gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/StartStep.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.step.sideEffect;

import org.apache.tinkerpop.gremlin.process.traversal.Step;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep;
import org.apache.tinkerpop.gremlin.structure.VertexProperty;
import org.apache.tinkerpop.gremlin.structure.util.Attachable;
import org.apache.tinkerpop.gremlin.structure.util.StringFactory;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * @author Marko A. Rodriguez (http://markorodriguez.com)
 */
public class StartStep<S> extends AbstractStep<S, S> {

    protected Object start;
    protected boolean first = true;

    public StartStep(final Traversal.Admin traversal, final Object start) {
        super(traversal);
        this.start = start;
    }

    public StartStep(final Traversal.Admin traversal) {
        this(traversal, null);
    }

    public <T> T getStart() {
        return (T) this.start;
    }

    @Override
    public String toString() {
        return StringFactory.stepString(this, this.start);
    }

    @Override
    protected Traverser.Admin<S> processNextStart() {
        if (this.first) {
            if (null != this.start) {
                if (this.start instanceof Iterator)
                    this.starts.add(this.getTraversal().getTraverserGenerator().generateIterator((Iterator<S>) this.start, this, 1l));
                else
                    this.starts.add(this.getTraversal().getTraverserGenerator().generate((S) this.start, this, 1l));
            }
            this.first = false;
        }
        ///
        final Traverser.Admin<S> start = this.starts.next();
        if (start.get() instanceof Attachable &&
                this.getTraversal().getGraph().isPresent() &&
                (!(start.get() instanceof VertexProperty) || null != ((VertexProperty) start.get()).element()))
            start.set(((Attachable<S>) start.get()).attach(Attachable.Method.get(this.getTraversal().getGraph().get())));
        return start;
    }

    @Override
    public StartStep<S> clone() {
        final StartStep<S> clone = (StartStep<S>) super.clone();
        clone.first = true;
        clone.start = null; // TODO: is this good?
        return clone;
    }

    @Override
    public int hashCode() {
        int result = super.hashCode();
        if (this.start instanceof Iterator) {
            final Iterator iterator = (Iterator) this.start;
            final List list = new ArrayList();
            while (iterator.hasNext()) {
                final Object item = iterator.next();
                if (item != null) result ^= item.hashCode();
                list.add(item);
            }
            this.start = list.iterator();
        } else if (this.start != null) {
            result ^= this.start.hashCode();
        }
        return result;
    }

    public static boolean isVariableStartStep(final Step<?, ?> step) {
        return step.getClass().equals(StartStep.class) && null == ((StartStep) step).start && ((StartStep) step).labels.size() == 1;
    }
}