/*
    * Copyright (C) 2007 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.collect;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.EnumMap;
  import java.util.Map;
  
  import javax.annotation.Nullable;
  
  /**
   * A {@code BiMap} backed by an {@code EnumMap} instance for keys-to-values, and
   * a {@code HashMap} instance for values-to-keys. Null keys are not permitted,
   * but null values are. An {@code EnumHashBiMap} and its inverse are both
   * serializable.
   * 
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#BiMap">
   * {@code BiMap}</a>.
   *
   * @author Mike Bostock
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible(emulated = true)
  public final class EnumHashBiMap<K extends Enum<K>, V>
      extends AbstractBiMap<K, V> {
    private transient Class<K> keyType;
  
    /**
     * Returns a new, empty {@code EnumHashBiMap} using the specified key type.
     *
     * @param keyType the key type
     */
    public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
        create(Class<K> keyType) {
      return new EnumHashBiMap<K, V>(keyType);
    }
  
    /**
     * Constructs a new bimap with the same mappings as the specified map. If the
     * specified map is an {@code EnumHashBiMap} or an {@link EnumBiMap}, the new
     * bimap has the same key type as the input bimap. Otherwise, the specified
     * map must contain at least one mapping, in order to determine the key type.
     *
     * @param map the map whose mappings are to be placed in this map
     * @throws IllegalArgumentException if map is not an {@code EnumBiMap} or an
     *     {@code EnumHashBiMap} instance and contains no mappings
     */
    public static <K extends Enum<K>, V> EnumHashBiMap<K, V>
        create(Map<K, ? extends V> map) {
      EnumHashBiMap<K, V> bimap = create(EnumBiMap.inferKeyType(map));
      bimap.putAll(map);
      return bimap;
    }
  
    private EnumHashBiMap(Class<K> keyType) {
      super(WellBehavedMap.wrap(
          new EnumMap<K, V>(keyType)),
          Maps.<V, K>newHashMapWithExpectedSize(
              keyType.getEnumConstants().length));
      this.keyType = keyType;
    }
  
    // Overriding these 3 methods to show that values may be null (but not keys)
  
    @Override
    K checkKey(K key) {
      return checkNotNull(key);
    }
  
    @Override public V put(K key, @Nullable V value) {
      return super.put(key, value);
    }
  
    @Override public V forcePut(K key, @Nullable V value) {
      return super.forcePut(key, value);
    }
  
    /** Returns the associated key type. */
    public Class<K> keyType() {
      return keyType;
    }
 }