/*
    * 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 static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Comparator;
  
  import javax.annotation.Nullable;
  
  /**
   * An empty immutable sorted map.
   *
   * @author Louis Wasserman
   */
  @GwtCompatible(emulated = true)
  @SuppressWarnings("serial") // uses writeReplace, not default serialization
  final class EmptyImmutableSortedMap<K, V> extends ImmutableSortedMap<K, V> {
    private final transient ImmutableSortedSet<K> keySet;
  
    EmptyImmutableSortedMap(Comparator<? super K> comparator) {
      this.keySet = ImmutableSortedSet.emptySet(comparator);
    }
  
    EmptyImmutableSortedMap(
        Comparator<? super K> comparator, ImmutableSortedMap<K, V> descendingMap) {
      super(descendingMap);
      this.keySet = ImmutableSortedSet.emptySet(comparator);
    }
  
    @Override
    public V get(@Nullable Object key) {
      return null;
    }
  
    @Override
    public ImmutableSortedSet<K> keySet() {
      return keySet;
    }
  
    @Override
    public int size() {
      return 0;
    }
  
    @Override
    public boolean isEmpty() {
      return true;
    }
  
    @Override
    public ImmutableCollection<V> values() {
      return ImmutableList.of();
    }
  
    @Override
    public String toString() {
      return "{}";
    }
  
    @Override
    boolean isPartialView() {
      return false;
    }
  
    @Override
    public ImmutableSet<Entry<K, V>> entrySet() {
      return ImmutableSet.of();
    }
  
    @Override
    ImmutableSet<Entry<K, V>> createEntrySet() {
      throw new AssertionError("should never be called");
    }
  
    @Override
    public ImmutableSetMultimap<K, V> asMultimap() {
      return ImmutableSetMultimap.of();
    }
  
    @Override
    public ImmutableSortedMap<K, V> headMap(K toKey, boolean inclusive) {
      checkNotNull(toKey);
      return this;
   }
 
   @Override
   public ImmutableSortedMap<K, V> tailMap(K fromKey, boolean inclusive) {
     checkNotNull(fromKey);
     return this;
   }
 
   @Override
   ImmutableSortedMap<K, V> createDescendingMap() {
     return new EmptyImmutableSortedMap<K, V>(Ordering.from(comparator()).reverse(), this);
   }
 }