import javax.swing.SwingUtilities;

/**
 * This class implements a thread to control running
 * of a SaM Program and report back when it is done.
 * This is an easy way of creating a SaM simulator frontend
 * that needs to run a whole program.
 */
public class RunThread extends Thread {
	/**
	 * Provides access to the processor
	 */
	protected Processor proc;
	
	/**
	 * Provides access to the system
	 */
	protected Sys sys;

	/**
	 * The parent of this thread
	 */
	protected ThreadedFrontend parent;

	/**
	 * The delay after each intruction
	 */
	protected int delay = 50;

	/**
	 * Set when the parent calls stop() in order to stop thread execution at
	 * next cycle
	 */
	protected boolean stop = false;

	/**
	 * Indicates that execution was stopped due to
	 * normal program completion
	 */
	public static final int NORMAL = 0;
	/**
	 * Indicates program was stopped due to an error
	 * in execution
	 */
	public static final int ERROR = 1;
	/**
	 * Indicates that a program was stopped because
	 * it was interrupted by stopExecution()
	 */
	public static final int INTERRUPT = 2;

	/**
	 * Creates a new thread
	 * @param parent the frontend that needs to be updated
	 * @param sys the system to use
	 * @param delay # of milliseconds between command execution
	 */
	public RunThread(ThreadedFrontend parent, Sys sys, int delay) {
		this.parent = parent;
		this.sys = sys;
		this.delay = delay;
		proc = sys.cpu();
	}

	/**
	 * Starts the thread
	 */
	public void run() {
		try {
			while (proc.get(Processor.HALT) == 0) {
				if (stop) {
					syncCompletion(INTERRUPT, null);
					return;
				}
				syncUpdate();
				proc.step();
				Thread.sleep(delay);
			}
		}
		catch (Exception e) {
			syncCompletion(ERROR, e);
			return;
		}
		syncCompletion(NORMAL, null);
	}

	/**
	 *This is necessary to prevent GUI from updating while handling AWT events 
	 * This wraps updateStatus() and runDone() calls, so that they will wait until AWT events complete
	 */
	private void syncUpdate() {
		try {
			SwingUtilities.invokeAndWait(new Runnable() {
				public void run() {
					parent.updateStatus();
				}
			});
		}
		catch (Exception e) {
		}
	}

	/**
	 * Called when the thread has completed in order to sync graphics
	 * @param status The exit status code
	 * @param error The error generated, or null if there is none
	 */
	private void syncCompletion(final int status, final Exception error) {
		try {
			SwingUtilities.invokeAndWait(new Runnable() {
				public void run() {
					parent.runDone(status, error);
				}
			});
		}
		catch (Exception e) {
		}
	}

	/**
	 * Stops execution
	 */
	public void stopExecution() {
		stop = true;
	}
}