/*
    * Copyright (C) 2011 The Guava Authors
    *
    * Licensed 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.google.common.cache;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Utility {@link RemovalListener} implementations intended for use in testing.
   *
   * @author mike nonemacher
   */
  @GwtCompatible(emulated = true)
  class TestingRemovalListeners {
  
    /**
     * Returns a new no-op {@code RemovalListener}.
     */
    static <K, V> NullRemovalListener<K, V> nullRemovalListener() {
      return new NullRemovalListener<K, V>();
    }
  
    /**
     * Type-inferring factory method for creating a {@link QueuingRemovalListener}.
     */
    @GwtIncompatible("ConcurrentLinkedQueue")
    static <K, V> QueuingRemovalListener<K, V> queuingRemovalListener() {
      return new QueuingRemovalListener<K,V>();
    }
  
    /**
     * Type-inferring factory method for creating a {@link CountingRemovalListener}.
     */
    static <K, V> CountingRemovalListener<K, V> countingRemovalListener() {
      return new CountingRemovalListener<K,V>();
    }
  
    /**
     * {@link RemovalListener} that adds all {@link RemovalNotification} objects to a queue.
     */
    @GwtIncompatible("ConcurrentLinkedQueue")
    static class QueuingRemovalListener<K, V>
        extends ConcurrentLinkedQueue<RemovalNotification<K, V>> implements RemovalListener<K, V> {
  
      @Override
      public void onRemoval(RemovalNotification<K, V> notification) {
        add(notification);
      }
    }
  
    /**
     * {@link RemovalListener} that counts each {@link RemovalNotification} it receives, and provides
     * access to the most-recently received one.
     */
    static class CountingRemovalListener<K, V> implements RemovalListener<K, V> {
      private final AtomicInteger count = new AtomicInteger();
      private volatile RemovalNotification<K, V> lastNotification;
  
      @Override
      public void onRemoval(RemovalNotification<K, V> notification) {
        count.incrementAndGet();
        lastNotification = notification;
      }
  
      public int getCount() {
        return count.get();
      }
  
      public K getLastEvictedKey() {
        return lastNotification.getKey();
      }
  
      public V getLastEvictedValue() {
        return lastNotification.getValue();
      }
  
      public RemovalNotification<K, V> getLastNotification() {
        return lastNotification;
      }
    }
  
    /**
     * No-op {@link RemovalListener}.
     */
   static class NullRemovalListener<K, V> implements RemovalListener<K, V> {
     @Override
     public void onRemoval(RemovalNotification<K, V> notification) {}
   }
 }