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/*
 *      Copyright (C) 2012-2016 DataStax Inc.
 *
 *      This software can be used solely with DataStax Enterprise. Please consult the license at
 *      http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
package com.datastax.dse.graph.internal;

import com.datastax.driver.dse.graph.GraphNode;
import com.datastax.driver.dse.graph.GraphResultSet;
import org.apache.tinkerpop.gremlin.process.remote.traversal.AbstractRemoteTraversal;
import org.apache.tinkerpop.gremlin.process.remote.traversal.DefaultRemoteTraverser;
import org.apache.tinkerpop.gremlin.process.remote.traversal.RemoteTraversalSideEffects;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Object returned by a {@link DseRemoteConnection} to the inner TinkerPop mechanism for
 * iterating results.
 */
class DseRemoteTraversal extends AbstractRemoteTraversal {

    private final Iterator graphNodeIterator;

    public DseRemoteTraversal(GraphResultSet graphResultSet) {
        this.graphNodeIterator = graphResultSet.iterator();
    }

    @Override
    public RemoteTraversalSideEffects getSideEffects() {
        // return null but do not throw "NotSupportedException"
        return null;
    }

    @Override
    public boolean hasNext() {
        return graphNodeIterator.hasNext();
    }

    @Override
    public E next() {
        return nextTraverser().get();
    }


    @Override
    @SuppressWarnings("unchecked")
    public Traverser.Admin nextTraverser() {
        if (hasNext()) {
            GraphNode nextGraphNode = graphNodeIterator.next();

            // get the Raw object from the ObjectGraphNode, create a new remote Traverser
            // with bulk = 1 because bulk is not supported yet. Casting should be ok
            // because we have been able to deserialize into the right type.
            return new DefaultRemoteTraverser<>((E) nextGraphNode.as(Object.class), 1);
        } else {
            // finished iterating/nothing to iterate. Normal behaviour.
            throw new NoSuchElementException();
        }
    }
}