/*
    * 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.io.Serializable;
  import java.util.Map.Entry;
  
  import javax.annotation.Nullable;
  
  /**
   * {@code keySet()} implementation for {@link ImmutableMap}.
   *
   * @author Jesse Wilson
   * @author Kevin Bourrillion
   */
  @GwtCompatible(emulated = true)
  final class ImmutableMapKeySet<K, V> extends ImmutableSet<K> {
    private final ImmutableMap<K, V> map;
  
    ImmutableMapKeySet(ImmutableMap<K, V> map) {
      this.map = map;
    }
  
    @Override
    public int size() {
      return map.size();
    }
  
    @Override
    public UnmodifiableIterator<K> iterator() {
      return asList().iterator();
    }
  
    @Override
    public boolean contains(@Nullable Object object) {
      return map.containsKey(object);
    }
  
    @Override
    ImmutableList<K> createAsList() {
      final ImmutableList<Entry<K, V>> entryList = map.entrySet().asList();
      return new ImmutableAsList<K>() {
  
        @Override
        public K get(int index) {
          return entryList.get(index).getKey();
        }
  
        @Override
        ImmutableCollection<K> delegateCollection() {
          return ImmutableMapKeySet.this;
        }
  
      };
    }
  
    @Override
    boolean isPartialView() {
      return true;
    }
  
    @GwtIncompatible("serialization")
    @Override Object writeReplace() {
      return new KeySetSerializedForm<K>(map);
    }
  
    @GwtIncompatible("serialization")
    private static class KeySetSerializedForm<K> implements Serializable {
      final ImmutableMap<K, ?> map;
      KeySetSerializedForm(ImmutableMap<K, ?> map) {
        this.map = map;
      }
      Object readResolve() {
        return map.keySet();
      }
      private static final long serialVersionUID = 0;
    }
  }