/*

  * 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.convert;

 import javax.el.ELContext;

 import javax.el.ELException;

 import javax.el.ELResolver;

 import javax.el.PropertyNotFoundException;

 import javax.el.PropertyNotWritableException;

 import javax.faces.context.FacesContext;

 import javax.faces.el.EvaluationException;

 import javax.faces.el.VariableResolver;

 import java.beans.FeatureDescriptor;

 import java.util.Collection;

 import java.util.HashSet;

 import java.util.Iterator;

 import org.apache.myfaces.el.VariableResolverImpl;

 /**

  * Wrapper that converts a VariableResolver into an ELResolver. See JSF 1.2 spec section 5.6.1.5

  * 

  * @author Stan Silvert (latest modification by $Author$)

  * @author Mathias Broekelmann

  * @version $Revision$ $Date$

  */

 @SuppressWarnings("deprecation")

 public final class VariableResolverToELResolver extends ELResolver

 {

     // holds a flag to check if this instance is already called in current thread 

     private static final ThreadLocal<Collection<String>> propertyGuardThreadLocal

             = new ThreadLocal<Collection<String>>();

     /**

      * Gets the Collection<String> value of the propertyGuardThreadLocal.

      * If the value from the ThreadLocal ist null, a new Collection<String>

      * will be created.

      *

      * NOTE that we should not accomplish this by setting an initialValue on the

      * ThreadLocal, because this will automatically be set on the ThreadLocalMap

      * and thus can propably cause a memory leak.

      *

      * @return

      */

     private static Collection<String> getPropertyGuard()

     {

         Collection<String> propertyGuard = propertyGuardThreadLocal.get();

         if (propertyGuard == null)

         {

             propertyGuard = new HashSet<String>();

             propertyGuardThreadLocal.set(propertyGuard);

         }

         return propertyGuard;

     }

     private VariableResolver variableResolver;

     private boolean isDefaultLegacyVariableResolver;

     /**

      * Creates a new instance of VariableResolverToELResolver

      */

     public VariableResolverToELResolver(final VariableResolver variableResolver)

     {

         this.variableResolver = variableResolver;

         this.isDefaultLegacyVariableResolver = (this.variableResolver instanceof VariableResolverImpl);

     }

     /**

      * @return the variableResolver

      */

     public VariableResolver getVariableResolver()

     {

         return variableResolver;

     }

     @Override

     public Object getValue(ELContext context, Object base, Object property) throws NullPointerException,

             PropertyNotFoundException, ELException

     {

         if (isDefaultLegacyVariableResolver)

         {

             // Skip this one because it causes previous EL Resolvers already processed

             // before this one to be called again. This behavior is only valid if it 

             // is installed a custom VariableResolver.

             return null;

         }

         if (base != null)

         {

             return null;

         }

         if (property == null)

         {

             throw new PropertyNotFoundException();

         }

         context.setPropertyResolved(true);

         if (!(property instanceof String))

         {

             return null;

         }

         final String strProperty = (String) property;

         Collection<String> propertyGuard = getPropertyGuard();

         Object result = null;

         try

         {

             // only call the resolver if we haven't done it in current stack

             if(!propertyGuard.contains(strProperty))

             {

                 propertyGuard.add(strProperty);

                 result = variableResolver.resolveVariable(facesContext(context), strProperty);

             }

         }

         catch (javax.faces.el.PropertyNotFoundException e)

         {

             context.setPropertyResolved(false);

             throw new PropertyNotFoundException(e.getMessage(), e);

         }

         catch (EvaluationException e)

         {

             context.setPropertyResolved(false);

             throw new ELException(e.getMessage(), e);

         }

         catch (RuntimeException e)

         {

             context.setPropertyResolved(false);

             throw e;

         }

         finally

         {

             propertyGuard.remove(strProperty);

             // if the propertyGuard is empty, remove the ThreadLocal

             // in order to prevent a memory leak

             if (propertyGuard.isEmpty())

             {

                 propertyGuardThreadLocal.remove();

             }

             // set property resolved to false in any case if result is null

             context.setPropertyResolved(result != null);

         }

         return result;

     }

     // get the FacesContext from the ELContext

     private static FacesContext facesContext(ELContext context)

     {

         return (FacesContext) context.getContext(FacesContext.class);

     }

     @Override

     public Class<?> getCommonPropertyType(ELContext context, Object base)

     {

         if (isDefaultLegacyVariableResolver)

         {

             return null;

         }

         if (base != null)

         {

             return null;

         }

         return String.class;

     }

     @Override

     public void setValue(ELContext context, Object base, Object property, Object value) throws NullPointerException,

             PropertyNotFoundException, PropertyNotWritableException, ELException

     {

         if (isDefaultLegacyVariableResolver)

         {

             return;

         }

         if ((base == null) && (property == null))

         {

             throw new PropertyNotFoundException();

         }

     }

     @Override

     public boolean isReadOnly(ELContext context, Object base, Object property) throws NullPointerException,

             PropertyNotFoundException, ELException

     {

         if (isDefaultLegacyVariableResolver)

         {

             return false;

         }

         if ((base == null) && (property == null))

         {

             throw new PropertyNotFoundException();

         }

         return false;

     }

     @Override

     public Class<?> getType(ELContext context, Object base, Object property) throws NullPointerException,

             PropertyNotFoundException, ELException

     {

         if (isDefaultLegacyVariableResolver)

         {

             return null;

         }

         if ((base == null) && (property == null))

         {

             throw new PropertyNotFoundException();

         }

         return null;

     }

     @Override

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

     {

         if (isDefaultLegacyVariableResolver)

         {

             return null;

         }

         return null;

     }

 }