/*

  * 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.el;

 import java.beans.FeatureDescriptor;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.Collections;

 import java.util.Iterator;

 import java.util.NoSuchElementException;

 import javax.el.ELContext;

 import javax.el.ELResolver;

 /**

  * @author Mathias Broekelmann (latest modification by $Author$)

  * @version $Revision$ $Date$

  */

 public class CompositeELResolver extends javax.el.CompositeELResolver

 {

     private Collection<ELResolver> _elResolvers;

     @Override

     public Iterator<FeatureDescriptor> getFeatureDescriptors(final ELContext context, final Object base)

     {

         Collection<ELResolver> resolvers = _elResolvers;

         if (resolvers == null)

         {

             resolvers = Collections.emptyList();

         }

         return new CompositeIterator(context, base, resolvers.iterator());

     }

     /**

      * @param elResolver

      */

     @Override

     public final synchronized void add(final ELResolver elResolver)

     {

         super.add(elResolver);

         if (_elResolvers == null)

         {

             _elResolvers = new ArrayList<ELResolver>();

         }

         _elResolvers.add(elResolver);

     }

     private static class CompositeIterator implements Iterator<FeatureDescriptor>

     {

         private final ELContext _context;

         private final Object _base;

         private final Iterator<ELResolver> _elResolvers;

         private FeatureDescriptor _nextFD;

         private Iterator<FeatureDescriptor> _currentFDIter;

         public CompositeIterator(final ELContext context, final Object base, final Iterator<ELResolver> elResolvers)

         {

             _context = context;

             _base = base;

             _elResolvers = elResolvers;

         }

         public boolean hasNext()

         {

             if (_nextFD != null)

             {

                 return true;

             }

             if (_currentFDIter != null)

             {

                 while (_nextFD == null && _currentFDIter.hasNext())

                 {

                     _nextFD = _currentFDIter.next();

                 }

             }

             if (_nextFD == null)

             {

                 if (_elResolvers.hasNext())

                 {

                     _currentFDIter = _elResolvers.next().getFeatureDescriptors(_context, _base);

                 }

                 else

                 {

                     return false;

                 }

             }

             return hasNext();

         }

         public FeatureDescriptor next()

         {

             if (!hasNext())

             {

                 throw new NoSuchElementException();

             }

             FeatureDescriptor next = _nextFD;

             _nextFD = null;

             return next;

         }

         public void remove()

         {

             throw new UnsupportedOperationException();

         }

     }

 }