/*
 * 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.checkArgument;

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

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Iterator;

/**
 * Multiset implementation backed by an {@link EnumMap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset">
 * {@code Multiset}</a>.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class EnumMultiset<E extends Enum<E>> extends AbstractMapBasedMultiset<E> {
  /** Creates an empty {@code EnumMultiset}. */
  public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) {
    return new EnumMultiset<E>(type);
  }

  /**
   * Creates a new {@code EnumMultiset} containing the specified elements.
   *
   * <p>This implementation is highly efficient when {@code elements} is itself a {@link
   * Multiset}.
   *
   * @param elements the elements that the multiset should contain
   * @throws IllegalArgumentException if {@code elements} is empty
   */
  public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
    Iterator<E> iterator = elements.iterator();
    checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
    EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next().getDeclaringClass());
    Iterables.addAll(multiset, elements);
    return multiset;
  }

  /**
   * Returns a new {@code EnumMultiset} instance containing the given elements.  Unlike
   * {@link EnumMultiset#create(Iterable)}, this method does not produce an exception on an empty
   * iterable.
   *
   * @since 14.0
   */
  public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements, Class<E> type) {
    EnumMultiset<E> result = create(type);
    Iterables.addAll(result, elements);
    return result;
  }

  private transient Class<E> type;

  /** Creates an empty {@code EnumMultiset}. */
  private EnumMultiset(Class<E> type) {
    super(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
    this.type = type;
  }

  @GwtIncompatible // java.io.ObjectOutputStream
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(type);
    Serialization.writeMultiset(this, stream);
  }

  /**
   * @serialData the {@code Class<E>} for the enum type, the number of distinct
   *             elements, the first element, its count, the second element, its
   *             count, and so on
   */
  @GwtIncompatible // java.io.ObjectInputStream
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    Class<E> localType = (Class<E>) stream.readObject();
    type = localType;
    setBackingMap(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
    Serialization.populateMultiset(this, stream);
  }

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