// Copyright 2006, 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.internal.transform;

 import org.apache.tapestry5.annotations.Persist;

 import org.apache.tapestry5.ioc.util.BodyBuilder;

 import org.apache.tapestry5.model.MutableComponentModel;

 import org.apache.tapestry5.services.*;

 import java.lang.reflect.Modifier;

 /**

  * Converts fields with the {@link org.apache.tapestry5.annotations.Persist} annotation into persistent fields.

  */

 public class PersistWorker implements ComponentClassTransformWorker

 {

     public void transform(ClassTransformation transformation, MutableComponentModel model)

     {

         for (String name : transformation.findFieldsWithAnnotation(Persist.class))

         {

             makeFieldPersistent(name, transformation, model);

         }

     }

     /**

      * Making a field persistent: <ul> <li>Need a secondary default field that stores the initial value</li> <li>Store

      * the active value into the default field when the page finishes loading</li> <li>Roll the active value back to the

      * default when the page detaches</li> <ii>On changes to the active field, post the change via the {@link

      * org.apache.tapestry5.internal.InternalComponentResources} </li> <li>When the page attaches, pull the persisted

      * value for the field out of the {@link org.apache.tapestry5.services.PersistentFieldBundle}</li> </ul>

      *

      * @see org.apache.tapestry5.runtime.PageLifecycleListener#restoreStateBeforePageAttach()

      */

     private void makeFieldPersistent(String fieldName, ClassTransformation transformation,

                                      MutableComponentModel model)

     {

         String fieldType = transformation.getFieldType(fieldName);

         Persist annotation = transformation.getFieldAnnotation(fieldName, Persist.class);

         transformation.claimField(fieldName, annotation);

         // Record the type of persistence, until needed later.

         String logicalFieldName = model.setFieldPersistenceStrategy(fieldName, annotation.value());

         String defaultValue = TransformUtils.getDefaultValue(fieldType);

         // Force the field back to its default value (null, 0, false) at the end of each request.

         transformation.extendMethod(

                 TransformConstants.CONTAINING_PAGE_DID_DETACH_SIGNATURE,

                 String.format("%s = %s;", fieldName, defaultValue));

         String resourcesFieldName = transformation.getResourcesFieldName();

         String writeMethodName = transformation.newMemberName("write", fieldName);

         BodyBuilder builder = new BodyBuilder();

         builder.begin();

         builder.addln(

                 "%s.persistFieldChange(\"%s\", ($w) $1);",

                 resourcesFieldName,

                 logicalFieldName);

         builder.addln("%s = $1;", fieldName);

         builder.end();

         transformation.addMethod(new TransformMethodSignature(Modifier.PRIVATE, "void", writeMethodName,

                                                               new String[]

                                                                       { fieldType }, null), builder.toString());

         transformation.replaceWriteAccess(fieldName, writeMethodName);

         builder.clear();

         builder.begin();

         // Check to see if there's a recorded change for this component, this field.

         builder.addln("if (%s.hasFieldChange(\"%s\"))", resourcesFieldName, logicalFieldName);

         String wrapperType = TransformUtils.getWrapperTypeName(fieldType);

         // Get the value, cast it to the correct type (or wrapper type)

         builder.add(

                 "  %s = ((%s) %s.getFieldChange(\"%s\"))",

                 fieldName,

                 wrapperType,

                 resourcesFieldName,

                 logicalFieldName);

         // For primtive types, add in the method call to unwrap the wrapper type to a primitive type

         String unwrapMethodName = TransformUtils.getUnwrapperMethodName(fieldType);

         if (unwrapMethodName == null)

             builder.addln(";");

         else

             builder.addln(".%s();", unwrapMethodName);

         builder.end();

         transformation.extendMethod(

                 TransformConstants.RESTORE_STATE_BEFORE_PAGE_ATTACH_SIGNATURE,

                 builder.toString());

     }

 }