/*
    *
    * 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.hadoop.hbase.namequeues.queue;
  
  import com.google.common.base.Preconditions;
  import java.io.Serializable;
  import java.util.Queue;
  import java.util.concurrent.ArrayBlockingQueue;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  
  @InterfaceAudience.Private
  public final class EvictingQueue<E> implements Serializable {
  
    private final Queue<E> delegate;
    final int maxSize;
    private static final long serialVersionUID = 0L;
  
    private EvictingQueue(int maxSize) {
      Preconditions.checkArgument(maxSize >= 0, "maxSize (%s) must >= 0", maxSize);
      this.delegate = new ArrayBlockingQueue<>(maxSize);
      this.maxSize = maxSize;
    }
  
    public static <E> EvictingQueue<E> create(int maxSize) {
      return new EvictingQueue<>(maxSize);
    }
  
    public int remainingCapacity() {
      return this.maxSize - this.delegate.size();
    }
  
    protected Queue<E> delegate() {
      return this.delegate;
    }
  
    public boolean offer(E e) {
      return this.add(e);
    }
  
    public boolean add(E e) {
      Preconditions.checkNotNull(e);
      if (this.maxSize == 0) {
        return true;
      } else {
        if (this.delegate().size() == this.maxSize) {
          this.delegate.remove();
        }
        this.delegate.add(e);
        return true;
      }
    }
  
    public <T> T[] toArray(T[] array) {
      return this.delegate().toArray(array);
    }
  
    public void clear() {
      this.delegate().clear();
    }
  
    public boolean isEmpty() {
      return this.delegate().isEmpty();
    }
  
    public E poll() {
      return this.delegate().poll();
    }
  }