/*
    * 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 java.util.EnumMap;
  import java.util.Iterator;
  
  /**
   * Multiset implementation backed by an {@link EnumMap}.
   * 
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
   * {@code Multiset}</a>.
   *
   * @author Jared Levy
   * @since 2.0 (imported from Google Collections Library)
   */
  @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;
    }
  }