package org.apache.turbine.services.assemblerbroker.util.python;
   
   /*
    * 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.io.File;
  
  import org.apache.commons.configuration.Configuration;
  
  import org.apache.commons.lang.StringUtils;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  import org.apache.turbine.modules.Assembler;
  import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker;
  import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
  
  import org.python.core.Py;
  import org.python.util.PythonInterpreter;
  
  /***
   * A factory that attempts to load a python class in the
   * JPython interpreter and execute it as a Turbine screen.
   * The JPython script should inherit from Turbine Screen or one
   * of its subclasses.
   *
   * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
   * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
   * @version $Id: PythonBaseFactory.java 534527 2007-05-02 16:10:59Z tv $
   */
  public abstract class PythonBaseFactory
          implements AssemblerFactory
  {
      /*** Key for the python path */
      public static final String PYTHON_PATH = "python.path";
  
      /*** Global config file. This is executed before every screen */
      public static final String PYTHON_CONFIG_FILE = "conf.py";
  
      /*** Logging */
      private static Log log = LogFactory.getLog(PythonBaseFactory.class);
  
      /*** Our configuration */
      private Configuration conf =
          TurbineAssemblerBroker.getService().getConfiguration();
  
      /***
       * Get an Assembler.
       *
       * @param subDirectory subdirectory within python.path
       * @param name name of the requested Assembler
       * @return an Assembler
       * @throws Exception generic exception
       */
      public Assembler getAssembler(String subDirectory, String name)
              throws Exception
      {
          String path = conf.getString(PYTHON_PATH);
  
          if (StringUtils.isEmpty(path))
          {
              throw new Exception(
                  "Python path not found - check your Properties");
          }
  
          log.debug("Screen name for JPython: " + name);
  
          Assembler assembler = null;
  
          String confName = path + "/" + PYTHON_CONFIG_FILE;
  
          // The filename of the Python script
          StringBuffer fName = new StringBuffer();
  
          fName.append(path);
          fName.append("/");
          fName.append(subDirectory);
          fName.append("/");
          fName.append(name.toLowerCase());
          fName.append(".py");
  
          File f = new File(fName.toString());
 
         if (f.exists())
         {
             try
             {
                 // We try to open the Py Interpreter
                 PythonInterpreter interp = new PythonInterpreter();
 
                 // Make sure the Py Interpreter use the right classloader
                 // This is necessary for servlet engines generally has
                 // their own classloader implementations and servlets aren't
                 // loaded in the system classloader.  The python script will
                 // load java package
                 // org.apache.turbine.services.assemblerbroker.util.python;
                 // the new classes to it as well.
                 Py.getSystemState().setClassLoader(
                         this.getClass().getClassLoader());
 
                 // We import the Python SYS module. Now we don't need to do this
                 // explicitely in the script.  We always use the sys module to
                 // do stuff like loading java package
                 // org.apache.turbine.services.assemblerbroker.util.python;
                 interp.exec("import sys");
 
                 // Now we try to load the script file
                 interp.execfile(confName);
                 interp.execfile(fName.toString());
 
                 try
                 {
                     // We create an instance of the screen class from the
                     // python script
                     interp.exec("scr = " + name + "()");
                 }
                 catch (Throwable e)
                 {
                     throw new Exception(
                         "\nCannot create an instance of the python class.\n"
                         + "You probably gave your class the wrong name.\n"
                         + "Your class should have the same name as your "
                         + "filename.\nFilenames should be all lowercase and "
                         + "classnames should start with a capital.\n"
                         + "Expected class name: " + name + "\n");
                 }
 
                 // Here we convert the python sceen instance to a java instance.
                 assembler = (Assembler) interp.get("scr", Assembler.class);
             }
             catch (Exception e)
             {
                 // We log the error here because this code is not widely tested
                 // yet. After we tested the code on a range of platforms this
                 // won't be usefull anymore.
                 log.error("PYTHON SCRIPT SCREEN LOADER ERROR:", e);
                 throw e;
             }
         }
         return assembler;
     }
 }