/*
    * 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.lang.reflect.Array;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Set;
  import java.util.function.Predicate;
  
  import org.apache.commons.collections4.Unmodifiable;
  import org.apache.commons.collections4.iterators.AbstractIteratorDecorator;
  import org.apache.commons.collections4.keyvalue.AbstractMapEntryDecorator;
  import org.apache.commons.collections4.set.AbstractSetDecorator;
  
  /**
   * Decorates a map entry {@code Set} 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 the map
   * @param <V> the type of the values in the map
   *
   * @since 3.0
   */
  public final class UnmodifiableEntrySet<K, V>
          extends AbstractSetDecorator<Map.Entry<K, V>> implements Unmodifiable {
  
      /**
       * Implementation of a map entry that is unmodifiable.
       */
      private final class UnmodifiableEntry extends AbstractMapEntryDecorator<K, V> {
  
          protected UnmodifiableEntry(final Map.Entry<K, V> entry) {
              super(entry);
          }
  
          @Override
          public V setValue(final V obj) {
              throw new UnsupportedOperationException();
          }
      }
  
      /**
       * Implementation of an entry set iterator.
       */
      private final class UnmodifiableEntrySetIterator extends AbstractIteratorDecorator<Map.Entry<K, V>> {
  
          protected UnmodifiableEntrySetIterator(final Iterator<Map.Entry<K, V>> iterator) {
              super(iterator);
          }
  
          @Override
          public Map.Entry<K, V> next() {
              return new UnmodifiableEntry(getIterator().next());
          }
  
          @Override
          public void remove() {
              throw new UnsupportedOperationException();
          }
      }
  
      /** Serialization version */
      private static final long serialVersionUID = 1678353579659253473L;
  
      /**
       * Factory method to create an unmodifiable set of Map Entry objects.
       *
       * @param <K>  the key type
       * @param <V>  the value type
       * @param set  the set to decorate, must not be null
       * @return a new unmodifiable entry set
       * @throws NullPointerException if set is null
       * @since 4.0
       */
      public static <K, V> Set<Map.Entry<K, V>> unmodifiableEntrySet(final Set<Map.Entry<K, V>> set) {
          if (set instanceof Unmodifiable) {
              return set;
          }
          return new UnmodifiableEntrySet<>(set);
      }
  
     /**
      * Constructor that wraps (not copies).
      *
      * @param set  the set to decorate, must not be null
      * @throws NullPointerException if set is null
      */
     private UnmodifiableEntrySet(final Set<Map.Entry<K, V>> set) {
         super(set);
     }
 
     @Override
     public boolean add(final Map.Entry<K, V> object) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean addAll(final Collection<? extends Map.Entry<K, V>> coll) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public void clear() {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Iterator<Map.Entry<K, V>> iterator() {
         return new UnmodifiableEntrySetIterator(decorated().iterator());
     }
 
     @Override
     public boolean remove(final Object object) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean removeAll(final Collection<?> coll) {
         throw new UnsupportedOperationException();
     }
 
     /**
      * @since 4.4
      */
     @Override
     public boolean removeIf(final Predicate<? super Map.Entry<K, V>> filter) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean retainAll(final Collection<?> coll) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public Object[] toArray() {
         final Object[] array = decorated().toArray();
         for (int i = 0; i < array.length; i++) {
             array[i] = new UnmodifiableEntry((Map.Entry<K, V>) array[i]);
         }
         return array;
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public <T> T[] toArray(final T[] array) {
         Object[] result = array;
         if (array.length > 0) {
             // we must create a new array to handle multithreaded situations
             // where another thread could access data before we decorate it
             result = (Object[]) Array.newInstance(array.getClass().getComponentType(), 0);
         }
         result = decorated().toArray(result);
         for (int i = 0; i < result.length; i++) {
             result[i] = new UnmodifiableEntry((Map.Entry<K, V>) result[i]);
         }
 
         // check to see if result should be returned straight
         if (result.length > array.length) {
             return (T[]) result;
         }
 
         // copy back into input array to fulfill the method contract
         System.arraycopy(result, 0, array, 0, result.length);
         if (array.length > result.length) {
             array[result.length] = null;
         }
         return array;
     }
 
 }