export type TimeListener = (time:number)=>void;

export class Timer {

    private timeMs = 0;
    private speed = 1;
    private timerInterval = 1000;
    private direction: 'forward' | 'backward' = 'forward';

    private interval: NodeJS.Timeout = null;

    private listeners:TimeListener[] = [];

    constructor(speed:number = 1,intervalMs:number = 1000) {
        this.speed = speed;
        this.timerInterval = intervalMs;
    }

    start() {
        if(this.interval)
            clearInterval(this.interval);

        this.interval = setInterval(this.intervalCallback.bind(this),this.timerInterval/this.speed);
    }

    stop() {
        clearInterval(this.interval);
        this.timeMs = 0;
        this.interval = null;
        this.listeners.forEach(l => l(0));
    }

    pause() {
        clearInterval(this.interval);
        this.interval = null;
    }

    addListener(l:TimeListener) {
        this.listeners.push(l);
    }

    clearListeners() {
        this.listeners = [];
    }

    get Time() : number {
        return this.timeMs;
    }

    set Time(t:number){
        this.timeMs = t;
        if(this.interval)
            this.start();
    }

    get Speed() : number {
        return this.speed;
    }

    set Speed(s:number) {
        this.speed = s;
        if(this.interval)
            this.start();
    }

    get isRunning() : boolean {
        return Boolean(this.interval);
    }

    set Direction(d:'forward' | 'backward') {
        this.direction = d;
    }

    private intervalCallback() {
        this.timeMs += (this.direction === 'forward' ? 1 : -1) * this.timerInterval;
        this.listeners.forEach(l => l(this.timeMs));
    }
}