/*
    * 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.map;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.commons.collections4.IterableMap;
  import org.apache.commons.collections4.MapIterator;
  import org.apache.commons.collections4.Unmodifiable;
  import org.apache.commons.collections4.collection.UnmodifiableCollection;
  import org.apache.commons.collections4.iterators.EntrySetMapIterator;
  import org.apache.commons.collections4.iterators.UnmodifiableMapIterator;
  import org.apache.commons.collections4.set.UnmodifiableSet;
  
  /**
   * Decorates another {@code Map} to ensure it can't be altered.
   * <p>
   * This class is Serializable from Commons Collections 3.1.
   * </p>
   * <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 UnmodifiableMap<K, V>
          extends AbstractMapDecorator<K, V>
          implements Unmodifiable, Serializable {
  
      /** Serialization version */
      private static final long serialVersionUID = 2737023427269031941L;
  
      /**
       * Factory method to create an unmodifiable map.
       *
       * @param <K>  the key type
       * @param <V>  the value type
       * @param map  the map to decorate, must not be null
       * @return a new unmodifiable map
       * @throws NullPointerException if map is null
       * @since 4.0
       */
      public static <K, V> Map<K, V> unmodifiableMap(final Map<? extends K, ? extends V> map) {
          if (map instanceof Unmodifiable) {
              @SuppressWarnings("unchecked") // safe to upcast
              final Map<K, V> tmpMap = (Map<K, V>) map;
              return tmpMap;
          }
          return new UnmodifiableMap<>(map);
      }
  
      /**
       * 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 UnmodifiableMap(final Map<? extends K, ? extends V> map) {
          super((Map<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 Set<K> keySet() {
          final Set<K> set = super.keySet();
          return UnmodifiableSet.unmodifiableSet(set);
     }
 
     @Override
     public MapIterator<K, V> mapIterator() {
         if (map instanceof IterableMap) {
             final MapIterator<K, V> it = ((IterableMap<K, V>) map).mapIterator();
             return UnmodifiableMapIterator.unmodifiableMapIterator(it);
         }
         final MapIterator<K, V> it = new EntrySetMapIterator<>(map);
         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();
     }
 
     /**
      * Read the map in using a custom routine.
      *
      * @param in  the input stream
      * @throws IOException if an error occurs while reading from the stream
      * @throws ClassNotFoundException if an object read from the stream can not be loaded
      * @since 3.1
      */
     @SuppressWarnings("unchecked")
     private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
         map = (Map<K, V>) in.readObject();
     }
 
     @Override
     public V remove(final Object key) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Collection<V> values() {
         final Collection<V> coll = super.values();
         return UnmodifiableCollection.unmodifiableCollection(coll);
     }
 
     /**
      * Write the map out using a custom routine.
      *
      * @param out  the output stream
      * @throws IOException if an error occurs while writing to the stream
      * @since 3.1
      */
     private void writeObject(final ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
         out.writeObject(map);
     }
 
 }