/*
    * 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.bag;
  
  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.Bag;
  import org.apache.commons.collections4.Unmodifiable;
  import org.apache.commons.collections4.iterators.UnmodifiableIterator;
  import org.apache.commons.collections4.set.UnmodifiableSet;
  
  /**
   * Decorates another {@link Bag} 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 <E> the type of elements in this bag
   * @since 3.0
   */
  public final class UnmodifiableBag<E>
          extends AbstractBagDecorator<E> implements Unmodifiable {
  
      /** Serialization version */
      private static final long serialVersionUID = -1873799975157099624L;
  
      /**
       * Factory method to create an unmodifiable bag.
       * <p>
       * If the bag passed in is already unmodifiable, it is returned.
       *
       * @param <E> the type of the elements in the bag
       * @param bag  the bag to decorate, must not be null
       * @return an unmodifiable Bag
       * @throws NullPointerException if bag is null
       * @since 4.0
       */
      public static <E> Bag<E> unmodifiableBag(final Bag<? extends E> bag) {
          if (bag instanceof Unmodifiable) {
              @SuppressWarnings("unchecked") // safe to upcast
              final Bag<E> tmpBag = (Bag<E>) bag;
              return tmpBag;
          }
          return new UnmodifiableBag<>(bag);
      }
  
      /**
       * Constructor that wraps (not copies).
       *
       * @param bag  the bag to decorate, must not be null
       * @throws NullPointerException if bag is null
       */
      @SuppressWarnings("unchecked") // safe to upcast
      private UnmodifiableBag(final Bag<? extends E> bag) {
          super((Bag<E>) bag);
      }
  
      @Override
      public boolean add(final E object) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean 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 Iterator<E> iterator() {
         return UnmodifiableIterator.<E>unmodifiableIterator(decorated().iterator());
     }
 
     /**
      * Read 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 can not 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 boolean 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 Set<E> uniqueSet() {
         final Set<E> set = decorated().uniqueSet();
         return UnmodifiableSet.<E>unmodifiableSet(set);
     }
 
     /**
      * Write the collection out using a custom routine.
      *
      * @param out  the output stream
      * @throws IOException if an error occurs while writing to the stream
      */
     private void writeObject(final ObjectOutputStream out) throws IOException {
         out.defaultWriteObject();
         out.writeObject(decorated());
     }
 
 }