package org.expeditee.core;

/**
 * A Runnable which can be asked to block the calling thread until
 * execution of the given code has completed. Runnable's run() method
 * is used as part of the implementation so user code should be specified
 * by overriding the execute() method instead.
 * 
 * @author cts16
 */
public abstract class BlockingRunnable implements Runnable {

	/** Whether the code has finished executing or not. */
	private boolean _done;
	/** Synchronisation object to prevent race conditions. */
	private Object _lock;
	
	public BlockingRunnable()
	{
		_done = false;
		_lock = new Object();
	}
	
	/** Should be overridden to specify user behaviour. */
	public abstract void execute();
	
	@Override
	public final void run()
	{
		execute();
		
		// Mark as finished and wake any blocked threads
		synchronized (_lock) {
			_done = true;
			_lock.notifyAll();
		}
	}
	
	/** Can be called to block the calling thread until the execute() method returns. */
	public final void blockUntilDone()
	{
		synchronized (_lock) {
			while (!_done) {
				try {
					_lock.wait();
				} catch (InterruptedException e) {
					// Do nothing, just try waiting again
				}
			}
		}
	}
}