/*
 * 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.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

Implementation of Multimap that uses an ArrayList to store the values for a given key. A HashMap associates each key with an ArrayList of values. 
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.
This multimap allows duplicate key-value pairs. After adding a new key-value pair equal to an existing key-value pair, the ArrayListMultimap will contain entries for both the new value and the old value. 
Keys and values may be null. All optional multimap methods are supported, and all returned
views are modifiable.
The lists returned by AbstractListMultimap.get, AbstractListMultimap.removeAll, and AbstractListMultimap.replaceValues all implement RandomAccess. 
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 Multimaps.synchronizedListMultimap. 
See the Guava User Guide article on  
Multimap.
Author:
Jared Levy
Since:
2.0/**
 * 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=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap"> {@code
 * Multimap}</a>.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
public final class ArrayListMultimap<K, V>
    extends ArrayListMultimapGwtSerializationDependencies<K, V> {
  // Default from ArrayList
  private static final int DEFAULT_VALUES_PER_KEY = 3;

  @VisibleForTesting transient int expectedValuesPerKey;

  
Creates a new, empty ArrayListMultimap with the default initial capacities. 
This method will soon be deprecated in favor of 
MultimapBuilder.hashKeys().arrayListValues().build(). /**
   * Creates a new, empty {@code ArrayListMultimap} with the default initial capacities.
   *
   * <p>This method will soon be deprecated in favor of {@code
   * MultimapBuilder.hashKeys().arrayListValues().build()}.
   */
  public static <K, V> ArrayListMultimap<K, V> create() {
    return new ArrayListMultimap<>();
  }

  
Constructs an empty ArrayListMultimap with enough capacity to hold the specified numbers of keys and values without resizing. 
This method will soon be deprecated in favor of 
MultimapBuilder.hashKeys(expectedKeys).arrayListValues(expectedValuesPerKey).build(). 
Params:
expectedKeys – the expected number of distinct keys
expectedValuesPerKey – the expected average number of values per key
Throws:
IllegalArgumentException – if expectedKeys or expectedValuesPerKey is negative/**
   * Constructs an empty {@code ArrayListMultimap} with enough capacity to hold the specified
   * numbers of keys and values without resizing.
   *
   * <p>This method will soon be deprecated in favor of {@code
   * MultimapBuilder.hashKeys(expectedKeys).arrayListValues(expectedValuesPerKey).build()}.
   *
   * @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<>(expectedKeys, expectedValuesPerKey);
  }

  
Constructs an ArrayListMultimap with the same mappings as the specified multimap. 
This method will soon be deprecated in favor of 
MultimapBuilder.hashKeys().arrayListValues().build(multimap). 
Params:
multimap – the multimap whose contents are copied to this multimap/**
   * Constructs an {@code ArrayListMultimap} with the same mappings as the specified multimap.
   *
   * <p>This method will soon be deprecated in favor of {@code
   * MultimapBuilder.hashKeys().arrayListValues().build(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<>(multimap);
  }

  private ArrayListMultimap() {
    this(12, DEFAULT_VALUES_PER_KEY);
  }

  private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) {
    super(Platform.<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 ArrayList to hold the collection of values for an arbitrary key. /**
   * 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 ArrayListMultimap, if feasible. 
Deprecated:
For a ListMultimap that automatically trims to size, use ImmutableListMultimap. If you need a mutable collection, remove the trimToSize call, or switch to a HashMap<K, ArrayList<V>>./**
   * Reduces the memory used by this {@code ArrayListMultimap}, if feasible.
   *
   * @deprecated For a {@link ListMultimap} that automatically trims to size, use {@link
   *     ImmutableListMultimap}. If you need a mutable collection, remove the {@code trimToSize}
   *     call, or switch to a {@code HashMap<K, ArrayList<V>>}.
   */
  @Deprecated
  public void trimToSize() {
    for (Collection<V> collection : backingMap().values()) {
      ArrayList<V> arrayList = (ArrayList<V>) collection;
      arrayList.trimToSize();
    }
  }

  
@serialData
expectedValuesPerKey, number of distinct keys, and then for each distinct key: the
    key, number of values for that key, and the key's values/**
   * @serialData expectedValuesPerKey, number of distinct keys, and then for each distinct key: the
   *     key, number of values for that key, and the key's values
   */
  @GwtIncompatible // java.io.ObjectOutputStream
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    Serialization.writeMultimap(this, stream);
  }

  @GwtIncompatible // java.io.ObjectOutputStream
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
    int distinctKeys = Serialization.readCount(stream);
    Map<K, Collection<V>> map = Maps.newHashMap();
    setMap(map);
    Serialization.populateMultimap(this, stream, distinctKeys);
  }

  @GwtIncompatible // Not needed in emulated source.
  private static final long serialVersionUID = 0;
}