/*

  * 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.giraph.jython;

 import org.apache.giraph.graph.Language;

 import org.apache.giraph.jython.factories.JythonComputationFactory;

 import org.apache.hadoop.conf.Configuration;

 import org.python.core.Py;

 import org.python.core.PyObject;

 import org.python.util.PythonInterpreter;

 import static org.apache.giraph.conf.GiraphConstants.COMPUTATION_FACTORY_CLASS;

 import static org.apache.giraph.conf.GiraphConstants.COMPUTATION_LANGUAGE;

 /**

  * Helpers for running jobs with Jython.

  */

 public class JythonUtils {

   /**

    * The Jython interpreter. Cached here for fast access. We use a singleton

    * for this so that we can parse all of the Jython scripts once at startup

    * and then have their data loaded for the rest of the job.

    */

   private static final PythonInterpreter INTERPRETER =

       new PythonInterpreter();

   /** Don't construct */

   private JythonUtils() { }

   /**

    * Get Jython interpreter

    *

    * @return interpreter

    */

   public static PythonInterpreter getInterpreter() {

     return INTERPRETER;

   }

   /**

    * Sets up the Configuration for using Jython

    *

    * @param conf Configuration to se

    * @param klassName Class name of Jython Computation

    */

   public static void init(Configuration conf, String klassName) {

     COMPUTATION_LANGUAGE.set(conf, Language.JYTHON);

     COMPUTATION_FACTORY_CLASS.set(conf, JythonComputationFactory.class);

     JythonOptions.JYTHON_COMPUTATION_CLASS_NAME.set(conf, klassName);

   }

   /**

    * Instantiate new instance of the Jython class

    *

    * @param className Jython class name

    * @return new instance of class

    */

   public static PyObject newInstance(String className) {

     PyObject pyClass = JythonUtils.getInterpreter().get(className);

     PyObject pyObject = pyClass.__call__();

     return pyObject;

   }

   /**

    * Instantiate new instance of the Jython class

    *

    * @param <T> Jython type

    * @param className Jython class name

    * @param klass Java interface Class

    * @return new instance of class

    */

   public static <T> T newInstance(String className, Class<? extends T> klass) {

     PyObject pyObject = newInstance(className);

     Object object = pyObject.__tojava__(klass);

     if (Py.NoConversion.equals(object)) {

       throw new IllegalArgumentException("Cannot coerce Jython class " +

           className + " to Java type " + klass.getSimpleName());

     } else {

       return (T) object;

     }

   }

 }