/*
    * 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.multiset;
  
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.Set;
  import java.util.function.Predicate;
  
  import org.apache.commons.collections4.MultiSet;
  import org.apache.commons.collections4.Unmodifiable;
  import org.apache.commons.collections4.iterators.UnmodifiableIterator;
  import org.apache.commons.collections4.set.UnmodifiableSet;
  
  /**
   * Decorates another {@link MultiSet} to ensure it can't be altered.
   * <p>
   * Attempts to modify it will result in an UnsupportedOperationException.
   * </p>
   *
   * @param <E> the type held in the multiset
   * @since 4.1
   */
  public final class UnmodifiableMultiSet<E>
          extends AbstractMultiSetDecorator<E> implements Unmodifiable {
  
      /** Serialization version */
      private static final long serialVersionUID = 20150611L;
  
      /**
       * Factory method to create an unmodifiable multiset.
       * <p>
       * If the multiset passed in is already unmodifiable, it is returned.
       * </p>
       *
       * @param <E>  the type of the elements in the multiset
       * @param multiset  the multiset to decorate, may not be null
       * @return an unmodifiable MultiSet
       * @throws NullPointerException if multiset is null
       */
      public static <E> MultiSet<E> unmodifiableMultiSet(final MultiSet<? extends E> multiset) {
          if (multiset instanceof Unmodifiable) {
              @SuppressWarnings("unchecked") // safe to upcast
              final MultiSet<E> tmpMultiSet = (MultiSet<E>) multiset;
              return tmpMultiSet;
          }
          return new UnmodifiableMultiSet<>(multiset);
      }
  
      /**
       * Constructor that wraps (not copies).
       *
       * @param multiset  the multiset to decorate, may not be null
       * @throws NullPointerException if multiset is null
       */
      @SuppressWarnings("unchecked") // safe to upcast
      private UnmodifiableMultiSet(final MultiSet<? extends E> multiset) {
          super((MultiSet<E>) multiset);
      }
  
      @Override
      public boolean add(final E object) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public int add(final E object, final int count) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean addAll(final Collection<? extends E> coll) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public void clear() {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public Set<MultiSet.Entry<E>> entrySet() {
         final Set<MultiSet.Entry<E>> set = decorated().entrySet();
         return UnmodifiableSet.unmodifiableSet(set);
     }
 
     @Override
     public Iterator<E> iterator() {
         return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
     }
 
     /**
      * Deserializes the collection 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 cannot be loaded
      * @throws ClassCastException if deserialized object has wrong type
      */
     @SuppressWarnings("unchecked") // will throw CCE, see Javadoc
     private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
         in.defaultReadObject();
         setCollection((Collection<E>) in.readObject());
     }
 
     @Override
     public boolean remove(final Object object) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int remove(final Object object, final int count) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean removeAll(final Collection<?> coll) {
         throw new UnsupportedOperationException();
     }
 
     /**
      * @since 4.4
      */
     @Override
     public boolean removeIf(final Predicate<? super E> filter) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean retainAll(final Collection<?> coll) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int setCount(final E object, final int count) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public Set<E> uniqueSet() {
         final Set<E> set = decorated().uniqueSet();
         return UnmodifiableSet.unmodifiableSet(set);
     }
 
     /**
      * Serializes this object to an ObjectOutputStream.
      *
      * @param out the target ObjectOutputStream.
      * @throws IOException thrown when an I/O errors occur writing to the target stream.
      */
     private void writeObject(final ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
         out.writeObject(decorated());
     }
 
 }