/*
    * 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.collect.CollectPreconditions.checkNonnegative;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.VisibleForTesting;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.List;
  
  /**
   * Implementation of {@code Multimap} that uses an {@code ArrayList} to store
   * the values for a given key. A {@link HashMap} associates each key with an
   * {@link ArrayList} of values.
   *
   * <p>When iterating through the collections supplied by this class, the
   * ordering of values for a given key agrees with the order in which the values
   * were added.
   *
   * <p>This multimap allows duplicate key-value pairs. After adding a new
   * key-value pair equal to an existing key-value pair, the {@code
   * ArrayListMultimap} will contain entries for both the new value and the old
   * value.
   *
   * <p>Keys and values may be null. All optional multimap methods are supported,
   * and all returned views are modifiable.
   *
   * <p>The lists returned by {@link #get}, {@link #removeAll}, and {@link
   * #replaceValues} all implement {@link java.util.RandomAccess}.
   *
   * <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#synchronizedListMultimap}.
   * 
   * <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
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible(serializable = true, emulated = true)
  public final class ArrayListMultimap<K, V> extends AbstractListMultimap<K, V> {
    // Default from ArrayList
    private static final int DEFAULT_VALUES_PER_KEY = 3;
  
    @VisibleForTesting transient int expectedValuesPerKey;
  
    /**
     * Creates a new, empty {@code ArrayListMultimap} with the default initial
     * capacities.
     */
    public static <K, V> ArrayListMultimap<K, V> create() {
      return new ArrayListMultimap<K, V>();
    }
  
    /**
     * Constructs an empty {@code ArrayListMultimap} with enough capacity to hold
     * the specified numbers of keys and values without resizing.
     *
     * @param expectedKeys the expected number of distinct keys
     * @param expectedValuesPerKey the expected average number of values per key
     * @throws IllegalArgumentException if {@code expectedKeys} or {@code
     *      expectedValuesPerKey} is negative
     */
    public static <K, V> ArrayListMultimap<K, V> create(
        int expectedKeys, int expectedValuesPerKey) {
      return new ArrayListMultimap<K, V>(expectedKeys, expectedValuesPerKey);
    }
  
    /**
     * Constructs an {@code ArrayListMultimap} with the same mappings as the
     * specified multimap.
     *
     * @param multimap the multimap whose contents are copied to this multimap
     */
    public static <K, V> ArrayListMultimap<K, V> create(
        Multimap<? extends K, ? extends V> multimap) {
      return new ArrayListMultimap<K, V>(multimap);
    }
 
   private ArrayListMultimap() {
     super(new HashMap<K, Collection<V>>());
     expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
   }
 
   private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) {
     super(Maps.<K, Collection<V>>newHashMapWithExpectedSize(expectedKeys));
     checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
     this.expectedValuesPerKey = expectedValuesPerKey;
   }
 
   private ArrayListMultimap(Multimap<? extends K, ? extends V> multimap) {
     this(multimap.keySet().size(),
         (multimap instanceof ArrayListMultimap) ?
             ((ArrayListMultimap<?, ?>) multimap).expectedValuesPerKey :
             DEFAULT_VALUES_PER_KEY);
     putAll(multimap);
   }
 
   /**
    * Creates a new, empty {@code ArrayList} to hold the collection of values for
    * an arbitrary key.
    */
   @Override List<V> createCollection() {
     return new ArrayList<V>(expectedValuesPerKey);
   }
 
   /**
    * Reduces the memory used by this {@code ArrayListMultimap}, if feasible.
    */
   public void trimToSize() {
     for (Collection<V> collection : backingMap().values()) {
       ArrayList<V> arrayList = (ArrayList<V>) collection;
       arrayList.trimToSize();
     }
   }
 }