/*
    * The Kuali Financial System, a comprehensive financial management system for higher education.
    * 
    * Copyright 2005-2014 The Kuali Foundation
    * 
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Affero General Public License as
    * published by the Free Software Foundation, either version 3 of the
    * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU Affero General Public License for more details.
   * 
   * You should have received a copy of the GNU Affero General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  package org.kuali.kfs.sys.context;
  
  import java.util.concurrent.Executor;
  import java.util.concurrent.Executors;
  
  /**
   * This class should be used in the development environment to run the batch container, execute one or more steps, then shut down the batch container.
   */
  public class BatchStepLauncher implements Runnable {
      private static final String LOG_PREFIX = BatchStepLauncher.class.getName() +": ";
      private static final String batchContainerStep = "batchContainerStep";
  
      private static BatchStepTriggerParameters batchStepTriggerParms;
  
      /**
       * This class validates the arguments, adds a shutdown hook to Runtime to clean up BatchContainer's semaphore, starts the batch container,
       * and executes steps using the BatchStepTrigger.
       *
       * The BatchStepTrigger will exit the system using calls to System.exit(). This will cause this Launcher class to exit immediately without executing any further
       * methods. Therefore the batch container cannot be shut down using the iu.stopBatchContainerStep which nicely cleans up its own semaphore. The shutdown hook has been
       * added in order for this cleanup to occur.
       *
       * @param args the String[] arguments normally passed to BatchStepTrigger
       */
      public static void main(String[] args) {
  
          //check arguments for the trigger
          checkArguments(args);
  
          //run the Batch Container in its own thread
          startBatchContainer();
  
          //confirm that the container started up before executing the steps
          //-uses batch container directory specified in args
          confirmStartUp();
  
          //execute one or more steps
          executeSteps(args);
  
          //the batch container will be shut down by the thread hook added to the Runtime in setUp()
      }
  
      /**
       * Run the Batch Container in its own thread
       */
      @Override
      public void run() {
          String[] args = new String[2];
          args[0] = batchContainerStep;
          args[1] = (batchStepTriggerParms != null ? batchStepTriggerParms.getJobName(): "unknown");
  
          BatchStepRunner.main(args);
      }
  
      /**
       * Uses the BatchStepTriggerParameters class to validate the arguments passed to the launcher.
       *
       * @param args String[] of arguments that would normally passed to BatchStepTrigger
       */
      private static void checkArguments(String[] args) {
          logToOut("checking arguments");
  
          batchStepTriggerParms = new BatchStepTriggerParameters(args);
  
          logToOut("received valid arguments");
      }
  
      /**
       * Start the batch container in its own Thread
       */
      private static void startBatchContainer() {
          logToOut("starting the batch container");
          Executor executor = Executors.newCachedThreadPool();
  
          BatchStepLauncher batchStepLauncher = new BatchStepLauncher();
          executor.execute(batchStepLauncher);
      }
  
      /**
       * Loops and polls for the batch container start up (looks for the .runlock)
       */
     private static void confirmStartUp() {
         logToOut("confirming batch container start up");
 
         while (!batchStepTriggerParms.getBatchContainerDirectory().isBatchContainerRunning()) {
             logToOut("waiting for the batch container to start up");
             try {
                 Thread.sleep(batchStepTriggerParms.getSleepInterval());
             }
             catch (InterruptedException e) {
                 throw new RuntimeException("BatchStepLauncher encountered interrupt exception while trying to wait for the batch container to start up", e);
             }
         }
 
         logToOut("batch container is running");
     }
 
     /**
      * Calls BatchStepTrigger to execute steps
      *
      * @param args String[] arguments normally passed to the BatchStepTrigger
      */
     private static void executeSteps(String[] args) {
         logToOut("executing step(s)");
 
         BatchStepTrigger.main(args);
 
         logToOut("finished executing step(s)");
     }
 
     /**
      * Removes the batch container semaphore (used by the shutdown hook added to Runtime)
      * This is necessary because the Launcher exits immediately when the Trigger exits. Shutdown hook cleans up the semaphore.
      */
     private static void removeBatchContainerSemaphore() {
         logToOut("removing batch container semaphore file");
 
         if (batchStepTriggerParms.getBatchContainerDirectory().isBatchContainerRunning()) {
             batchStepTriggerParms.getBatchContainerDirectory().removeBatchContainerSemaphore();
         }
 
         logToOut("batch container semaphore file has been removed");
     }
 
     /**
      * Logs statement to System.out with a prefix.
      *
      * @param statement the statement to log
      */
     private static void logToOut(String statement) {
         System.out.println(LOG_PREFIX + statement);
     }
 }