/*
 * Copyright (C) 2008 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 java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Comparator;
import java.util.Map.Entry;

import javax.annotation.Nullable;

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

/**
 * An immutable {@link ListMultimap} with reliable user-specified key and value
 * iteration order. Does not permit null keys or values.
 *
 * <p>
 * Unlike {@link Multimaps#unmodifiableListMultimap(ListMultimap)}, which is a
 * <i>view</i> of a separate multimap which can still change, an instance of
 * {@code ImmutableListMultimap} contains its own data and will <i>never</i>
 * change. {@code ImmutableListMultimap} is convenient for
 * {@code public static final} multimaps ("constant multimaps") and also lets
 * you easily make a "defensive copy" of a multimap provided to your class by a
 * caller.
 *
 * <p>
 * <b>Note:</b> Although this class is not final, it cannot be subclassed as it
 * has no public or protected constructors. Thus, instances of this class are
 * guaranteed to be immutable.
 *
 * <p>
 * See the Guava User Guide article on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
 * immutable collections</a>.
 *
 * @author Jared Levy
 * @since 2.0 (imported from Google Collections Library)
 */
@GwtCompatible(serializable = true, emulated = true)
public class ImmutableListMultimap<K, V> extends ImmutableMultimap<K, V> implements ListMultimap<K, V> {

	/**
	 * A builder for creating immutable {@code ListMultimap} instances, especially
	 * {@code public static final} multimaps ("constant multimaps"). Example:
	 *
	 * <pre>
	 * {
	 * 	&#64;code
	 *
	 * 	static final Multimap<String, Integer> STRING_TO_INTEGER_MULTIMAP = new ImmutableListMultimap.Builder<String, Integer>()
	 * 			.put("one", 1).putAll("several", 1, 2, 3).putAll("many", 1, 2, 3, 4, 5).build();
	 * }
	 * </pre>
	 *
	 * <p>
	 * Builder instances can be reused; it is safe to call {@link #build} multiple
	 * times to build multiple multimaps in series. Each multimap contains the
	 * key-value mappings in the previously created multimaps.
	 *
	 * @since 2.0 (imported from Google Collections Library)
	 */
	public static final class Builder<K, V> extends ImmutableMultimap.Builder<K, V> {
		/**
		 * Creates a new builder. The returned builder is equivalent to the builder
		 * generated by {@link ImmutableListMultimap#builder}.
		 */
		public Builder() {
		}

		/**
		 * Returns a newly-created immutable list multimap.
		 */
		@Override
		public ImmutableListMultimap<K, V> build() {
			return (ImmutableListMultimap<K, V>) super.build();
		}

		/**
		 * {@inheritDoc}
		 *
		 * @since 8.0
		 */
		@Override
		public Builder<K, V> orderKeysBy(Comparator<? super K> keyComparator) {
			super.orderKeysBy(keyComparator);
			return this;
		}

		/**
		 * {@inheritDoc}
		 *
		 * @since 8.0
		 */
		@Override
		public Builder<K, V> orderValuesBy(Comparator<? super V> valueComparator) {
			super.orderValuesBy(valueComparator);
			return this;
		}

		/**
		 * {@inheritDoc}
		 *
		 * @since 11.0
		 */
		@Override
		public Builder<K, V> put(Entry<? extends K, ? extends V> entry) {
			super.put(entry);
			return this;
		}

		@Override
		public Builder<K, V> put(K key, V value) {
			super.put(key, value);
			return this;
		}

		@Override
		public Builder<K, V> putAll(K key, Iterable<? extends V> values) {
			super.putAll(key, values);
			return this;
		}

		@Override
		public Builder<K, V> putAll(K key, V... values) {
			super.putAll(key, values);
			return this;
		}

		@Override
		public Builder<K, V> putAll(Multimap<? extends K, ? extends V> multimap) {
			super.putAll(multimap);
			return this;
		}
	}

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

	/**
	 * Returns a new builder. The generated builder is equivalent to the builder
	 * created by the {@link Builder} constructor.
	 */
	public static <K, V> Builder<K, V> builder() {
		return new Builder<K, V>();
	}

	/**
	 * Returns an immutable multimap containing the same mappings as {@code
	 * multimap}. The generated multimap's key and value orderings correspond to the
	 * iteration ordering of the {@code multimap.asMap()} view.
	 *
	 * <p>
	 * Despite the method name, this method attempts to avoid actually copying the
	 * data when it is safe to do so. The exact circumstances under which a copy
	 * will or will not be performed are undocumented and subject to change.
	 *
	 * @throws NullPointerException if any key or value in {@code multimap} is null
	 */
	public static <K, V> ImmutableListMultimap<K, V> copyOf(Multimap<? extends K, ? extends V> multimap) {
		if (multimap.isEmpty()) {
			return of();
		}

		// TODO(user): copy ImmutableSetMultimap by using asList() on the sets
		if (multimap instanceof ImmutableListMultimap) {
			@SuppressWarnings("unchecked") // safe since multimap is not writable
			ImmutableListMultimap<K, V> kvMultimap = (ImmutableListMultimap<K, V>) multimap;
			if (!kvMultimap.isPartialView()) {
				return kvMultimap;
			}
		}

		ImmutableMap.Builder<K, ImmutableList<V>> builder = ImmutableMap.builder();
		int size = 0;

		for (Entry<? extends K, ? extends Collection<? extends V>> entry : multimap.asMap().entrySet()) {
			ImmutableList<V> list = ImmutableList.copyOf(entry.getValue());
			if (!list.isEmpty()) {
				builder.put(entry.getKey(), list);
				size += list.size();
			}
		}

		return new ImmutableListMultimap<K, V>(builder.build(), size);
	}

	/** Returns the empty multimap. */
	// Casting is safe because the multimap will never hold any elements.
	@SuppressWarnings("unchecked")
	public static <K, V> ImmutableListMultimap<K, V> of() {
		return (ImmutableListMultimap<K, V>) EmptyImmutableListMultimap.INSTANCE;
	}

	/**
	 * Returns an immutable multimap containing a single entry.
	 */
	public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1) {
		ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
		builder.put(k1, v1);
		return builder.build();
	}

	// looking for of() with > 5 entries? Use the builder instead.

