/*
    * 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.myfaces.util;
  
  import java.util.AbstractMap;
  import java.util.AbstractSet;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Enumeration;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  /**
   * Helper Map implementation for use with different Attribute Maps.
   * 
   * @author Anton Koinov (latest modification by $Author$)
   * @version $Revision$ $Date$
   */
  public abstract class AbstractThreadSafeAttributeMap<V> extends AbstractMap<String, V>
  {
      private Set<String> _keySet = new KeySet();
      private Collection<V> _values =  new Values();
      private Set<Entry<String, V>> _entrySet = new EntrySet();
  
      @Override
      public void clear()
      {
          final List<String> names = Collections.list(getAttributeNames());
  
          for (String name : names)
          {
              removeAttribute(name);
          }
      }
  
      @Override
      public final boolean containsKey(final Object key)
      {
          return getAttribute(key.toString()) != null;
      }
  
      @Override
      public boolean containsValue(final Object findValue)
      {
          if (findValue == null)
          {
              return false;
          }
  
          for (final Enumeration<String> e = getAttributeNames(); e.hasMoreElements();)
          {
              final Object value = getAttribute(e.nextElement());
              if (findValue.equals(value))
              {
                  return true;
              }
          }
  
          return false;
      }
  
      @Override
      public Set<Entry<String, V>> entrySet()
      {
          return _entrySet;
      }
  
      @Override
      public V get(final Object key)
      {
          return getAttribute(key.toString());
      }
  
      @Override
      public boolean isEmpty()
      {
          return !getAttributeNames().hasMoreElements();
      }
  
      @Override
     public Set<String> keySet()
     {
         return _keySet;
     }
 
     @Override
     public final V put(final String key, final V value)
     {
         final V retval = getAttribute(key);
         setAttribute(key, value);
         return retval;
     }
 
     @Override
     public void putAll(final Map<? extends String, ? extends V> t)
     {
         for (final Entry<? extends String, ? extends V> entry : t.entrySet())
         {
             setAttribute(entry.getKey(), entry.getValue());
         }
     }
 
     @Override
     public final V remove(final Object key)
     {
         final String keyString = key.toString();
         final V retval = getAttribute(keyString);
         removeAttribute(keyString);
         return retval;
     }
 
     @Override
     public int size()
     {
         int size = 0;
         for (final Enumeration<String> e = getAttributeNames(); e.hasMoreElements();)
         {
             size++;
             e.nextElement();
         }
         return size;
     }
 
     @Override
     public Collection<V> values()
     {
         return _values;
     }
 
     abstract protected V getAttribute(String key);
 
     abstract protected void setAttribute(String key, V value);
 
     abstract protected void removeAttribute(String key);
 
     abstract protected Enumeration<String> getAttributeNames();
 
     private abstract class AbstractAttributeSet<E> extends AbstractSet<E>
     {
         @Override
         public boolean isEmpty()
         {
             return AbstractThreadSafeAttributeMap.this.isEmpty();
         }
 
         @Override
         public int size()
         {
             return AbstractThreadSafeAttributeMap.this.size();
         }
 
         @Override
         public void clear()
         {
             AbstractThreadSafeAttributeMap.this.clear();
         }
     }
 
     private final class KeySet extends AbstractAttributeSet<String>
     {
         @Override
         public Iterator<String> iterator()
         {
             return new KeyIterator();
         }
 
         @Override
         public boolean contains(final Object o)
         {
             return AbstractThreadSafeAttributeMap.this.containsKey(o);
         }
 
         @Override
         public boolean remove(final Object o)
         {
             return AbstractThreadSafeAttributeMap.this.remove(o) != null;
         }
 
     }
 
     private abstract class AbstractAttributeIterator<E> implements Iterator<E>
     {
         // We use a copied version of the Enumeration from getAttributeNames()
         // here, because directly using it might cause a ConcurrentModificationException
         // when performing remove(). Note that we can do this since the Enumeration
         // from getAttributeNames() will contain exactly the attribute names from the time
         // getAttributeNames() was called and it will not be updated if attributes are 
         // removed or added.
         protected final Iterator<String> _i = Collections.list(getAttributeNames()).iterator();
         protected String _currentKey;
 
         public void remove()
         {
             if (_currentKey == null)
             {
                 throw new NoSuchElementException("You must call next() at least once");
             }
             AbstractThreadSafeAttributeMap.this.remove(_currentKey);
         }
 
         public boolean hasNext()
         {
             return _i.hasNext();
         }
 
         public E next()
         {
             _currentKey = _i.next();
             return getValue(_currentKey);
         }
 
         protected abstract E getValue(String attributeName);
     }
 
     private final class KeyIterator extends AbstractAttributeIterator<String>
     {
         @Override
         protected String getValue(final String attributeName)
         {
             return attributeName;
         }
     }
 
     private class Values extends AbstractAttributeSet<V>
     {
         @Override
         public Iterator<V> iterator()
         {
             return new ValuesIterator();
         }
 
