/*
    * 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.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Comparator;
  import java.util.SortedSet;
  
  /**
   * Utilities for dealing with sorted collections of all types.
   *
   * @author Louis Wasserman
   */
  @GwtCompatible
  final class SortedIterables {
    private SortedIterables() {}
  
    /**
     * Returns {@code true} if {@code elements} is a sorted collection using an ordering equivalent
     * to {@code comparator}.
     */
    public static boolean hasSameComparator(Comparator<?> comparator, Iterable<?> elements) {
      checkNotNull(comparator);
      checkNotNull(elements);
      Comparator<?> comparator2;
      if (elements instanceof SortedSet) {
        comparator2 = comparator((SortedSet<?>) elements);
      } else if (elements instanceof SortedIterable) {
        comparator2 = ((SortedIterable<?>) elements).comparator();
      } else {
        return false;
      }
      return comparator.equals(comparator2);
    }
  
    @SuppressWarnings("unchecked")
    // if sortedSet.comparator() is null, the set must be naturally ordered
    public static <E> Comparator<? super E> comparator(SortedSet<E> sortedSet) {
      Comparator<? super E> result = sortedSet.comparator();
      if (result == null) {
        result = (Comparator<? super E>) Ordering.natural();
      }
      return result;
    }
  }