package org.apache.turbine.modules;

 /*

  * 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.

  */

 import java.util.ArrayList;

 import java.util.List;

 import org.apache.turbine.Turbine;

 import org.apache.turbine.TurbineConstants;

 import org.apache.turbine.pipeline.PipelineData;

 import org.apache.turbine.services.TurbineServices;

 import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;

 /**

  * This is the base class for the loaders. It contains code that is

  * used across all of the loaders. It also specifies the interface

  * that is required to be called a Loader.

  *

  * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>

  * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>

  * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>

  * @param <T> the specialized assembler type

  */

 public abstract class GenericLoader<T extends Assembler>

 {

     /** The Assembler Broker Service */

     protected AssemblerBrokerService ab;

     /** @serial This can be serialized */

     private boolean reload = false;

     /** Base packages path for Turbine */

     private static final String TURBINE_PACKAGE = "org.apache.turbine.modules";

     /** Packages paths for Turbine */

     private static List<String> TURBINE_PACKAGES = null;

     /**

      * Basic constructor for creating a loader.

      */

     public GenericLoader()

     {

         super();

         ab = (AssemblerBrokerService)TurbineServices.getInstance().getService(AssemblerBrokerService.SERVICE_NAME);

     }

     /**

      * Attempts to load and execute the external action that has been

      * set.

      * @param pipelineData the Turbine request

      * @param name the name of the assembler module

      * @throws Exception a generic exception.

      */

     public abstract void exec(PipelineData pipelineData, String name)

             throws Exception;

     /**

      * Returns whether or not this external action is reload itself.

      * This is in cases where the Next button would be clicked, but

      * since we are checking for that, we would go into an endless

      * loop.

      *

      * @return True if the action is reload.

      */

     public boolean reload()

     {

         return this.reload;

     }

     /**

      * Sets whether or not this external action is reload itself.

      * This is in cases where the Next button would be clicked, but

      * since we are checking for that, we would go into an endless

      * loop.

      *

      * @param reload True if the action must be marked as reload.

      * @return Itself.

      */

     public GenericLoader<T> setReload(boolean reload)

     {

         this.reload = reload;

         return this;

     }

     /**

      * Gets the base package where Turbine should find its default

      * modules.

      *

      * @return A String with the base package name.

      */

     public static String getBasePackage()

     {

         return TURBINE_PACKAGE;

     }

     /**

      * Gets the package list where Turbine should find its

      * modules.

      *

      * @return A List with the package names (including the base package).

      */

     public static List<String> getPackages()

     {

         if (TURBINE_PACKAGES == null)

         {

             List<String> turbinePackages = new ArrayList<String>();

             List<Object> configTurbinePackages =

                 Turbine.getConfiguration()

                         .getList(TurbineConstants.MODULE_PACKAGES);

             for (Object o : configTurbinePackages)

             {

                     turbinePackages.add((String)o);

             }

             TURBINE_PACKAGES = turbinePackages;

         }

         List<String> packages = TURBINE_PACKAGES;

         if (!packages.contains(TURBINE_PACKAGE))

         {

             packages.add(TURBINE_PACKAGE);

         }

         return packages;

     }

     /**

      * Pulls out an instance of the object by name.  Name is just the

      * single name of the object.

      *

      * @param type Type of the assembler.

      * @param name Name of object instance.

      * @return A Screen with the specified name, or null.

      * @throws Exception a generic exception.

      */

     protected T getAssembler(Class<T> type, String name)

         throws Exception

     {

         T asm = null;

         try

         {

             if (ab != null)

             {

                 // Attempt to load the assembler

                 asm = ab.getAssembler(type, name);

             }

         }

         catch (ClassCastException cce)

         {

             // This can alternatively let this exception be thrown

             // So that the ClassCastException is shown in the

             // browser window.  Like this it shows "Screen not Found"

             asm = null;

         }

         if (asm == null)

         {

             // If we did not find a screen we should try and give

             // the user a reason for that...

             // FIX ME: The AssemblerFactories should each add it's

             // own string here...

             List<String> packages = GenericLoader.getPackages();

             throw new ClassNotFoundException(

                     "\n\n\tRequested " + type + " not found: " + name +

                     "\n\tTurbine looked in the following " +

                     "modules.packages path: \n\t" + packages.toString() + "\n");

         }

         return asm;

     }

 }