();
    }

    @Override
    public PageRankVertexProgramStep clone() {
        final PageRankVertexProgramStep clone = (PageRankVertexProgramStep) super.clone();
        clone.edgeTraversal = this.edgeTraversal.clone();
        return clone;
    }

    @Override
    public void setTraversal(final Traversal.Admin<?, ?> parentTraversal) {
        super.setTraversal(parentTraversal);
        this.integrateChild(this.edgeTraversal.get());
    }

    @Override
    public int hashCode() {
        return super.hashCode() ^ this.edgeTraversal.hashCode() ^ this.pageRankProperty.hashCode() ^ this.times;
    }

}