/*
    * $Id: TilesContextBeanELResolver.java 1291847 2012-02-21 15:09:30Z nlebas $
    *
    * 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.tiles.el;
  
  import java.beans.FeatureDescriptor;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import javax.el.ELContext;
  import javax.el.ELResolver;
  
  import org.apache.tiles.request.Request;
  
  /**
   * Resolves beans in request, session and application scope.
   *
   * @version $Rev: 1291847 $ $Date: 2012-02-22 02:09:30 +1100 (Wed, 22 Feb 2012) $
   * @since 2.2.1
   */
  public class TilesContextBeanELResolver extends ELResolver {
  
      /** {@inheritDoc} */
      @Override
      public Class<?> getCommonPropertyType(ELContext context, Object base) {
          // only resolve at the root of the context
          if (base != null) {
              return null;
          }
  
          return String.class;
      }
  
      /** {@inheritDoc} */
      @Override
      public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context,
              Object base) {
          List<FeatureDescriptor> list = new ArrayList<FeatureDescriptor>();
  
          Request request = (Request) context
                  .getContext(Request.class);
          for (String scope : request.getAvailableScopes()) {
              collectBeanInfo(request.getContext(scope), list);
          }
          return list.iterator();
      }
  
      /** {@inheritDoc} */
      @Override
      public Class<?> getType(ELContext context, Object base, Object property) {
          if (base != null) {
              return null;
          }
  
          Object obj = findObjectByProperty(context, property);
          if (obj != null) {
              context.setPropertyResolved(true);
              return obj.getClass();
          }
          return null;
      }
  
      /** {@inheritDoc} */
      @Override
      public Object getValue(ELContext context, Object base, Object property) {
          if (base != null) {
              return null;
          }
  
          Object retValue = findObjectByProperty(context, property);
  
          if (retValue != null) {
              context.setPropertyResolved(true);
          }
  
          return retValue;
      }
  
      /** {@inheritDoc} */
      @Override
     public boolean isReadOnly(ELContext context, Object base, Object property) {
         if (context == null) {
             throw new NullPointerException();
         }
 
         return true;
     }
 
     /** {@inheritDoc} */
     @Override
     public void setValue(ELContext context, Object base, Object property,
             Object value) {
         // Does nothing for the moment.
     }
 
     /**
      * Collects bean infos from a map's values and filling a list.
      *
      * @param map The map containing the bean to be inspected.
      * @param list The list to fill.
      * @since 2.2.1
      */
     protected void collectBeanInfo(Map<String, ? extends Object> map,
             List<FeatureDescriptor> list) {
         if (map == null || map.isEmpty()) {
             return;
         }
 
         for (Map.Entry<String, ? extends Object> entry : map.entrySet()) {
             FeatureDescriptor descriptor = new FeatureDescriptor();
             descriptor.setDisplayName(entry.getKey());
             descriptor.setExpert(false);
             descriptor.setHidden(false);
             descriptor.setName(entry.getKey());
             descriptor.setPreferred(true);
             descriptor.setShortDescription("");
             descriptor.setValue("type", String.class);
             descriptor.setValue("resolvableAtDesignTime", Boolean.FALSE);
             list.add(descriptor);
         }
     }
 
     /**
      * Finds an object in request, session or application scope, in this order.
      *
      * @param context The context to use.
      * @param property The property used as an attribute name.
      * @return The found bean, if it exists, or <code>null</code> otherwise.
      * @since 2.2.1
      */
     protected Object findObjectByProperty(ELContext context, Object property) {
         Object retValue = null;
 
         Request request = (Request) context
                 .getContext(Request.class);
 
         String prop = property.toString();
 
         String[] scopes = request.getAvailableScopes().toArray(new String[0]);
         int i = 0;
         do {
             retValue = getObject(request.getContext(scopes[i]), prop);
             i++;
         } while (retValue == null && i < scopes.length);
 
         return retValue;
     }
 
     /**
      * Returns an object from a map in a null-safe manner.
      *
      * @param map The map to use.
      * @param property The property to use as a key.
      * @return The object, if present, or <code>null</code> otherwise.
      * @since 2.2.1
      */
     protected Object getObject(Map<String, ? extends Object> map,
             String property) {
         Object retValue = null;
         if (map != null) {
             retValue = map.get(property);
         }
         return retValue;
     }
 }