/*
 * 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Objects;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;

A map which forwards all its method calls to another map. Subclasses should override one or more
methods to modify the behavior of the backing map as desired per the decorator pattern.
Warning: The methods of ForwardingMap forward indiscriminately to the methods of the delegate. For example, overriding put alone will not change the behavior of putAll, which can lead to unexpected behavior. In this case, you should override putAll as well, either providing your own implementation, or delegating to the provided standardPutAll 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 ForwardingMap. 
Each of the standard methods, where appropriate, use Objects.equal to test equality for both keys and values. This may not be the desired behavior for map implementations that use non-standard notions of key equality, such as a SortedMap whose comparator is not consistent with equals. 
The standard methods and the collection views they return are not guaranteed to be thread-safe, even when all of the methods that they depend on are thread-safe. 
Author:
Kevin Bourrillion, Jared Levy, Louis Wasserman
Since:
2.0/**
 * A map which forwards all its method calls to another map. Subclasses should override one or more
 * methods to modify the behavior of the backing map as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingMap} forward <i>indiscriminately</i> to the
 * methods of the delegate. For example, overriding {@link #put} alone <i>will not</i> change the
 * behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should
 * override {@code putAll} as well, either providing your own implementation, or delegating to the
 * provided {@code standardPutAll} 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 ForwardingMap}.
 *
 * <p>Each of the {@code standard} methods, where appropriate, use {@link Objects#equal} to test
 * equality for both keys and values. This may not be the desired behavior for map implementations
 * that use non-standard notions of key equality, such as a {@code SortedMap} whose comparator is
 * not consistent with {@code equals}.
 *
 * <p>The {@code standard} methods and the collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMap<K, V> extends ForwardingObject implements Map<K, V> {
  // TODO(lowasser): identify places where thread safety is actually lost

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

  @Override
  protected abstract Map<K, V> delegate();

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

  @Override
  public boolean isEmpty() {
    return delegate().isEmpty();
  }

  @CanIgnoreReturnValue
  @Override
  public V remove(Object object) {
    return delegate().remove(object);
  }

  @Override
  public void clear() {
    delegate().clear();
  }

  @Override
  public boolean containsKey(@Nullable Object key) {
    return delegate().containsKey(key);
  }

  @Override
  public boolean containsValue(@Nullable Object value) {
    return delegate().containsValue(value);
  }

  @Override
  public V get(@Nullable Object key) {
    return delegate().get(key);
  }

  @CanIgnoreReturnValue
  @Override
  public V put(K key, V value) {
    return delegate().put(key, value);
  }

  @Override
  public void putAll(Map<? extends K, ? extends V> map) {
    delegate().putAll(map);
  }

  @Override
  public Set<K> keySet() {
    return delegate().keySet();
  }

  @Override
  public Collection<V> values() {
    return delegate().values();
  }

  @Override
  public Set<Entry<K, V>> entrySet() {
    return delegate().entrySet();
  }

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

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

  
A sensible definition of putAll(Map) in terms of put(Object, Object). If you override put(Object, Object), you may wish to override putAll(Map) to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #putAll(Map)} in terms of {@link #put(Object, Object)}. If you
   * override {@link #put(Object, Object)}, you may wish to override {@link #putAll(Map)} to forward
   * to this implementation.
   *
   * @since 7.0
   */
  protected void standardPutAll(Map<? extends K, ? extends V> map) {
    Maps.putAllImpl(this, map);
  }

  
A sensible, albeit inefficient, definition of remove in terms of the iterator method of entrySet. If you override entrySet, you may wish to override remove to forward to this implementation. 
Alternately, you may wish to override remove with keySet().remove, assuming that approach would not lead to an infinite loop. 
Since:
7.0/**
   * A sensible, albeit inefficient, definition of {@link #remove} in terms of the {@code iterator}
   * method of {@link #entrySet}. If you override {@link #entrySet}, you may wish to override {@link
   * #remove} to forward to this implementation.
   *
   * <p>Alternately, you may wish to override {@link #remove} with {@code keySet().remove}, assuming
   * that approach would not lead to an infinite loop.
   *
   * @since 7.0
   */
  @Beta
  protected V standardRemove(@Nullable Object key) {
    Iterator<Entry<K, V>> entryIterator = entrySet().iterator();
    while (entryIterator.hasNext()) {
      Entry<K, V> entry = entryIterator.next();
      if (Objects.equal(entry.getKey(), key)) {
        V value = entry.getValue();
        entryIterator.remove();
        return value;
      }
    }
    return null;
  }

  
A sensible definition of clear in terms of the iterator method of entrySet. In many cases, you may wish to override clear to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #clear} in terms of the {@code iterator} method of {@link
   * #entrySet}. In many cases, you may wish to override {@link #clear} to forward to this
   * implementation.
   *
   * @since 7.0
   */
  protected void standardClear() {
    Iterators.clear(entrySet().iterator());
  }

