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.oss.driver.internal.core.util.collection;
  
  import com.datastax.oss.driver.api.core.metadata.Node;
  import com.datastax.oss.driver.shaded.guava.common.collect.Iterators;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  import java.util.AbstractQueue;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.concurrent.atomic.AtomicInteger;
  import net.jcip.annotations.ThreadSafe;
  
  @ThreadSafe
  public abstract class QueryPlanBase extends AbstractQueue<Node> implements QueryPlan {
  
    private final AtomicInteger nextIndex = new AtomicInteger();
  
    /**
     * Returns the nodes in this query plan; the returned array should stay the same across
     * invocations.
     *
     * <p>The declared return type is {@code Object[]} because of implementation details of {@link
     * com.datastax.oss.driver.internal.core.loadbalancing.DefaultLoadBalancingPolicy
     * DefaultLoadBalancingPolicy} and {@link
     * com.datastax.oss.driver.internal.core.loadbalancing.BasicLoadBalancingPolicy
     * BasicLoadBalancingPolicy}, but all elements must be instances of {@link Node}, otherwise
     * instance methods will fail later.
     */
    protected abstract Object[] getNodes();
  
    @Nullable
    @Override
    public Node poll() {
      // We don't handle overflow. In practice it won't be an issue, since the driver stops polling
      // once the query plan is empty.
      int i = nextIndex.getAndIncrement();
      Object[] nodes = getNodes();
      return (i >= nodes.length) ? null : (Node) nodes[i];
    }
  
    @NonNull
    @Override
    public Iterator<Node> iterator() {
      int i = nextIndex.get();
      Object[] nodes = getNodes();
      if (i >= nodes.length) {
        return Collections.emptyIterator();
      } else {
        return Iterators.forArray(Arrays.copyOfRange(nodes, i, nodes.length, Node[].class));
      }
    }
  
    @Override
    public int size() {
      return Math.max(getNodes().length - nextIndex.get(), 0);
    }
  }
  