/*
    * 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 static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.Beta;
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.base.Objects;
  
  import java.util.Map.Entry;
  
  import javax.annotation.Nullable;
  
  /**
   * A notification of the removal of a single entry. The key and/or value may be null if they were
   * already garbage collected.
   *
   * <p>Like other {@code Map.Entry} instances associated with {@code CacheBuilder}, this class holds
   * strong references to the key and value, regardless of the type of references the cache may be
   * using.
   *
   * @author Charles Fry
   * @since 10.0
   */
  @Beta
  @GwtCompatible
  public final class RemovalNotification<K, V> implements Entry<K, V> {
    @Nullable private final K key;
    @Nullable private final V value;
    private final RemovalCause cause;
  
    RemovalNotification(@Nullable K key, @Nullable V value, RemovalCause cause) {
      this.key = key;
      this.value = value;
      this.cause = checkNotNull(cause);
    }
  
    /**
     * Returns the cause for which the entry was removed.
     */
    public RemovalCause getCause() {
      return cause;
    }
  
    /**
     * Returns {@code true} if there was an automatic removal due to eviction (the cause is neither
     * {@link RemovalCause#EXPLICIT} nor {@link RemovalCause#REPLACED}).
     */
    public boolean wasEvicted() {
      return cause.wasEvicted();
    }
  
    @Nullable @Override public K getKey() {
      return key;
    }
  
    @Nullable @Override public V getValue() {
      return value;
    }
  
    @Override public final V setValue(V value) {
      throw new UnsupportedOperationException();
    }
  
    @Override public boolean equals(@Nullable Object object) {
      if (object instanceof Entry) {
        Entry<?, ?> that = (Entry<?, ?>) object;
        return Objects.equal(this.getKey(), that.getKey())
            && Objects.equal(this.getValue(), that.getValue());
      }
      return false;
    }
  
    @Override public int hashCode() {
      K k = getKey();
      V v = getValue();
      return ((k == null) ? 0 : k.hashCode()) ^ ((v == null) ? 0 : v.hashCode());
    }
  
    /**
     * Returns a string representation of the form <code>{key}={value}</code>.
     */
    @Override public String toString() {
      return getKey() + "=" + getValue();
   }
   private static final long serialVersionUID = 0;
 }