public class PortalVerification implements Runnable {
    
    private boolean isRunning;
    private boolean hasQueue;
    private Set<RealPortal> portalsToVerify;
    
    @Override
    public static void run() {
        //If already running or no work is necessary, skip
        if (isRunning || !hasQueue) {
            return;
        }
        //Update running and queue state
        hasQueue = false;
        isRunning = true;

        //Store and reset the portals to verify
        Set<RealPortal> portalsToCheck;
        if (portalsToVerify != null) {
          portalsToCheck = new HashSet(portalsToVerify);
          portalsToVerify = null;
        } else {
          portalsToCheck = null;//TODO: Get all portals
        }

        //TODO: Do verification stuff here

        //Update running state when finished
        isRunning = false;
    }

    /**
    * Schedules the verification of the given set of Stargates
    */
    public void scheduleVerification(Set<RealPortal> portals) {
      if (portalsToVerify == null) {
        portalsToVerify = portals;
      } else {
        portalsToVerify.addAll(portals);
      }
      scheduleVerification();
    }
    
    /**
    * Schedules the verification of all Stargates 
    */
    public void scheduleVerification() {
        //Notify run() of additional work
        hasQueue = true;
        //Run immediately if possible
        if (!isRunning) {
            run();
        }
    }

}