/*
    * Copyright (C) 2011 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.collect.BoundType.CLOSED;
  import static com.google.common.collect.BoundType.OPEN;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.collect.Multiset.Entry;
  
  import java.util.Comparator;
  import java.util.NoSuchElementException;
  import java.util.SortedSet;
  
  import javax.annotation.Nullable;
  
  /**
   * Provides static utility methods for creating and working with
   * {@link SortedMultiset} instances.
   *
   * @author Louis Wasserman
   */
  @GwtCompatible(emulated = true)
  final class SortedMultisets {
    private SortedMultisets() {
    }
  
    /**
     * A skeleton implementation for {@link SortedMultiset#elementSet}.
     */
    static class ElementSet<E> extends Multisets.ElementSet<E> implements
        SortedSet<E> {
      private final SortedMultiset<E> multiset;
  
      ElementSet(SortedMultiset<E> multiset) {
        this.multiset = multiset;
      }
  
      @Override final SortedMultiset<E> multiset() {
        return multiset;
      }
  
      @Override public Comparator<? super E> comparator() {
        return multiset().comparator();
      }
  
      @Override public SortedSet<E> subSet(E fromElement, E toElement) {
        return multiset().subMultiset(fromElement, CLOSED, toElement, OPEN).elementSet();
      }
  
      @Override public SortedSet<E> headSet(E toElement) {
        return multiset().headMultiset(toElement, OPEN).elementSet();
      }
  
      @Override public SortedSet<E> tailSet(E fromElement) {
        return multiset().tailMultiset(fromElement, CLOSED).elementSet();
      }
  
      @Override public E first() {
        return getElementOrThrow(multiset().firstEntry());
      }
  
      @Override public E last() {
        return getElementOrThrow(multiset().lastEntry());
      }
    }
  
    private static <E> E getElementOrThrow(Entry<E> entry) {
      if (entry == null) {
        throw new NoSuchElementException();
      }
      return entry.getElement();
    }
  
    private static <E> E getElementOrNull(@Nullable Entry<E> entry) {
      return (entry == null) ? null : entry.getElement();
    }
  }