/*
 * Copyright (C) 2007 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 static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import java.util.Collection;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;

A set which forwards all its method calls to another set. Subclasses should override one or more
methods to modify the behavior of the backing set as desired per the decorator pattern.
Warning: The methods of ForwardingSet forward indiscriminately to the methods of the delegate. For example, overriding ForwardingCollection.add alone will not change the behavior of ForwardingCollection.addAll, which can lead to unexpected behavior. In this case, you should override addAll as well, either providing your own implementation, or delegating to the provided standardAddAll method. 
default method warning: This class does not forward calls to 
default methods. Instead, it inherits their default implementations. When those implementations invoke methods, they invoke methods on the ForwardingSet. 
The standard methods are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe. 
Author:
Kevin Bourrillion, Louis Wasserman
Since:
2.0/**
 * A set which forwards all its method calls to another set. Subclasses should override one or more
 * methods to modify the behavior of the backing set as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingSet} forward <b>indiscriminately</b> to the
 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #addAll}, which can lead to unexpected behavior. In this case, you should
 * override {@code addAll} as well, either providing your own implementation, or delegating to the
 * provided {@code standardAddAll} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingSet}.
 *
 * <p>The {@code standard} methods are not guaranteed to be thread-safe, even when all of the
 * methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingSet<E> extends ForwardingCollection<E> implements Set<E> {
  // TODO(lowasser): identify places where thread safety is actually lost

  
Constructor for use by subclasses. /** Constructor for use by subclasses. */
  protected ForwardingSet() {}

  @Override
  protected abstract Set<E> delegate();

  @Override
  public boolean equals(@Nullable Object object) {
    return object == this || delegate().equals(object);
  }

  @Override
  public int hashCode() {
    return delegate().hashCode();
  }

  
A sensible definition of ForwardingCollection.removeAll in terms of ForwardingCollection.iterator and ForwardingCollection.remove. If you override iterator or remove, you may wish to override ForwardingCollection.removeAll to forward to this implementation. 
Since:
7.0 (this version overrides the ForwardingCollection version as of 12.0)/**
   * A sensible definition of {@link #removeAll} in terms of {@link #iterator} and {@link #remove}.
   * If you override {@code iterator} or {@code remove}, you may wish to override {@link #removeAll}
   * to forward to this implementation.
   *
   * @since 7.0 (this version overrides the {@code ForwardingCollection} version as of 12.0)
   */
  @Override
  protected boolean standardRemoveAll(Collection<?> collection) {
    return Sets.removeAllImpl(this, checkNotNull(collection)); // for GWT
  }

  
A sensible definition of equals in terms of ForwardingCollection.size and ForwardingCollection.containsAll. If you override either of those methods, you may wish to override equals to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #equals} in terms of {@link #size} and {@link #containsAll}. If
   * you override either of those methods, you may wish to override {@link #equals} to forward to
   * this implementation.
   *
   * @since 7.0
   */
  protected boolean standardEquals(@Nullable Object object) {
    return Sets.equalsImpl(this, object);
  }

  
A sensible definition of hashCode in terms of ForwardingCollection.iterator. If you override ForwardingCollection.iterator, you may wish to override equals to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #hashCode} in terms of {@link #iterator}. If you override
   * {@link #iterator}, you may wish to override {@link #equals} to forward to this implementation.
   *
   * @since 7.0
   */
  protected int standardHashCode() {
    return Sets.hashCodeImpl(this);
  }
}