/*
    * 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 java.util.Collection;
  import java.util.Comparator;
  
  import javax.annotation.Nullable;
  
  /**
   * An empty immutable sorted multiset.
   *
   * @author Louis Wasserman
   */
  @SuppressWarnings("serial") // Uses writeReplace, not default serialization
  final class EmptyImmutableSortedMultiset<E> extends ImmutableSortedMultiset<E> {
    private final ImmutableSortedSet<E> elementSet;
  
    EmptyImmutableSortedMultiset(Comparator<? super E> comparator) {
      this.elementSet = ImmutableSortedSet.emptySet(comparator);
    }
  
    @Override
    public Entry<E> firstEntry() {
      return null;
    }
  
    @Override
    public Entry<E> lastEntry() {
      return null;
    }
  
    @Override
    public int count(@Nullable Object element) {
      return 0;
    }
  
    @Override
    public boolean containsAll(Collection<?> targets) {
      return targets.isEmpty();
    }
  
    @Override
    public int size() {
      return 0;
    }
  
    @Override
    public ImmutableSortedSet<E> elementSet() {
      return elementSet;
    }
  
    @Override
    Entry<E> getEntry(int index) {
      throw new AssertionError("should never be called");
    }
  
    @Override
    public ImmutableSortedMultiset<E> headMultiset(E upperBound, BoundType boundType) {
      checkNotNull(upperBound);
      checkNotNull(boundType);
      return this;
    }
  
    @Override
    public ImmutableSortedMultiset<E> tailMultiset(E lowerBound, BoundType boundType) {
      checkNotNull(lowerBound);
      checkNotNull(boundType);
      return this;
    }
  
    @Override
    public UnmodifiableIterator<E> iterator() {
      return Iterators.emptyIterator();
    }
  
    @Override
    public boolean equals(@Nullable Object object) {
      if (object instanceof Multiset) {
        Multiset<?> other = (Multiset<?>) object;
        return other.isEmpty();
      }
      return false;
    }
  
   @Override
   boolean isPartialView() {
     return false;
   }
 
   @Override
   int copyIntoArray(Object[] dst, int offset) {
     return offset;
   }
 
   @Override
   public ImmutableList<E> asList() {
     return ImmutableList.of();
   }
 }