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package com.sun.grizzly.comet;

import java.io.IOException;

/**
 * This interface represents a suspended connection (or response). Passing an 
 * instance of this class to {@link CometContext#addCometHandler} automatically
 * tells Grizzly Comet to suspend the underlying connection and to avoid commiting the 
 * response. Since the response is not commited, the connection is considered
 * as suspended and can be resumed later when an event happens by invoking 
 * {@link CometContext#resumeCometHandler(CometHandler)},
 * from {@link CometHandler#onEvent}. 
 * 
 * {@link CometContext#resumeCometHandler(CometHandler),
 * resume the connection by commiting the response. As an example, a browser icons
 * will spins when a connection is suspended, as the complete response hasn't been
 * sent back. 
 * 
 * Components that implement this interface will be notified 
 * {@link CometContext#notify(String)} is invoked or when
 * the {@link CometContext#getExpirationDelay()} expires.
 *
 * With {@link Servlet}, it is recommended to attach the {@link HttpServletResponse}
 * and use this object to push back messages to the client.
 *
 * @author Jeanfrancois Arcand
 */
public interface CometHandler {

    /**
     * Attach an intance of E to this class.
     */
    void attach(E attachment);
    
    
    /**
     * Receive {@link CometEvent} notification. This method will be invoked
     * everytime a {@link CometContext#notify} is invoked. The {@link CometEvent}
     * will contains the message that can be pushed back to the remote client,
     * cached or ignored. This method can also be used to resume a connection
     * once a notified by invoking {@link CometContext#resumeCometHandler}.

     * its not optimal to flush outputstream in this method for long polling,
     * flush is performed in each CometContext.resume call.

     * flushing multiple times can fragment the data into several tcp packets,
     * that leads to extra IO and overhead in general due to client ack for each packet etc.
     */
    void onEvent(CometEvent event) throws IOException;
    
    
    /**
     * Receive {@link CometEvent} notification when Grizzly is about to
     * suspend the connection. This method is always invoked during the 
     * processing of {@link CometContext#addCometHandler} operations.
     */
    void onInitialize(CometEvent event) throws IOException;
    
    
    /**
     * Receive {@link CometEvent} notification when the response
     * is resumed by a {@link CometHandler} or by the {@link CometContext}
     */
    void onTerminate(CometEvent event) throws IOException;
    
    
    /**
     * Receive {@link CometEvent} notification when the underlying 
     * tcp communication is resumed by Grizzly. This happens
     * when the {@link CometContext#setExpirationDelay} expires or when
     * the remote client close the connection.
     */
    void onInterrupt(CometEvent event) throws IOException;
    
}