/*
    * Copyright (C) 2009 The Guava Authors
    *
    * Licensed 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 com.google.common.collect;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.EnumSet;
  
  /**
   * Implementation of {@link ImmutableSet} backed by a non-empty {@link
   * java.util.EnumSet}.
   *
   * @author Jared Levy
   */
  @GwtCompatible(serializable = true, emulated = true)
  @SuppressWarnings("serial") // we're overriding default serialization
  final class ImmutableEnumSet<E extends Enum<E>> extends ImmutableSet<E> {
    static <E extends Enum<E>> ImmutableSet<E> asImmutable(EnumSet<E> set) {
      switch (set.size()) {
        case 0:
          return ImmutableSet.of();
        case 1:
          return ImmutableSet.of(Iterables.getOnlyElement(set));
        default:
          return new ImmutableEnumSet<E>(set);
      }
    }
  
    /*
     * Notes on EnumSet and <E extends Enum<E>>:
     *
     * This class isn't an arbitrary ForwardingImmutableSet because we need to
     * know that calling {@code clone()} during deserialization will return an
     * object that no one else has a reference to, allowing us to guarantee
     * immutability. Hence, we support only {@link EnumSet}.
     */
    private final transient EnumSet<E> delegate;
  
    private ImmutableEnumSet(EnumSet<E> delegate) {
      this.delegate = delegate;
    }
  
    @Override boolean isPartialView() {
      return false;
    }
  
    @Override public UnmodifiableIterator<E> iterator() {
      return Iterators.unmodifiableIterator(delegate.iterator());
    }
  
    @Override
    public int size() {
      return delegate.size();
    }
  
    @Override public boolean contains(Object object) {
      return delegate.contains(object);
    }
  
    @Override public boolean containsAll(Collection<?> collection) {
      return delegate.containsAll(collection);
    }
  
    @Override public boolean isEmpty() {
      return delegate.isEmpty();
    }
  
    @Override public boolean equals(Object object) {
      return object == this || delegate.equals(object);
    }
  
    private transient int hashCode;
  
    @Override public int hashCode() {
      int result = hashCode;
      return (result == 0) ? hashCode = delegate.hashCode() : result;
    }
  
    @Override public String toString() {
      return delegate.toString();
    }
  
    // All callers of the constructor are restricted to <E extends Enum<E>>.
   @Override Object writeReplace() {
     return new EnumSerializedForm<E>(delegate);
   }
 
   /*
    * This class is used to serialize ImmutableEnumSet instances.
    */
   private static class EnumSerializedForm<E extends Enum<E>>
       implements Serializable {
     final EnumSet<E> delegate;
     EnumSerializedForm(EnumSet<E> delegate) {
       this.delegate = delegate;
     }
     Object readResolve() {
       // EJ2 #76: Write readObject() methods defensively.
       return new ImmutableEnumSet<E>(delegate.clone());
     }
     private static final long serialVersionUID = 0;
   }
 }