/*
    * Copyright (C) 2007 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.base.Objects;
  
  import java.util.Collection;
  import java.util.Iterator;
  
  import javax.annotation.Nullable;
  
  /**
   * A collection which forwards all its method calls to another collection.
   * Subclasses should override one or more methods to modify the behavior of the
   * backing collection as desired per the <a
   * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
   *
   * <p><b>Warning:</b> The methods of {@code ForwardingCollection} forward
   * <b>indiscriminately</b> to the methods of the delegate. For example,
   * overriding {@link #add} alone <b>will not</b> change the behavior of {@link
   * #addAll}, which can lead to unexpected behavior. In this case, you should
   * override {@code addAll} as well, either providing your own implementation, or
   * delegating to the provided {@code standardAddAll} method.
   *
   * <p>The {@code standard} methods are not guaranteed to be thread-safe, even
   * when all of the methods that they depend on are thread-safe.
   *
   * @author Kevin Bourrillion
   * @author Louis Wasserman
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible
  public abstract class ForwardingCollection<E> extends ForwardingObject
      implements Collection<E> {
    // TODO(user): identify places where thread safety is actually lost
  
    /** Constructor for use by subclasses. */
    protected ForwardingCollection() {}
  
    @Override protected abstract Collection<E> delegate();
  
    @Override
    public Iterator<E> iterator() {
      return delegate().iterator();
    }
  
    @Override
    public int size() {
      return delegate().size();
    }
  
    @Override
    public boolean removeAll(Collection<?> collection) {
      return delegate().removeAll(collection);
    }
  
    @Override
    public boolean isEmpty() {
      return delegate().isEmpty();
    }
  
    @Override
    public boolean contains(Object object) {
      return delegate().contains(object);
    }
  
    @Override
    public boolean add(E element) {
      return delegate().add(element);
    }
  
    @Override
    public boolean remove(Object object) {
      return delegate().remove(object);
    }
  
    @Override
    public boolean containsAll(Collection<?> collection) {
      return delegate().containsAll(collection);
    }
  
    @Override
    public boolean addAll(Collection<? extends E> collection) {
      return delegate().addAll(collection);
   }
 
   @Override
   public boolean retainAll(Collection<?> collection) {
     return delegate().retainAll(collection);
   }
 
   @Override
   public void clear() {
     delegate().clear();
   }
 
   @Override
   public Object[] toArray() {
     return delegate().toArray();
   }
 
   @Override
   public <T> T[] toArray(T[] array) {
     return delegate().toArray(array);
   }
 
   /**
    * A sensible definition of {@link #contains} in terms of {@link #iterator}.
    * If you override {@link #iterator}, you may wish to override {@link
    * #contains} to forward to this implementation.
    *
    * @since 7.0
    */
   protected boolean standardContains(@Nullable Object object) {
     return Iterators.contains(iterator(), object);
   }
 
   /**
    * A sensible definition of {@link #containsAll} in terms of {@link #contains}
    * . If you override {@link #contains}, you may wish to override {@link
    * #containsAll} to forward to this implementation.
    *
    * @since 7.0
    */
   protected boolean standardContainsAll(Collection<?> collection) {
     return Collections2.containsAllImpl(this, collection);
   }
 
   /**
    * A sensible definition of {@link #addAll} in terms of {@link #add}. If you
    * override {@link #add}, you may wish to override {@link #addAll} to forward
    * to this implementation.
    *
    * @since 7.0
    */
   protected boolean standardAddAll(Collection<? extends E> collection) {
     return Iterators.addAll(this, collection.iterator());
   }
 
   /**
    * A sensible definition of {@link #remove} in terms of {@link #iterator},
    * using the iterator's {@code remove} method. If you override {@link
    * #iterator}, you may wish to override {@link #remove} to forward to this
    * implementation.
    *
    * @since 7.0
    */
   protected boolean standardRemove(@Nullable Object object) {
     Iterator<E> iterator = iterator();
     while (iterator.hasNext()) {
       if (Objects.equal(iterator.next(), object)) {
         iterator.remove();
         return true;
       }
     }
     return false;
   }
 
   /**
    * A sensible definition of {@link #removeAll} in terms of {@link #iterator},
    * using the iterator's {@code remove} method. If you override {@link
    * #iterator}, you may wish to override {@link #removeAll} to forward to this
    * implementation.
    *
    * @since 7.0
    */
   protected boolean standardRemoveAll(Collection<?> collection) {
     return Iterators.removeAll(iterator(), collection);
   }
 
   /**
    * A sensible definition of {@link #retainAll} in terms of {@link #iterator},
    * using the iterator's {@code remove} method. If you override {@link
    * #iterator}, you may wish to override {@link #retainAll} to forward to this
    * implementation.
    *
    * @since 7.0
    */
   protected boolean standardRetainAll(Collection<?> collection) {
     return Iterators.retainAll(iterator(), collection);
   }
 
   /**
    * A sensible definition of {@link #clear} in terms of {@link #iterator},
    * using the iterator's {@code remove} method. If you override {@link
    * #iterator}, you may wish to override {@link #clear} to forward to this
    * implementation.
    *
    * @since 7.0
    */
   protected void standardClear() {
     Iterators.clear(iterator());
   }
 
   /**
    * A sensible definition of {@link #isEmpty} as {@code !iterator().hasNext}.
    * If you override {@link #isEmpty}, you may wish to override {@link #isEmpty}
    * to forward to this implementation. Alternately, it may be more efficient to
    * implement {@code isEmpty} as {@code size() == 0}.
    *
    * @since 7.0
    */
   protected boolean standardIsEmpty() {
     return !iterator().hasNext();
   }
 
   /**
    * A sensible definition of {@link #toString} in terms of {@link #iterator}.
    * If you override {@link #iterator}, you may wish to override {@link
    * #toString} to forward to this implementation.
    *
    * @since 7.0
    */
   protected String standardToString() {
     return Collections2.toStringImpl(this);
   }
 
   /**
    * A sensible definition of {@link #toArray()} in terms of {@link
    * #toArray(Object[])}. If you override {@link #toArray(Object[])}, you may
    * wish to override {@link #toArray} to forward to this implementation.
    *
    * @since 7.0
    */
   protected Object[] standardToArray() {
     Object[] newArray = new Object[size()];
     return toArray(newArray);
   }
 
   /**
    * A sensible definition of {@link #toArray(Object[])} in terms of {@link
    * #size} and {@link #iterator}. If you override either of these methods, you
    * may wish to override {@link #toArray} to forward to this implementation.
    *
    * @since 7.0
    */
   protected <T> T[] standardToArray(T[] array) {
     return ObjectArrays.toArrayImpl(this, array);
   }
 }