/*
    * Copyright (C) 2008 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.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  
  import java.util.Collection;
  import java.util.Comparator;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  import javax.annotation.Nullable;
  
  /**
   * An empty immutable sorted set.
   *
   * @author Jared Levy
   */
  @GwtCompatible(serializable = true, emulated = true)
  @SuppressWarnings("serial") // uses writeReplace(), not default serialization
  class EmptyImmutableSortedSet<E> extends ImmutableSortedSet<E> {
    EmptyImmutableSortedSet(Comparator<? super E> comparator) {
      super(comparator);
    }
  
    @Override
    public int size() {
      return 0;
    }
  
    @Override public boolean isEmpty() {
      return true;
    }
  
    @Override public boolean contains(@Nullable Object target) {
      return false;
    }
  
    @Override public boolean containsAll(Collection<?> targets) {
      return targets.isEmpty();
    }
  
    @Override public UnmodifiableIterator<E> iterator() {
      return Iterators.emptyIterator();
    }
  
    @GwtIncompatible("NavigableSet")
    @Override public UnmodifiableIterator<E> descendingIterator() {
      return Iterators.emptyIterator();
    }
  
    @Override boolean isPartialView() {
      return false;
    }
  
    @Override public ImmutableList<E> asList() {
      return ImmutableList.of();
    }
  
    @Override
    int copyIntoArray(Object[] dst, int offset) {
      return offset;
    }
  
    @Override public boolean equals(@Nullable Object object) {
      if (object instanceof Set) {
        Set<?> that = (Set<?>) object;
        return that.isEmpty();
      }
      return false;
    }
  
    @Override public int hashCode() {
      return 0;
    }
  
    @Override public String toString() {
      return "[]";
    }
  
    @Override
    public E first() {
      throw new NoSuchElementException();
    }
 
   @Override
   public E last() {
     throw new NoSuchElementException();
   }
 
   @Override
   ImmutableSortedSet<E> headSetImpl(E toElement, boolean inclusive) {
     return this;
   }
 
   @Override
   ImmutableSortedSet<E> subSetImpl(
       E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
     return this;
   }
 
   @Override
   ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {
     return this;
   }
 
   @Override int indexOf(@Nullable Object target) {
     return -1;
   }
 
   @Override
   ImmutableSortedSet<E> createDescendingSet() {
     return new EmptyImmutableSortedSet<E>(Ordering.from(comparator).reverse());
   }
 }