// Copyright 2007, 2008, 2009 The Apache Software Foundation

 //

 // 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.apache.tapestry5.corelib.base;

 import org.apache.tapestry5.Block;

 import org.apache.tapestry5.MarkupWriter;

 import org.apache.tapestry5.PropertyConduit;

 import org.apache.tapestry5.PropertyOverrides;

 import org.apache.tapestry5.annotations.Parameter;

 import org.apache.tapestry5.beaneditor.PropertyModel;

 import org.apache.tapestry5.ioc.Messages;

 import org.apache.tapestry5.ioc.annotations.Inject;

 import org.apache.tapestry5.ioc.internal.util.InternalUtils;

 import org.apache.tapestry5.services.BeanBlockSource;

 import org.apache.tapestry5.services.Core;

 import org.apache.tapestry5.services.Environment;

 import org.apache.tapestry5.services.PropertyOutputContext;

 /**

  * Base class for components that output a property value using a {@link PropertyModel}. There's a relationship between

  * such a component and its container, as the container may provide messages in its message catalog needed by the {@link

  * Block}s that render the values. In addition, the component may be passed Block parameters that are output overrides

  * for specified properties.

  * <p/>

  * Subclasses will implement a <code>beginRender()</code> method that invokes {@link #renderPropertyValue(MarkupWriter,

  * String)}.

  *

  * @see BeanBlockSource

  */

 public abstract class AbstractPropertyOutput

 {

     /**

      * Model for property displayed by the cell.

      */

     @Parameter(required = true, allowNull = false)

     private PropertyModel model;

     /**

      * Used to search for block parameter overrides (this is normally the enclosing Grid component's resources).

      */

     @Parameter(required = true, allowNull = false)

     private PropertyOverrides overrides;

     /**

      * Identifies the object being rendered. The component will extract a property from the object and render its value

      * (or delegate to a {@link org.apache.tapestry5.Block} that will do so).

      */

     @Parameter(required = true)

     private Object object;

     /**

      * Source for property display blocks. This defaults to the default implementation of {@link

      * org.apache.tapestry5.services.BeanBlockSource}.

      */

     @Parameter(required = true, allowNull = false)

     private BeanBlockSource beanBlockSource;

     @Inject

     @Core

     private BeanBlockSource defaultBeanBlockSource;

     @Inject

     private Environment environment;

     private boolean mustPopEnvironment;

     BeanBlockSource defaultBeanBlockSource()

     {

         return defaultBeanBlockSource;

     }

     protected PropertyModel getPropertyModel()

     {

         return model;

     }

     /**

      * Invoked from subclasses to do the rendering. The subclass controls the naming convention for locating an

      * overriding Block parameter (it is the name of the property possibly suffixed with a value).

      */

     protected Object renderPropertyValue(MarkupWriter writer, String overrideBlockId)

     {

         Block override = overrides.getOverrideBlock(overrideBlockId);

         if (override != null) return override;

         String datatype = model.getDataType();

         if (beanBlockSource.hasDisplayBlock(datatype))

         {

             PropertyOutputContext context = new PropertyOutputContext()

             {

                 public Messages getMessages()

                 {

                     return overrides.getOverrideMessages();

                 }

                 public Object getPropertyValue()

                 {

                     return readPropertyForObject();

                 }

                 public String getPropertyId()

                 {

                     return model.getId();

                 }

                 public String getPropertyName()

                 {

                     return model.getPropertyName();

                 }

             };

             environment.push(PropertyOutputContext.class, context);

             mustPopEnvironment = true;

             return beanBlockSource.getDisplayBlock(datatype);

         }

         Object value = readPropertyForObject();

         String text = value == null ? "" : value.toString();

         if (InternalUtils.isNonBlank(text))

         {

             writer.write(text);

         }

         // Don't render anything else

         return false;

     }

     Object readPropertyForObject()

     {

         PropertyConduit conduit = model.getConduit();

         try

         {

             return conduit == null ? null : conduit.get(object);

         }

         catch (NullPointerException ex)

         {

             throw new NullPointerException(BaseMessages.nullValueInPath(model.getPropertyName()));

         }

     }

     /**

      * Returns false; there's no template and this prevents the body from rendering.

      */

     boolean beforeRenderTemplate()

     {

         return false;

     }

     void afterRender()

     {

         if (mustPopEnvironment)

         {

             environment.pop(PropertyOutputContext.class);

             mustPopEnvironment = false;

         }

     }

     // Used for testing.

     void inject(final PropertyModel model, final Object object)

     {

         this.model = model;

         this.object = object;

     }

 }