/*

  * $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;

     }

 }