/*
    * 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.reflect;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.Beta;
  import com.google.common.base.Function;
  import com.google.common.collect.ForwardingMap;
  import com.google.common.collect.ForwardingMapEntry;
  import com.google.common.collect.ForwardingSet;
  import com.google.common.collect.Iterators;
  import com.google.common.collect.Maps;
  
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Set;
  
  import javax.annotation.Nullable;
  
  /**
   * A mutable type-to-instance map.
   * See also {@link ImmutableTypeToInstanceMap}.
   *
   * @author Ben Yu
   * @since 13.0
   */
  @Beta
  public final class MutableTypeToInstanceMap<B> extends ForwardingMap<TypeToken<? extends B>, B>
      implements TypeToInstanceMap<B> {
  
    private final Map<TypeToken<? extends B>, B> backingMap = Maps.newHashMap();
  
    @Nullable
    @Override
    public <T extends B> T getInstance(Class<T> type) {
      return trustedGet(TypeToken.of(type));
    }
  
    @Nullable
    @Override
    public <T extends B> T putInstance(Class<T> type, @Nullable T value) {
      return trustedPut(TypeToken.of(type), value);
    }
  
    @Nullable
    @Override
    public <T extends B> T getInstance(TypeToken<T> type) {
      return trustedGet(type.rejectTypeVariables());
    }
  
    @Nullable
    @Override
    public <T extends B> T putInstance(TypeToken<T> type, @Nullable T value) {
      return trustedPut(type.rejectTypeVariables(), value);
    }
  
    /** Not supported. Use {@link #putInstance} instead. */
    @Override public B put(TypeToken<? extends B> key, B value) {
      throw new UnsupportedOperationException("Please use putInstance() instead.");
    }
  
    /** Not supported. Use {@link #putInstance} instead. */
    @Override public void putAll(Map<? extends TypeToken<? extends B>, ? extends B> map) {
      throw new UnsupportedOperationException("Please use putInstance() instead.");
    }
  
    @Override public Set<Entry<TypeToken<? extends B>, B>> entrySet() {
      return UnmodifiableEntry.transformEntries(super.entrySet());
    }
  
    @Override protected Map<TypeToken<? extends B>, B> delegate() {
      return backingMap;
    }
  
    @SuppressWarnings("unchecked") // value could not get in if not a T
    @Nullable
    private <T extends B> T trustedPut(TypeToken<T> type, @Nullable T value) {
      return (T) backingMap.put(type, value);
    }
  
    @SuppressWarnings("unchecked") // value could not get in if not a T
    @Nullable
    private <T extends B> T trustedGet(TypeToken<T> type) {
      return (T) backingMap.get(type);
   }
 
   private static final class UnmodifiableEntry<K, V> extends ForwardingMapEntry<K, V> {
 
     private final Entry<K, V> delegate;
 
     static <K, V> Set<Entry<K, V>> transformEntries(final Set<Entry<K, V>> entries) {
       return new ForwardingSet<Map.Entry<K, V>>() {
         @Override protected Set<Entry<K, V>> delegate() {
           return entries;
         }
         @Override public Iterator<Entry<K, V>> iterator() {
           return UnmodifiableEntry.transformEntries(super.iterator());
         }
         @Override public Object[] toArray() {
           return standardToArray();
         }
         @Override public <T> T[] toArray(T[] array) {
           return standardToArray(array);
         }
       };
     }
   
     private static <K, V> Iterator<Entry<K, V>> transformEntries(Iterator<Entry<K, V>> entries) {
       return Iterators.transform(entries, new Function<Entry<K, V>, Entry<K, V>>() {
         @Override public Entry<K, V> apply(Entry<K, V> entry) {
           return new UnmodifiableEntry<K, V>(entry);
         }
       });
     }
 
     private UnmodifiableEntry(java.util.Map.Entry<K, V> delegate) {
       this.delegate = checkNotNull(delegate);
     }
 
     @Override protected Entry<K, V> delegate() {
       return delegate;
     }
 
     @Override public V setValue(V value) {
       throw new UnsupportedOperationException();
     }
   }
 }