  
A sensible implementation of Map.keySet in terms of the following methods: ForwardingMap.clear, ForwardingMap.containsKey, ForwardingMap.isEmpty, ForwardingMap.remove, ForwardingMap.size, and the Set.iterator method of ForwardingMap.entrySet. In many cases, you may wish to override ForwardingMap.keySet to forward to this implementation or a subclass thereof. 
Since:
10.0/**
   * A sensible implementation of {@link Map#keySet} in terms of the following methods: {@link
   * ForwardingMap#clear}, {@link ForwardingMap#containsKey}, {@link ForwardingMap#isEmpty}, {@link
   * ForwardingMap#remove}, {@link ForwardingMap#size}, and the {@link Set#iterator} method of
   * {@link ForwardingMap#entrySet}. In many cases, you may wish to override {@link
   * ForwardingMap#keySet} to forward to this implementation or a subclass thereof.
   *
   * @since 10.0
   */
  @Beta
  protected class StandardKeySet extends Maps.KeySet<K, V> {
    
Constructor for use by subclasses. /** Constructor for use by subclasses. */
    public StandardKeySet() {
      super(ForwardingMap.this);
    }
  }

  
A sensible, albeit inefficient, definition of containsKey in terms of the 
iterator method of entrySet. If you override entrySet, you may wish to override containsKey to forward to this implementation. 
Since:
7.0/**
   * A sensible, albeit inefficient, definition of {@link #containsKey} in terms of the {@code
   * iterator} method of {@link #entrySet}. If you override {@link #entrySet}, you may wish to
   * override {@link #containsKey} to forward to this implementation.
   *
   * @since 7.0
   */
  @Beta
  protected boolean standardContainsKey(@Nullable Object key) {
    return Maps.containsKeyImpl(this, key);
  }

  
A sensible implementation of Map.values in terms of the following methods: ForwardingMap.clear, ForwardingMap.containsValue, ForwardingMap.isEmpty, ForwardingMap.size, and the Set.iterator method of ForwardingMap.entrySet. In many cases, you may wish to override ForwardingMap.values to forward to this implementation or a subclass thereof. 
Since:
10.0/**
   * A sensible implementation of {@link Map#values} in terms of the following methods: {@link
   * ForwardingMap#clear}, {@link ForwardingMap#containsValue}, {@link ForwardingMap#isEmpty},
   * {@link ForwardingMap#size}, and the {@link Set#iterator} method of {@link
   * ForwardingMap#entrySet}. In many cases, you may wish to override {@link ForwardingMap#values}
   * to forward to this implementation or a subclass thereof.
   *
   * @since 10.0
   */
  @Beta
  protected class StandardValues extends Maps.Values<K, V> {
    
Constructor for use by subclasses. /** Constructor for use by subclasses. */
    public StandardValues() {
      super(ForwardingMap.this);
    }
  }

  
A sensible definition of containsValue in terms of the iterator method of entrySet. If you override entrySet, you may wish to override containsValue to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #containsValue} in terms of the {@code iterator} method of
   * {@link #entrySet}. If you override {@link #entrySet}, you may wish to override {@link
   * #containsValue} to forward to this implementation.
   *
   * @since 7.0
   */
  protected boolean standardContainsValue(@Nullable Object value) {
    return Maps.containsValueImpl(this, value);
  }

  
A sensible implementation of Map.entrySet in terms of the following methods: ForwardingMap.clear, ForwardingMap.containsKey, ForwardingMap.get, ForwardingMap.isEmpty, ForwardingMap.remove, and ForwardingMap.size. In many cases, you may wish to override ForwardingMap<K,V>.entrySet to forward to this implementation or a subclass thereof. 
Since:
10.0/**
   * A sensible implementation of {@link Map#entrySet} in terms of the following methods: {@link
   * ForwardingMap#clear}, {@link ForwardingMap#containsKey}, {@link ForwardingMap#get}, {@link
   * ForwardingMap#isEmpty}, {@link ForwardingMap#remove}, and {@link ForwardingMap#size}. In many
   * cases, you may wish to override {@link #entrySet} to forward to this implementation or a
   * subclass thereof.
   *
   * @since 10.0
   */
  @Beta
  protected abstract class StandardEntrySet extends Maps.EntrySet<K, V> {
    
Constructor for use by subclasses. /** Constructor for use by subclasses. */
    public StandardEntrySet() {}

    @Override
    Map<K, V> map() {
      return ForwardingMap.this;
    }
  }

  
A sensible definition of isEmpty in terms of the iterator method of entrySet. If you override entrySet, you may wish to override isEmpty to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #isEmpty} in terms of the {@code iterator} method of {@link
   * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #isEmpty} to
   * forward to this implementation.
   *
   * @since 7.0
   */
  protected boolean standardIsEmpty() {
    return !entrySet().iterator().hasNext();
  }

  
A sensible definition of equals in terms of the equals method of entrySet. If you override entrySet, you may wish to override equals to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #equals} in terms of the {@code equals} method of {@link
   * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #equals} to
   * forward to this implementation.
   *
   * @since 7.0
   */
  protected boolean standardEquals(@Nullable Object object) {
    return Maps.equalsImpl(this, object);
  }

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

  
A sensible definition of ForwardingObject.toString in terms of the iterator method of entrySet. If you override entrySet, you may wish to override ForwardingObject.toString to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #toString} in terms of the {@code iterator} method of {@link
   * #entrySet}. If you override {@link #entrySet}, you may wish to override {@link #toString} to
   * forward to this implementation.
   *
   * @since 7.0
   */
  protected String standardToString() {
    return Maps.toStringImpl(this);
  }
}