/*
    * 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.Beta;
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Comparator;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  import java.util.SortedSet;
  
  import javax.annotation.Nullable;
  
  /**
   * A sorted set which forwards all its method calls to another sorted set.
   * Subclasses should override one or more methods to modify the behavior of the
   * backing sorted set as desired per the <a
   * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
   *
   * <p><i>Warning:</i> The methods of {@code ForwardingSortedSet} forward
   * <i>indiscriminately</i> to the methods of the delegate. For example,
   * overriding {@link #add} alone <i>will not</i> 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>Each of the {@code standard} methods, where appropriate, uses the set's
   * comparator (or the natural ordering of the elements, if there is no
   * comparator) to test element equality. As a result, if the comparator is not
   * consistent with equals, some of the standard implementations may violate the
   * {@code Set} contract.
   *
   * <p>The {@code standard} methods and the collection views they return are not
   * guaranteed to be thread-safe, even when all of the methods that they depend
   * on are thread-safe.
   *
   * @author Mike Bostock
   * @author Louis Wasserman
   * @since 2.0 (imported from Google Collections Library)
   */
  @GwtCompatible
  public abstract class ForwardingSortedSet<E> extends ForwardingSet<E>
      implements SortedSet<E> {
  
    /** Constructor for use by subclasses. */
    protected ForwardingSortedSet() {}
  
    @Override protected abstract SortedSet<E> delegate();
  
    @Override
    public Comparator<? super E> comparator() {
      return delegate().comparator();
    }
  
    @Override
    public E first() {
      return delegate().first();
    }
  
    @Override
    public SortedSet<E> headSet(E toElement) {
      return delegate().headSet(toElement);
    }
  
    @Override
    public E last() {
      return delegate().last();
    }
  
    @Override
    public SortedSet<E> subSet(E fromElement, E toElement) {
      return delegate().subSet(fromElement, toElement);
    }
  
    @Override
    public SortedSet<E> tailSet(E fromElement) {
      return delegate().tailSet(fromElement);
    }
  
    // unsafe, but worst case is a CCE is thrown, which callers will be expecting
    @SuppressWarnings("unchecked")
    private int unsafeCompare(Object o1, Object o2) {
      Comparator<? super E> comparator = comparator();
      return (comparator == null)
         ? ((Comparable<Object>) o1).compareTo(o2)
         : ((Comparator<Object>) comparator).compare(o1, o2);
   }
 
   /**
    * A sensible definition of {@link #contains} in terms of the {@code first()}
    * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish
    * to override {@link #contains} to forward to this implementation.
    *
    * @since 7.0
    */
   @Override @Beta protected boolean standardContains(@Nullable Object object) {
     try {
       // any ClassCastExceptions are caught
       @SuppressWarnings("unchecked")
       SortedSet<Object> self = (SortedSet<Object>) this;
       Object ceiling = self.tailSet(object).first();
       return unsafeCompare(ceiling, object) == 0;
     } catch (ClassCastException e) {
       return false;
     } catch (NoSuchElementException e) {
       return false;
     } catch (NullPointerException e) {
       return false;
     }
   }
 
   /**
    * A sensible definition of {@link #remove} in terms of the {@code iterator()}
    * method of {@link #tailSet}. If you override {@link #tailSet}, you may wish
    * to override {@link #remove} to forward to this implementation.
    *
    * @since 7.0
    */
   @Override @Beta protected boolean standardRemove(@Nullable Object object) {
     try {
       // any ClassCastExceptions are caught
       @SuppressWarnings("unchecked")
       SortedSet<Object> self = (SortedSet<Object>) this;
       Iterator<Object> iterator = self.tailSet(object).iterator();
       if (iterator.hasNext()) {
         Object ceiling = iterator.next();
         if (unsafeCompare(ceiling, object) == 0) {
           iterator.remove();
           return true;
         }
       }
     } catch (ClassCastException e) {
       return false;
     } catch (NullPointerException e) {
       return false;
     }
     return false;
   }
 
   /**
    * A sensible default implementation of {@link #subSet(Object, Object)} in
    * terms of {@link #headSet(Object)} and {@link #tailSet(Object)}. In some
    * situations, you may wish to override {@link #subSet(Object, Object)} to
    * forward to this implementation.
    *
    * @since 7.0
    */
   @Beta protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
     return tailSet(fromElement).headSet(toElement);
   }
 }