/*

  * 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.shared.view;

 import javax.faces.application.Application;

 import javax.faces.application.ViewHandler;

 import javax.faces.component.UIViewRoot;

 import javax.faces.context.FacesContext;

 import javax.faces.view.ViewDeclarationLanguage;

 import org.apache.myfaces.shared.application.InvalidViewIdException;

 /**

  * @since 2.0

  */

 public abstract class ViewDeclarationLanguageBase extends ViewDeclarationLanguage

 {

     /**

      * Process the specification required algorithm that is generic to all PDL.

      * 

      * @param context

      * @param viewId

      */

     public UIViewRoot createView(FacesContext context, String viewId)

     {

         checkNull(context, "context");

         //checkNull(viewId, "viewId");

         try

         {

             viewId = calculateViewId(context, viewId);

             Application application = context.getApplication();

             // Create a new UIViewRoot object instance using Application.createComponent(UIViewRoot.COMPONENT_TYPE).

             UIViewRoot newViewRoot = (UIViewRoot) application.createComponent(

                 context, UIViewRoot.COMPONENT_TYPE, null);

             UIViewRoot oldViewRoot = context.getViewRoot();

             if (oldViewRoot == null)

             {

                 // If not, this method must call calculateLocale() and calculateRenderKitId(), and store the results

                 // as the values of the locale and renderKitId, proeprties, respectively, of the newly created

                 // UIViewRoot.

                 ViewHandler handler = application.getViewHandler();

                 newViewRoot.setLocale(handler.calculateLocale(context));

                 newViewRoot.setRenderKitId(handler.calculateRenderKitId(context));

             }

             else

             {

                 // If there is an existing UIViewRoot available on the FacesContext, this method must copy its locale

                 // and renderKitId to this new view root

                 newViewRoot.setLocale(oldViewRoot.getLocale());

                 newViewRoot.setRenderKitId(oldViewRoot.getRenderKitId());

             }

             // TODO: VALIDATE - The spec is silent on the following line, but I feel bad if I don't set it

             newViewRoot.setViewId(viewId);

             return newViewRoot;

         }

         catch (InvalidViewIdException e)

         {

             // If no viewId could be identified, or the viewId is exactly equal to the servlet mapping, 

             // send the response error code SC_NOT_FOUND with a suitable message to the client.

             sendSourceNotFound(context, e.getMessage());

             // TODO: VALIDATE - Spec is silent on the return value when an error was sent

             return null;

         }

     }

     /**

      * {@inheritDoc}

      */

     @Override

     public UIViewRoot restoreView(FacesContext context, String viewId)

     {

         checkNull(context, "context");

         //checkNull(viewId, "viewId");

         Application application = context.getApplication();

         ViewHandler applicationViewHandler = application.getViewHandler();

         String renderKitId = applicationViewHandler.calculateRenderKitId(context);

         UIViewRoot viewRoot = application.getStateManager().restoreView(context, viewId, renderKitId);

         return viewRoot;

     }

     /**

      * Calculates the effective view identifier for the specified raw view identifier.

      * 

      * @param context le current FacesContext

      * @param viewId the raw view identifier

      * 

      * @return the effective view identifier

      */

     protected abstract String calculateViewId(FacesContext context, String viewId);

     /**

      * Send a source not found to the client. Although it can be considered ok in JSP mode,

      * I think it's pretty lame to have this kind of requirement at VDL level considering VDL 

      * represents the page --> JSF tree link, not the transport layer required to send a 

      * SC_NOT_FOUND.

      * 

      * @param context le current FacesContext

      * @param message the message associated with the error

      */

     protected abstract void sendSourceNotFound(FacesContext context, String message);

     /**

      * Check if the specified value of a param is <code>null</code>.

      * 

      * @param o the parameter's value

      * @param param the parameter's name

      * 

      * @throws NullPointerException if the value is <code>null</code>

      */

     protected void checkNull(final Object o, final String param)

     {

         if (o == null)

         {

             throw new NullPointerException(param + " can not be null.");

         }

     }

 }