package fi.etie.ifms.jbpm;

import javax.servlet.ServletException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.PlugIn;
import org.apache.struts.config.ModuleConfig;
import org.jbpm.JbpmConfiguration;
import org.jbpm.impl.ServiceFactory;
import org.jbpm.scheduler.SchedulerServer;

/**
 * A Struts Plug-In to poll the JBPM Scheduler. On init, it starts a thread that
 * will repeatedly sleep, poll the scheduler and execute scheduled jobs, until
 * destroy method is invoked.
 *
 * @author Diego Ballve /
 *         <a href="http://www.digital-artefacts.fi/">Digital Artefacts Europe</a>
 */
public class SchedulerPlugIn implements PlugIn {

    /** The log */
    private static final Log log = LogFactory.getLog(SchedulerPlugIn.class);

    /** The trigger worker thread */
    private Thread triggerThread;
    /** Flag to signal plug-in status and control worker thread */
    private boolean active = false;
            
    public void destroy() {
        active = false;
        triggerThread.interrupt();
    }
    
    public void init(ActionServlet actionServlet, ModuleConfig moduleConfig)
    throws ServletException {
        active = true;
        triggerThread = new Thread(new SchedulerTrigger());
        triggerThread.start();
    }
    
    /** Worker class (Runnable) */
    class SchedulerTrigger implements Runnable {
        public ServiceFactory serviceFactory;

        public void run() {
            // start the polling server after 5 minutes (let the server boot)
            // after that use time to wait returned from checkJobs.
            long millisToWait = 300000;
            
            while(active) {
                sleep(millisToWait);
                if (!active) break;
                try {
                    log.debug("triggering the server to execute jobs");
                    serviceFactory = JbpmConfiguration.getInstance().getServiceFactory();
                    SchedulerServer schedulerServer = serviceFactory.openSchedulerServer();
                    millisToWait = schedulerServer.checkJobs();
                    schedulerServer.close();
                } catch (Exception e) {
                    log.error("Exception on triggering poll scheduler", e);
                }
            }
        }
        
        private void sleep(long millisToWait) {
            try {
                log.debug("waiting for " + millisToWait + " milliseconds");
                Thread.sleep( millisToWait );
            } catch (InterruptedException e) {
                log.warn("Thread sleeping interrupted", e);
            }
        }
    }
}