/*
 * 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 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;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;

/**
 * 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 net.lax1dude.eaglercraft.v1_8.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();
		}
	}

	/**
	 * @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();
		stream.writeInt(expectedValuesPerKey);
		Serialization.writeMultimap(this, stream);
	}

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

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