content: /*
   * 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 com.datastax.dse.driver.internal.core.graph;
  
  import com.datastax.dse.driver.api.core.graph.GraphNode;
  import com.datastax.oss.driver.internal.core.util.CountingIterator;
  import com.datastax.oss.driver.shaded.guava.common.base.Preconditions;
  import java.util.Queue;
  import net.jcip.annotations.NotThreadSafe;
  import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
  
  @NotThreadSafe // wraps a mutable queue
  class GraphResultIterator extends CountingIterator<GraphNode> {
  
    private final Queue<GraphNode> data;
    private final GraphProtocol graphProtocol;
  
    // Sometimes a traversal can yield the same result multiple times consecutively. To avoid
    // duplicating the data, DSE graph sends it only once with a counter indicating how many times
    // it's repeated.
    private long repeat = 0;
    private GraphNode lastGraphNode = null;
  
    GraphResultIterator(Queue<GraphNode> data, GraphProtocol graphProtocol) {
      super(data.size());
      this.data = data;
      this.graphProtocol = graphProtocol;
    }
  
    @Override
    protected GraphNode computeNext() {
      if (repeat > 1) {
        repeat -= 1;
        // Note that we don't make a defensive copy, we assume the client won't mutate the node
        return lastGraphNode;
      }
  
      GraphNode container = data.poll();
      if (container == null) {
        return endOfData();
      }
  
      if (graphProtocol.isGraphBinary()) {
        // results are contained in a Traverser object and not a Map if the protocol
        // is GraphBinary
        Preconditions.checkState(
            container.as(Object.class) instanceof Traverser,
            "Graph protocol error. Received object should be a Traverser but it is not.");
        Traverser t = container.as(Traverser.class);
        this.repeat = t.bulk();
        this.lastGraphNode = new ObjectGraphNode(t.get());
        return lastGraphNode;
      } else {
        // The repeat counter is called "bulk" in the JSON payload
        GraphNode b = container.getByKey("bulk");
        if (b != null) {
          this.repeat = b.asLong();
        }
  
        lastGraphNode = container.getByKey("result");
        return lastGraphNode;
      }
    }
  }
  