         @Override
         public boolean contains(final Object o)
         {
             if (o == null)
             {
                 return false;
             }
 
             for (final Iterator<V> it = iterator(); it.hasNext();)
             {
                 if (o.equals(it.next()))
                 {
                     return true;
                 }
             }
 
             return false;
         }
 
         @Override
         public boolean remove(final Object o)
         {
             if (o == null)
             {
                 return false;
             }
 
             for (final Iterator<V> it = iterator(); it.hasNext();)
             {
                 if (o.equals(it.next()))
                 {
                     it.remove();
                     return true;
                 }
             }
 
             return false;
         }
     }
 
     private class ValuesIterator extends AbstractAttributeIterator<V>
     {
         @Override
         protected V getValue(final String attributeName)
         {
             return AbstractThreadSafeAttributeMap.this.get(attributeName);
         }
     }
 
     private final class EntrySet extends AbstractAttributeSet<Entry<String, V>>
     {
         @Override
         public Iterator<Entry<String, V>> iterator()
         {
             return new EntryIterator();
         }
 
         @SuppressWarnings("unchecked")
         @Override
         public boolean contains(final Object o)
         {
             if (!(o instanceof Entry))
             {
                 return false;
             }
 
             final Entry<String, V> entry = (Entry<String, V>)o;
             final Object key = entry.getKey();
             final Object value = entry.getValue();
             if (key == null || value == null)
             {
                 return false;
             }
 
             return value.equals(AbstractThreadSafeAttributeMap.this.get(key));
         }
 
         @SuppressWarnings("unchecked")
         @Override
         public boolean remove(final Object o)
         {
             if (!(o instanceof Entry))
             {
                 return false;
             }
 
             final Entry<String, V> entry = (Entry<String, V>)o;
             final Object key = entry.getKey();
             final Object value = entry.getValue();
             if (key == null || value == null || !value.equals(AbstractThreadSafeAttributeMap.this.get(key)))
             {
                 return false;
             }
 
             return AbstractThreadSafeAttributeMap.this.remove(((Entry<String, V>)o).getKey()) != null;
         }
     }
 
     /**
      * Not very efficient since it generates a new instance of <code>Entry</code> for each element and still internaly
      * uses the <code>KeyIterator</code>. It is more efficient to use the <code>KeyIterator</code> directly.
      */
     private final class EntryIterator extends AbstractAttributeIterator<Entry<String, V>>
     {
         @Override
         protected Entry<String, V> getValue(final String attributeName)
         {
             // Must create new Entry every time--value of the entry must stay
             // linked to the same attribute name
             return new EntrySetEntry(attributeName);
         }
     }
 
     private final class EntrySetEntry implements Entry<String, V>
     {
         private final String _currentKey;
 
         public EntrySetEntry(final String currentKey)
         {
             _currentKey = currentKey;
         }
 
         public String getKey()
         {
             return _currentKey;
         }
 
         public V getValue()
         {
             return AbstractThreadSafeAttributeMap.this.get(_currentKey);
         }
 
         public V setValue(final V value)
         {
             return AbstractThreadSafeAttributeMap.this.put(_currentKey, value);
         }
 
         @Override
         public int hashCode()
         {
             int result = 1;
             result = 31 * result + ((_currentKey == null) ? 0 : _currentKey.hashCode());
             return result;
         }
 
         @Override
         public boolean equals(final Object obj)
         {
             if (this == obj)
             {
                 return true;
             }
             if (obj == null)
             {
                 return false;
             }
             if (getClass() != obj.getClass())
             {
                 return false;
             }
             final EntrySetEntry other = (EntrySetEntry)obj;
             if (_currentKey == null)
             {
                 if (other._currentKey != null)
                 {
                     return false;
                 }
             }
             else if (!_currentKey.equals(other._currentKey))
             {
                 return false;
             }
             return true;
         }
 
     }
 }