/*
    * 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.commons.collections4.bidimap;
  
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.commons.collections4.BidiMap;
  import org.apache.commons.collections4.MapIterator;
  import org.apache.commons.collections4.Unmodifiable;
  import org.apache.commons.collections4.iterators.UnmodifiableMapIterator;
  import org.apache.commons.collections4.map.UnmodifiableEntrySet;
  import org.apache.commons.collections4.set.UnmodifiableSet;
  
  /**
   * Decorates another {@link BidiMap} to ensure it can't be altered.
   * <p>
   * Attempts to modify it will result in an UnsupportedOperationException.
   * </p>
   *
   * @param <K> the type of the keys in this map
   * @param <V> the type of the values in this map
   * @since 3.0
   */
  public final class UnmodifiableBidiMap<K, V>
          extends AbstractBidiMapDecorator<K, V> implements Unmodifiable {
  
      /**
       * Factory method to create an unmodifiable map.
       * <p>
       * If the map passed in is already unmodifiable, it is returned.
       *
       * @param <K> the key type
       * @param <V> the value type
       * @param map  the map to decorate, must not be null
       * @return an unmodifiable BidiMap
       * @throws NullPointerException if map is null
       * @since 4.0
       */
      public static <K, V> BidiMap<K, V> unmodifiableBidiMap(final BidiMap<? extends K, ? extends V> map) {
          if (map instanceof Unmodifiable) {
              @SuppressWarnings("unchecked") // safe to upcast
              final BidiMap<K, V> tmpMap = (BidiMap<K, V>) map;
              return tmpMap;
          }
          return new UnmodifiableBidiMap<>(map);
      }
  
      /** The inverse unmodifiable map */
      private UnmodifiableBidiMap<V, K> inverse;
  
      /**
       * Constructor that wraps (not copies).
       *
       * @param map  the map to decorate, must not be null
       * @throws NullPointerException if map is null
       */
      @SuppressWarnings("unchecked") // safe to upcast
      private UnmodifiableBidiMap(final BidiMap<? extends K, ? extends V> map) {
          super((BidiMap<K, V>) map);
      }
  
      @Override
      public void clear() {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public Set<Map.Entry<K, V>> entrySet() {
          final Set<Map.Entry<K, V>> set = super.entrySet();
          return UnmodifiableEntrySet.unmodifiableEntrySet(set);
      }
  
      @Override
      public synchronized BidiMap<V, K> inverseBidiMap() {
          if (inverse == null) {
              inverse = new UnmodifiableBidiMap<>(decorated().inverseBidiMap());
              inverse.inverse = this;
          }
          return inverse;
      }
  
      @Override
      public Set<K> keySet() {
          final Set<K> set = super.keySet();
         return UnmodifiableSet.unmodifiableSet(set);
     }
 
     @Override
     public MapIterator<K, V> mapIterator() {
         final MapIterator<K, V> it = decorated().mapIterator();
         return UnmodifiableMapIterator.unmodifiableMapIterator(it);
     }
 
     @Override
     public V put(final K key, final V value) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void putAll(final Map<? extends K, ? extends V> mapToCopy) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public V remove(final Object key) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public K removeValue(final Object value) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Set<V> values() {
         final Set<V> set = super.values();
         return UnmodifiableSet.unmodifiableSet(set);
     }
 
 }