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package com.hfg.util.scheduler;

import java.util.Date;
import java.util.logging.Level;
import java.util.logging.Logger;

import com.hfg.util.StringUtil;

//------------------------------------------------------------------------------
/**
 Runs specified job on a specified schedule.
 
 @author J. Alex Taylor, hairyfatguy.com
 
 */
//------------------------------------------------------------------------------
// com.hfg Library
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// J. Alex Taylor, President, Founder, CEO, COO, CFO, OOPS hairyfatguy.com
// [email protected]
//------------------------------------------------------------------------------

public class ScheduledJob implements Runnable
{
   private String   mName;
   private Runnable mJob;
   private Schedule mSchedule;
   private Thread   mThread;
   private boolean  mIsActive = true; // Should this job still be managed by the Scheduler
   private boolean  mIsPaused = false;
   private boolean  mIsCurrentlyExecuting = false;
   private boolean  mExecuteNow = false;
   private Date     mLastExecutionStartDate;

   private final static Logger LOGGER = Logger.getLogger(Scheduler.class.getPackage().getName());

   //###########################################################################
   // CONSTRUCTORS
   //###########################################################################

   //------------------------------------------------------------------------
   public ScheduledJob(Runnable inJob, Schedule inSchedule)
   {
      mJob      = inJob;
      mSchedule = inSchedule;
   }

   //###########################################################################
   // PUBLIC METHODS
   //###########################################################################

   //------------------------------------------------------------------------
   public ScheduledJob setName(String inValue)
   {
      mName = inValue;
      return this;
   }

   //------------------------------------------------------------------------
   public String name()
   {
      return (StringUtil.isSet(mName) ? mName : mJob.getClass().getSimpleName());
   }

   //------------------------------------------------------------------------
   @Override
   public String toString()
   {
      return name();
   }

   //------------------------------------------------------------------------
   public Runnable getJob()
   {
      return mJob;
   }

   //------------------------------------------------------------------------
   public Schedule getSchedule()
   {
      return mSchedule;
   }

   //------------------------------------------------------------------------
   public Thread getThread()
   {
      return mThread;
   }

   //------------------------------------------------------------------------
   public Date getLastExecutionStartDate()
   {
      return mLastExecutionStartDate;
   }

   //------------------------------------------------------------------------
   public void start()
   {
      if (null == mThread)
      {
         mThread = new Thread(this);
         mThread.setName(name());
         mThread.start();
      }

      mIsActive = true;
   }

   //------------------------------------------------------------------------
   public void stop()
   {
      mIsActive = false;
      mThread.interrupt();
   }

   //------------------------------------------------------------------------
   public void pause()
   {
      mIsPaused = true;
   }

   //------------------------------------------------------------------------
   public void resume()
   {
      mIsPaused = false;
   }

   //------------------------------------------------------------------------
   public void executeNow()
   {
      if (! mIsCurrentlyExecuting)
      {
         mExecuteNow = true;
         mThread.interrupt();
      }
   }

   //------------------------------------------------------------------------
   public void run()
   {
      while (mIsActive)
      {
         try
         {
            Date nextScheduledExecutionTime = mSchedule.next();
            if (nextScheduledExecutionTime != null)
            {
               if (! mExecuteNow)
               {
                  LOGGER.log(Level.FINE, "Next scheduled execution time: " + nextScheduledExecutionTime);

                  // Just sleep until it is time to execute this job again
                  Thread.sleep(nextScheduledExecutionTime.getTime() - System.currentTimeMillis());

               }

               if (mIsPaused
                     && ! mExecuteNow)
               {
                  LOGGER.log(Level.FINE, "Skipping this execution instance since this job is currently paused.");
               }
               else
               {
                  mExecuteNow = false;
                  mIsCurrentlyExecuting = true;
                  mLastExecutionStartDate = new Date();

                  mJob.run();
               }
            }
         }
         catch (InterruptedException e)
         {
            // Ignore
         }
         catch (Throwable e2)
         {
            e2.printStackTrace();
            //TODO: Have the scheduler log the exception
         }
      }

      LOGGER.log(Level.INFO, "Scheduled job " + mJob.getClass().getSimpleName() + " is exiting and will no longer be run.");
   }

}