/*

  * $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();

         }

     }

 }