package uu.mal.skate.threading;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public abstract class PausableScheduledTask {

	public abstract void task();

	public abstract long getInitialDelay();

	public abstract long getPeriodDelay();

	public abstract TimeUnit getTimeUnit();

	private ScheduledExecutorService executor = null;
	private volatile boolean isPaused = false;

	Runnable scheduler = new Runnable() {
		@Override
		public void run() {
			if (!isPaused)
				task();
		}
	};

	public void start() {
		if (executor == null || executor.isShutdown()) {
			executor = Executors.newSingleThreadScheduledExecutor();
			executor.scheduleAtFixedRate(scheduler, getInitialDelay(), getPeriodDelay(), getTimeUnit());
		} else {
			resume();
		}
	}

	public void pause() {
		isPaused = true;
	}

	public void resume() {
		isPaused = false;
	}

	public void stop() {
		if(executor != null) {
			executor.shutdownNow();
			executor = null;
		}
	}

}