	/**
	 * Returns an immutable multimap containing the given entries, in order.
	 */
	public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2) {
		ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
		builder.put(k1, v1);
		builder.put(k2, v2);
		return builder.build();
	}

	/**
	 * Returns an immutable multimap containing the given entries, in order.
	 */
	public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3) {
		ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
		builder.put(k1, v1);
		builder.put(k2, v2);
		builder.put(k3, v3);
		return builder.build();
	}

	/**
	 * Returns an immutable multimap containing the given entries, in order.
	 */
	public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
		ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
		builder.put(k1, v1);
		builder.put(k2, v2);
		builder.put(k3, v3);
		builder.put(k4, v4);
		return builder.build();
	}

	/**
	 * Returns an immutable multimap containing the given entries, in order.
	 */
	public static <K, V> ImmutableListMultimap<K, V> of(K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4, K k5, V v5) {
		ImmutableListMultimap.Builder<K, V> builder = ImmutableListMultimap.builder();
		builder.put(k1, v1);
		builder.put(k2, v2);
		builder.put(k3, v3);
		builder.put(k4, v4);
		builder.put(k5, v5);
		return builder.build();
	}

	// views

	private transient ImmutableListMultimap<V, K> inverse;

	ImmutableListMultimap(ImmutableMap<K, ImmutableList<V>> map, int size) {
		super(map, size);
	}

	/**
	 * Returns an immutable list of the values for the given key. If no mappings in
	 * the multimap have the provided key, an empty immutable list is returned. The
	 * values are in the same order as the parameters used to build this multimap.
	 */
	@Override
	public ImmutableList<V> get(@Nullable K key) {
		// This cast is safe as its type is known in constructor.
		ImmutableList<V> list = (ImmutableList<V>) map.get(key);
		return (list == null) ? ImmutableList.<V>of() : list;
	}

	/**
	 * {@inheritDoc}
	 *
	 * <p>
	 * Because an inverse of a list multimap can contain multiple pairs with the
	 * same key and value, this method returns an {@code
	 * ImmutableListMultimap} rather than the {@code ImmutableMultimap} specified in
	 * the {@code ImmutableMultimap} class.
	 *
	 * @since 11.0
	 */
	@Override
	public ImmutableListMultimap<V, K> inverse() {
		ImmutableListMultimap<V, K> result = inverse;
		return (result == null) ? (inverse = invert()) : result;
	}

	private ImmutableListMultimap<V, K> invert() {
		Builder<V, K> builder = builder();
		for (Entry<K, V> entry : entries()) {
			builder.put(entry.getValue(), entry.getKey());
		}
		ImmutableListMultimap<V, K> invertedMultimap = builder.build();
		invertedMultimap.inverse = this;
		return invertedMultimap;
	}

	@GwtIncompatible("java.io.ObjectInputStream")
	private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
		stream.defaultReadObject();
		int keyCount = stream.readInt();
		if (keyCount < 0) {
			throw new InvalidObjectException("Invalid key count " + keyCount);
		}
		ImmutableMap.Builder<Object, ImmutableList<Object>> builder = ImmutableMap.builder();
		int tmpSize = 0;

		for (int i = 0; i < keyCount; i++) {
			Object key = stream.readObject();
			int valueCount = stream.readInt();
			if (valueCount <= 0) {
				throw new InvalidObjectException("Invalid value count " + valueCount);
			}

			Object[] array = new Object[valueCount];
			for (int j = 0; j < valueCount; j++) {
				array[j] = stream.readObject();
			}
			builder.put(key, ImmutableList.copyOf(array));
			tmpSize += valueCount;
		}

		ImmutableMap<Object, ImmutableList<Object>> tmpMap;
		try {
			tmpMap = builder.build();
		} catch (IllegalArgumentException e) {
			throw (InvalidObjectException) new InvalidObjectException(e.getMessage()).initCause(e);
		}

		FieldSettersHolder.MAP_FIELD_SETTER.set(this, tmpMap);
		FieldSettersHolder.SIZE_FIELD_SETTER.set(this, tmpSize);
	}

	/**
	 * Guaranteed to throw an exception and leave the multimap unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public ImmutableList<V> removeAll(Object key) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Guaranteed to throw an exception and leave the multimap unmodified.
	 *
	 * @throws UnsupportedOperationException always
	 * @deprecated Unsupported operation.
	 */
	@Deprecated
	@Override
	public ImmutableList<V> replaceValues(K key, Iterable<? extends V> values) {
		throw new UnsupportedOperationException();
	}

	/**
	 * @serialData number of distinct keys, and then for each distinct key: the key,
	 *             the 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);
	}
}
