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/*
 * JBoss, Home of Professional Open Source
 * Copyright 2008, Red Hat Middleware LLC, and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * Licensed 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.jboss.weld.environment.servlet.jsf;

import javax.el.ELContextListener;
import javax.el.ELResolver;
import javax.el.ExpressionFactory;
import javax.enterprise.inject.spi.BeanManager;
import javax.faces.application.Application;
import javax.faces.context.FacesContext;
import javax.servlet.ServletContext;

import org.jboss.weld.environment.servlet.util.ForwardingELResolver;
import org.jboss.weld.environment.servlet.util.Reflections;
import org.jboss.weld.environment.servlet.util.TransparentELResolver;

/**
 * @author Pete Muir
 * @author Dan Allen
 */
public class WeldApplication extends ForwardingApplication
{
   /**
    * The BeanManager may not have been initialized at the time JSF is initializing. Therefore,
    * we stick in a ForwardingELResolver that delegates to the BeanManager ELResolver, which will
    * be plugged in when it's available. If the ELResolver is invoked before the BeanManager
    * is available, the resolver will perform no action (and thus produce no result).
    */
   private static class LazyBeanManagerIntegrationELResolver extends ForwardingELResolver
   {
      private ELResolver delegate;

      public LazyBeanManagerIntegrationELResolver() {
         delegate = new TransparentELResolver();
      }
      
      public void beanManagerReady(BeanManager beanManager)
      {
         this.delegate = beanManager.getELResolver();
      }

      @Override
      protected ELResolver delegate()
      {
         return delegate;
      }
   }
   
   private final Application application;
   private LazyBeanManagerIntegrationELResolver elResolver;
   private ExpressionFactory expressionFactory;
   private BeanManager beanManager;
   
   public WeldApplication(Application application)
   {
      this.application = application;
      // QUESTION should the context listener be registered in init() instead?
      application.addELContextListener(Reflections.newInstance("org.jboss.weld.el.WeldELContextListener"));
      elResolver = new LazyBeanManagerIntegrationELResolver();
      application.addELResolver(elResolver);
   }
   
   private void init()
   {
      ExpressionFactory expressionFactory = null;
      BeanManager beanManager = null;
      if (expressionFactory == null && (expressionFactory = application.getExpressionFactory()) != null && (beanManager = beanManager()) != null)
      {
         elResolver.beanManagerReady(beanManager);
         this.expressionFactory = beanManager.wrapExpressionFactory(expressionFactory);
      }
   }

   @Override
   protected Application delegate()
   {
      init();
      return application;
   }
   
   @Override
   public ExpressionFactory getExpressionFactory()
   {
      init();
      if (expressionFactory == null)
      {
         return application.getExpressionFactory();
      }
      else
      {
         return expressionFactory;
      }
   }
   
   private BeanManager beanManager()
   {
      if (beanManager == null)
      {
         FacesContext facesContext = FacesContext.getCurrentInstance();
         if (!(facesContext.getExternalContext().getContext() instanceof ServletContext))
         {
            throw new IllegalStateException("Not in a servlet environment!");
         }
         ServletContext ctx = (ServletContext) facesContext.getExternalContext().getContext();
         if (ctx.getAttribute(BeanManager.class.getName()) == null)
         {
            return null;
         }
         this.beanManager = (BeanManager) ctx.getAttribute(BeanManager.class.getName());
      }
      
      return beanManager;
   }

}