/*
 * 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 com.google.common.annotations.GwtCompatible;

import java.util.Collection;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * Basic implementation of the {@link SetMultimap} interface. It's a wrapper
 * around {@link AbstractMapBasedMultimap} that converts the returned collections into
 * {@code Sets}. The {@link #createCollection} method must return a {@code Set}.
 *
 * @author Jared Levy
 */
@GwtCompatible
abstract class AbstractSetMultimap<K, V>
    extends AbstractMapBasedMultimap<K, V> implements SetMultimap<K, V> {
  /**
   * Creates a new multimap that uses the provided map.
   *
   * @param map place to store the mapping from each key to its corresponding
   *     values
   */
  protected AbstractSetMultimap(Map<K, Collection<V>> map) {
    super(map);
  }

  @Override abstract Set<V> createCollection();

  @Override Set<V> createUnmodifiableEmptyCollection() {
    return ImmutableSet.of();
  }

  // Following Javadoc copied from SetMultimap.

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this
   * method returns a {@link Set}, instead of the {@link Collection} specified
   * in the {@link Multimap} interface.
   */
  @Override public Set<V> get(@Nullable K key) {
    return (Set<V>) super.get(key);
  }

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this
   * method returns a {@link Set}, instead of the {@link Collection} specified
   * in the {@link Multimap} interface.
   */
  @Override public Set<Map.Entry<K, V>> entries() {
    return (Set<Map.Entry<K, V>>) super.entries();
  }

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this
   * method returns a {@link Set}, instead of the {@link Collection} specified
   * in the {@link Multimap} interface.
   */
  @Override public Set<V> removeAll(@Nullable Object key) {
    return (Set<V>) super.removeAll(key);
  }

  /**
   * {@inheritDoc}
   *
   * <p>Because a {@code SetMultimap} has unique values for a given key, this
   * method returns a {@link Set}, instead of the {@link Collection} specified
   * in the {@link Multimap} interface.
   *
   * <p>Any duplicates in {@code values} will be stored in the multimap once.
   */
  @Override public Set<V> replaceValues(
      @Nullable K key, Iterable<? extends V> values) {
    return (Set<V>) super.replaceValues(key, values);
  }

  /**
   * {@inheritDoc}
   *
   * <p>Though the method signature doesn't say so explicitly, the returned map
   * has {@link Set} values.
   */
  @Override public Map<K, Collection<V>> asMap() {
    return super.asMap();
  }

  /**
   * Stores a key-value pair in the multimap.
   *
   * @param key key to store in the multimap
   * @param value value to store in the multimap
   * @return {@code true} if the method increased the size of the multimap, or
   *     {@code false} if the multimap already contained the key-value pair
   */
  @Override public boolean put(@Nullable K key, @Nullable V value) {
    return super.put(key, value);
  }

  /**
   * Compares the specified object to this multimap for equality.
   *
   * <p>Two {@code SetMultimap} instances are equal if, for each key, they
   * contain the same values. Equality does not depend on the ordering of keys
   * or values.
   */
  @Override public boolean equals(@Nullable Object object) {
    return super.equals(object);
  }

  private static final long serialVersionUID = 7431625294878419160L;
}