/*
    * Copyright (C) 2012 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.GwtIncompatible;
  
  import javax.annotation.Nullable;
  
  /**
   * Skeletal implementation of {@link ImmutableSortedSet#descendingSet()}.
   *
   * @author Louis Wasserman
   */
  class DescendingImmutableSortedSet<E> extends ImmutableSortedSet<E> {
    private final ImmutableSortedSet<E> forward;
  
    DescendingImmutableSortedSet(ImmutableSortedSet<E> forward) {
      super(Ordering.from(forward.comparator()).reverse());
      this.forward = forward;
    }
  
    @Override
    public int size() {
      return forward.size();
    }
  
    @Override
    public UnmodifiableIterator<E> iterator() {
      return forward.descendingIterator();
    }
  
    @Override
    ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive) {
      return forward.tailSet(toElement, inclusive).descendingSet();
    }
  
    @Override
    ImmutableSortedSet<E> subSetImpl(
        E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
      return forward.subSet(toElement, toInclusive, fromElement, fromInclusive).descendingSet();
    }
  
    @Override
    ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {
      return forward.headSet(fromElement, inclusive).descendingSet();
    }
  
    @Override
    @GwtIncompatible("NavigableSet")
    public ImmutableSortedSet<E> descendingSet() {
      return forward;
    }
  
    @Override
    @GwtIncompatible("NavigableSet")
    public UnmodifiableIterator<E> descendingIterator() {
      return forward.iterator();
    }
  
    @Override
    @GwtIncompatible("NavigableSet")
    ImmutableSortedSet<E> createDescendingSet() {
      throw new AssertionError("should never be called");
    }
  
    @Override
    public E lower(E element) {
      return forward.higher(element);
    }
  
    @Override
    public E floor(E element) {
      return forward.ceiling(element);
    }
  
    @Override
    public E ceiling(E element) {
      return forward.floor(element);
    }
  
    @Override
    public E higher(E element) {
      return forward.lower(element);
    }
  
   @Override
   int indexOf(@Nullable Object target) {
     int index = forward.indexOf(target);
     if (index == -1) {
       return index;
     } else {
       return size() - 1 - index;
     }
   }
 
   @Override
   boolean isPartialView() {
     return forward.isPartialView();
   }
 }