/*
    * 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.unified.resolver;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  
  import javax.el.ELContext;
  import javax.el.ELException;
  import javax.el.PropertyNotFoundException;
  
  import org.apache.myfaces.shared.util.ClassUtils;
  
  /**
   * See JSF 2.2 section 5.6.2.8
   */
  public class ImportHandlerResolver extends ScopedAttributeResolver
  {
      private static final Class EL_CLASS;
      private static final Constructor EL_CLASS_CONSTRUCTOR;
      private static final Method GET_IMPORT_HANDLER_METHOD;
      private static final Method IMPORT_HANDLER_RESOLVE_CLASS_METHOD;
      
      static
      {
          Class elClass = null;
          Class importHandlerClass = null;
          Constructor elClassConstructor = null;
          Method getImportHandlerMethod = null;
          Method importHandlerResolveClassMethod = null;
          try
          {
              // These classes will only be available with EL 3+
              elClass = ClassUtils.classForName("javax.el.ELClass");
              importHandlerClass = ClassUtils.classForName("javax.el.ImportHandler");
              getImportHandlerMethod = ELContext.class.getMethod("getImportHandler");
              if (elClass != null && importHandlerClass != null) 
              {
                  importHandlerResolveClassMethod = 
                      importHandlerClass.getDeclaredMethod("resolveClass", new Class[] {String.class});
                  elClassConstructor = elClass.getConstructor(Class.class);
              }
          }
          catch (SecurityException ex)
          {
              //No op
          }
          catch (ClassNotFoundException ex)
          {
              //No op
          } 
          catch (NoSuchMethodException e) 
          {
              // No op
          }
          EL_CLASS = elClass;
          GET_IMPORT_HANDLER_METHOD = getImportHandlerMethod;
          IMPORT_HANDLER_RESOLVE_CLASS_METHOD = importHandlerResolveClassMethod;
          EL_CLASS_CONSTRUCTOR = elClassConstructor;
      }
      
      /**
       * Creates a new instance of ImportHandlerResolver
       */
      public ImportHandlerResolver()
      {
      }
  
      /*
       * Handle the EL case for the name of an import class
       */
      @Override
      public Object getValue(final ELContext context, final Object base, final Object property)
          throws NullPointerException, PropertyNotFoundException, ELException
      {
          if (EL_CLASS != null && EL_CLASS_CONSTRUCTOR != null 
                          && GET_IMPORT_HANDLER_METHOD != null && IMPORT_HANDLER_RESOLVE_CLASS_METHOD != null ) 
          {
              Object importHandler = null;
              try 
              {
                  // In an EL 3+ environment, the ELContext will have a getImportHandler() method
                 importHandler = GET_IMPORT_HANDLER_METHOD.invoke(context);
                 if (importHandler != null) 
                 {
                     Class<?> clazz;
                     clazz = (Class<?>) IMPORT_HANDLER_RESOLVE_CLASS_METHOD
                         .invoke(importHandler, property.toString());
                     if (clazz != null) 
                     {
                         context.setPropertyResolved(true);
                         return EL_CLASS_CONSTRUCTOR.newInstance(clazz);
                     }
                 }
             } 
             catch (IllegalAccessException ex) 
             {
                 //No op
             } 
             catch (IllegalArgumentException ex) 
             {
                 //No op
             } 
             catch (InvocationTargetException ex) 
             {
                 //No op
             } 
             catch (SecurityException ex) 
             {
                 //No op
             } 
             catch (InstantiationException e) 
             {
                 //No op
             }
         }
         return null;
     }
 }