Abstract Time Singleton.as

public class Time {
	import flash.utils.getQualifiedClassName;
	public static const TIME_IS_INTRINSIC:int = 0;
	public static const TIME_IS_EXTRINSIC:int = 1;

	private static const CLASSNAME:String = getQualifiedClassName(new Time());

	protected var paused:Boolean;
	protected var lastTime:uint;
	protected var accumulated:uint;

	public function Time():void {
		if (getQualifiedClassName(this) == CLASSNAME) throw new Error("Not allowed to instaniate abstract " + CLASSNAME + " object.");
	}

	public function get now():uint {
		if (!paused) lastTime = getTimer() - accumulated;
		else accumulated = getTimer() - lastTime;
		return lastTime;
	}

	public function pause():void { paused = true; }

	public function resume(timeMult:int):void {
		throw new Error("Method \"resume\" must be defined by child classes.");
	}

	public function get tick():ISignal;
}