/*
    * 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.Comparator;
  import java.util.SortedSet;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import javax.annotation.Nullable;
  
  /**
   * Implementation of {@code Multimap} whose keys and values are ordered by
   * their natural ordering or by supplied comparators. In all cases, this
   * implementation uses {@link Comparable#compareTo} or {@link
   * Comparator#compare} instead of {@link Object#equals} to determine
   * equivalence of instances.
   *
   * <p><b>Warning:</b> The comparators or comparables used must be <i>consistent
   * with equals</i> as explained by the {@link Comparable} class specification.
   * Otherwise, the resulting multiset will violate the general contract of {@link
   * SetMultimap}, which it is specified in terms of {@link Object#equals}.
   *
   * <p>The collections returned by {@code keySet} and {@code asMap} iterate
   * through the keys according to the key comparator ordering or the natural
   * ordering of the keys. Similarly, {@code get}, {@code removeAll}, and {@code
   * replaceValues} return collections that iterate through the values according
   * to the value comparator ordering or the natural ordering of the values. The
   * collections generated by {@code entries}, {@code keys}, and {@code values}
   * iterate across the keys according to the above key ordering, and for each
   * key they iterate across the values according to the value ordering.
   *
   * <p>The multimap does not store duplicate key-value pairs. Adding a new
   * key-value pair equal to an existing key-value pair has no effect.
   *
   * <p>Null keys and values are permitted (provided, of course, that the
   * respective comparators support them). All optional multimap methods are
   * supported, and all returned views are modifiable.
   *
   * <p>This class is not threadsafe when any concurrent operations update the
   * multimap. Concurrent read operations will work correctly. To allow concurrent
   * update operations, wrap your multimap with a call to {@link
   * Multimaps#synchronizedSortedSetMultimap}.
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multimap">
   * {@code Multimap}</a>.
   *
   * @author Jared Levy
   * @author Louis Wasserman
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible(serializable = true, emulated = true)
  public class TreeMultimap<K, V> extends AbstractSortedKeySortedSetMultimap<K, V> {
    private transient Comparator<? super K> keyComparator;
    private transient Comparator<? super V> valueComparator;
  
    /**
     * Creates an empty {@code TreeMultimap} ordered by the natural ordering of
     * its keys and values.
     */
    public static <K extends Comparable, V extends Comparable>
        TreeMultimap<K, V> create() {
      return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural());
    }
  
    /**
     * Creates an empty {@code TreeMultimap} instance using explicit comparators.
     * Neither comparator may be null; use {@link Ordering#natural()} to specify
     * natural order.
     *
     * @param keyComparator the comparator that determines the key ordering
     * @param valueComparator the comparator that determines the value ordering
     */
    public static <K, V> TreeMultimap<K, V> create(
        Comparator<? super K> keyComparator,
        Comparator<? super V> valueComparator) {
      return new TreeMultimap<K, V>(checkNotNull(keyComparator),
          checkNotNull(valueComparator));
    }
 
   /**
    * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its
    * keys and values, with the same mappings as the specified multimap.
    *
    * @param multimap the multimap whose contents are copied to this multimap
    */
   public static <K extends Comparable, V extends Comparable>
       TreeMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) {
     return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural(),
         multimap);
   }
 
   TreeMultimap(Comparator<? super K> keyComparator,
       Comparator<? super V> valueComparator) {
     super(new TreeMap<K, Collection<V>>(keyComparator));
     this.keyComparator = keyComparator;
     this.valueComparator = valueComparator;
   }
 
   private TreeMultimap(Comparator<? super K> keyComparator,
       Comparator<? super V> valueComparator,
       Multimap<? extends K, ? extends V> multimap) {
     this(keyComparator, valueComparator);
     putAll(multimap);
   }
 
   /**
    * {@inheritDoc}
    *
    * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
    *
    * @return a new {@code TreeSet} containing a collection of values for one
    *     key
    */
   @Override SortedSet<V> createCollection() {
     return new TreeSet<V>(valueComparator);
   }
 
   @Override
   Collection<V> createCollection(@Nullable K key) {
     if (key == null) {
       keyComparator().compare(key, key);
     }
     return super.createCollection(key);
   }
 
   /**
    * Returns the comparator that orders the multimap keys.
    */
   public Comparator<? super K> keyComparator() {
     return keyComparator;
   }
 
   @Override
   public Comparator<? super V> valueComparator() {
     return valueComparator;
   }
 
   /*
    * The following @GwtIncompatible methods override the methods in 
    * AbstractSortedKeySortedSetMultimap, so GWT will fall back to the ASKSSM implementations,
    * which return SortedSets and SortedMaps.
    */
 }