/*
 * 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 java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Comparator;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import javax.annotation.Nullable;

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

/**
 * 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.
	 */

	@Override
	@GwtIncompatible("NavigableMap")
	NavigableMap<K, Collection<V>> backingMap() {
		return (NavigableMap<K, Collection<V>>) super.backingMap();
	}

	/**
	 * @since 14.0 (present with return type {@code SortedSet} since 2.0)
	 */
	@Override
	@GwtIncompatible("NavigableSet")
	public NavigableSet<V> get(@Nullable K key) {
		return (NavigableSet<V>) super.get(key);
	}

	@Override
	@GwtIncompatible("NavigableSet")
	Collection<V> unmodifiableCollectionSubclass(Collection<V> collection) {
		return Sets.unmodifiableNavigableSet((NavigableSet<V>) collection);
	}

	@Override
	@GwtIncompatible("NavigableSet")
	Collection<V> wrapCollection(K key, Collection<V> collection) {
		return new WrappedNavigableSet(key, (NavigableSet<V>) collection, null);
	}

	/**
	 * {@inheritDoc}
	 *
	 * <p>
	 * Because a {@code TreeMultimap} has unique sorted keys, this method returns a
	 * {@link NavigableSet}, instead of the {@link java.util.Set} specified in the
	 * {@link Multimap} interface.
	 * 
	 * @since 14.0 (present with return type {@code SortedSet} since 2.0)
	 */
	@Override
	@GwtIncompatible("NavigableSet")
	public NavigableSet<K> keySet() {
		return (NavigableSet<K>) super.keySet();
	}

	@Override
	@GwtIncompatible("NavigableSet")
	NavigableSet<K> createKeySet() {
		return new NavigableKeySet(backingMap());
	}

	/**
	 * {@inheritDoc}
	 *
	 * <p>
	 * Because a {@code TreeMultimap} has unique sorted keys, this method returns a
	 * {@link NavigableMap}, instead of the {@link java.util.Map} specified in the
	 * {@link Multimap} interface.
	 * 
	 * @since 14.0 (present with return type {@code SortedMap} since 2.0)
	 */
	@Override
	@GwtIncompatible("NavigableMap")
	public NavigableMap<K, Collection<V>> asMap() {
		return (NavigableMap<K, Collection<V>>) super.asMap();
	}

	@Override
	@GwtIncompatible("NavigableMap")
	NavigableMap<K, Collection<V>> createAsMap() {
		return new NavigableAsMap(backingMap());
	}

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

	@GwtIncompatible("java.io.ObjectInputStream")
	@SuppressWarnings("unchecked") // reading data stored by writeObject
	private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
		stream.defaultReadObject();
		keyComparator = checkNotNull((Comparator<? super K>) stream.readObject());
		valueComparator = checkNotNull((Comparator<? super V>) stream.readObject());
		setMap(new TreeMap<K, Collection<V>>(keyComparator));
		Serialization.populateMultimap(this, stream);
	}

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