/*
 * 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.checkArgument;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.Comparator;
import java.util.NoSuchElementException;
import java.util.SortedMap;
import org.checkerframework.checker.nullness.qual.Nullable;

A sorted map which forwards all its method calls to another sorted map. Subclasses should
override one or more methods to modify the behavior of the backing sorted map as desired per the
decorator pattern.
Warning: The methods of ForwardingSortedMap forward indiscriminately to the methods of the delegate. For example, overriding ForwardingMap.put alone will not change the behavior of ForwardingMap.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 ForwardingSortedMap. 
Each of the standard methods, where appropriate, use the comparator of the map to test equality for both keys and values, unlike ForwardingMap. 
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:
Mike Bostock, Louis Wasserman
Since:
2.0/**
 * A sorted map which forwards all its method calls to another sorted map. Subclasses should
 * override one or more methods to modify the behavior of the backing sorted 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 ForwardingSortedMap} 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 ForwardingSortedMap}.
 *
 * <p>Each of the {@code standard} methods, where appropriate, use the comparator of the map to test
 * equality for both keys and values, unlike {@code ForwardingMap}.
 *
 * <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 Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingSortedMap<K, V> extends ForwardingMap<K, V>
    implements SortedMap<K, V> {
  // TODO(lowasser): identify places where thread safety is actually lost

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

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

  @Override
  public Comparator<? super K> comparator() {
    return delegate().comparator();
  }

  @Override
  public K firstKey() {
    return delegate().firstKey();
  }

  @Override
  public SortedMap<K, V> headMap(K toKey) {
    return delegate().headMap(toKey);
  }

  @Override
  public K lastKey() {
    return delegate().lastKey();
  }

  @Override
  public SortedMap<K, V> subMap(K fromKey, K toKey) {
    return delegate().subMap(fromKey, toKey);
  }

  @Override
  public SortedMap<K, V> tailMap(K fromKey) {
    return delegate().tailMap(fromKey);
  }

  
A sensible implementation of SortedMap.keySet in terms of the methods of 
ForwardingSortedMap. In many cases, you may wish to override ForwardingMap.keySet to forward to this implementation or a subclass thereof. 
Since:
15.0/**
   * A sensible implementation of {@link SortedMap#keySet} in terms of the methods of {@code
   * ForwardingSortedMap}. In many cases, you may wish to override {@link
   * ForwardingSortedMap#keySet} to forward to this implementation or a subclass thereof.
   *
   * @since 15.0
   */
  @Beta
  protected class StandardKeySet extends Maps.SortedKeySet<K, V> {
    
Constructor for use by subclasses. /** Constructor for use by subclasses. */
    public StandardKeySet() {
      super(ForwardingSortedMap.this);
    }
  }

  // unsafe, but worst case is a CCE is thrown, which callers will be expecting
  @SuppressWarnings("unchecked")
  private int unsafeCompare(Object k1, Object k2) {
    Comparator<? super K> comparator = comparator();
    if (comparator == null) {
      return ((Comparable<Object>) k1).compareTo(k2);
    } else {
      return ((Comparator<Object>) comparator).compare(k1, k2);
    }
  }

  
A sensible definition of ForwardingMap.containsKey in terms of the firstKey() method of tailMap. If you override tailMap, you may wish to override ForwardingMap.containsKey to forward to this implementation. 
Since:
7.0/**
   * A sensible definition of {@link #containsKey} in terms of the {@code firstKey()} method of
   * {@link #tailMap}. If you override {@link #tailMap}, you may wish to override {@link
   * #containsKey} to forward to this implementation.
   *
   * @since 7.0
   */
  @Override
  @Beta
  protected boolean standardContainsKey(@Nullable Object key) {
    try {
      // any CCE will be caught
      @SuppressWarnings("unchecked")
      SortedMap<Object, V> self = (SortedMap<Object, V>) this;
      Object ceilingKey = self.tailMap(key).firstKey();
      return unsafeCompare(ceilingKey, key) == 0;
    } catch (ClassCastException | NoSuchElementException | NullPointerException e) {
      return false;
    }
  }

  
A sensible default implementation of subMap(Object, Object) in terms of headMap(Object) and tailMap(Object). In some situations, you may wish to override subMap(Object, Object) to forward to this implementation. 
Since:
7.0/**
   * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link
   * #headMap(Object)} and {@link #tailMap(Object)}. In some situations, you may wish to override
   * {@link #subMap(Object, Object)} to forward to this implementation.
   *
   * @since 7.0
   */
  @Beta
  protected SortedMap<K, V> standardSubMap(K fromKey, K toKey) {
    checkArgument(unsafeCompare(fromKey, toKey) <= 0, "fromKey must be <= toKey");
    return tailMap(fromKey).headMap(toKey);
  }
}