/*
    * $Id: KeySet.java 1229087 2012-01-09 10:35:14Z mck $
    *
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.tiles.request.collection;
  
  import static org.apache.tiles.request.collection.CollectionUtil.*;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.tiles.request.attribute.HasKeys;
  
  /**
   * Exposes keys of a {@link HasKeys} object as a set.
   *
   * @version $Rev: 1229087 $ $Date: 2012-01-09 21:35:14 +1100 (Mon, 09 Jan 2012) $
   */
  public class KeySet implements Set<String> {
  
      /**
       * The request to read.
       */
      private HasKeys<?> request;
  
      /**
       * Constructor.
       *
       * @param request The request to read.
       */
      public KeySet(HasKeys<?> request) {
          this.request = request;
      }
  
      @Override
      public boolean add(String e) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean addAll(Collection<? extends String> c) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public void clear() {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean contains(Object o) {
          return request.getValue(key(o)) != null;
      }
  
      @SuppressWarnings("unchecked")
      @Override
      public boolean containsAll(Collection<?> c) {
          Collection<String> realCollection = (Collection<String>) c;
          for (String key : realCollection) {
              if (request.getValue(key(key)) == null) {
                  return false;
              }
          }
          return true;
      }
  
      @Override
      public boolean isEmpty() {
          return !request.getKeys().hasMoreElements();
      }
  
      @Override
      public Iterator<String> iterator() {
          return new KeySetIterator();
      }
  
      @Override
      public boolean remove(Object o) {
          throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean removeAll(Collection<?> c) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public boolean retainAll(Collection<?> c) {
         throw new UnsupportedOperationException();
     }
 
     @Override
     public int size() {
         return enumerationSize(request.getKeys());
     }
 
     @Override
     public Object[] toArray() {
         return toList().toArray();
     }
 
     @Override
     public <T> T[] toArray(T[] a) {
         return toList().toArray(a);
     }
 
     /**
      * Turns this set into a list.
      *
      * @return The corresponding list.
      */
     private List<String> toList() {
         List<String> entries = new ArrayList<String>();
         Enumeration<String> names = request.getKeys();
         while (names.hasMoreElements()) {
             entries.add(names.nextElement());
         }
         return entries;
     }
 
     /**
      * Iterates elements of {@link KeySet}.
      */
     private class KeySetIterator implements Iterator<String> {
 
         /**
          * The key names enumeration.
          */
         private Enumeration<String> namesEnumeration = request.getKeys();
 
         @Override
         public boolean hasNext() {
             return namesEnumeration.hasMoreElements();
         }
 
         @Override
         public String next() {
             return namesEnumeration.nextElement();
         }
 
         @Override
         public void remove() {
             throw new UnsupportedOperationException();
         }
     }
 }