source: other-projects/FileTransfer-WebSocketPair/GWTTomcatSocketServer/src/ActionResponseHandler.java@ 31449

import java.util.LinkedList;

import org.nbk4.gwt.action.client.ActionRequest;


public abstract class ActionResponseHandler {
    //there may be some sort of concurrency issue to deal with - we'll figure that out later
    private static Object monitor = new Object();
    private static LinkedList<ActionResponseHandler> registeredHandlers = new LinkedList<ActionResponseHandler>();
    
    private static long getRelativeTimeOutDate(long timeOut) {
        if(timeOut <= 0) {
            return 0;
        }
        else {
            return (System.currentTimeMillis() / 1000L) + timeOut;
        }
    }
    
    public static void addHandler(ActionResponseHandler handler) {
        synchronized(monitor) {
            registeredHandlers.add(handler);
        }
    }
    
    public static boolean handleIfResponse(ActionRequest request) {
        LinkedList<ActionResponseHandler> opt_filter = new LinkedList<ActionResponseHandler>();
        
        //don't want any changes to the object as we use it
        synchronized(monitor) {
            boolean done = false;
            for (ActionResponseHandler handler : registeredHandlers) {
                if(handler.isTimedOut()) {
                    //we've handled this event - nothing else to do here
                }               
                else if (!done && handler.tryToHandle(request)) {
                    done = true;
                }
                else {
                    opt_filter.add(handler);
                }
            }
            registeredHandlers = opt_filter;
        }
        //no matching event handler found
        return false;
    }
    
    /*FIELDS*/
    private long timeOutDate = 0;
    
    /*FUNCTIONS*/
    //timeOut in seconds: use zero, or anything less than 0, for no timeout
    //If a response is received, then any non-answering call past the timeout will be destructed!
    protected ActionResponseHandler(long timeOut) {
        timeOutDate = getRelativeTimeOutDate(timeOut);
    }
    
    /**
     *tryToHandle: should have presupplied a target to handle.
     *When getting the request, handle it as you decide. Return true to mark that it was
     *handled, which allows the managing class to destroy this handler.
     */ 
    public abstract boolean tryToHandle(ActionRequest request);
    
    //Implementation of this entirely up to end user? Who knows. Set a timeout, destroy self on timeout>?
    
    //TODO: convert to milliseconds, change parameter to indicate milliseconds
    public boolean isTimedOut() {
        if (timeOutDate != 0 && System.currentTimeMillis() / 1000L >= timeOutDate) {
            //TODO: Logger
            System.err.println("DEBUG: Handler has timed out: ");
            return true;
        }
        return false;
    }
}