import { EventEmitter } from "events";

/** Timer class representing a Timer task. */
export class Timer {
  /** The active state of the Timer. Has to be false to apply changes to the interval and callback function. */
  private _activeState: boolean;
  /** Gets the active state of the Timer. Has to be false to apply changes to the interval and callback function. */
  public get activeState(): boolean {
    return this._activeState;
  }

  /** The intervalId of the Timer. The inner object of the Timer provided by the native setInterval function. */
  private _intervalId: NodeJS.Timer;
  /** Gets the intervalId of the Timer. The inner object of the Timer provided by the native setInterval function. */
  public get intervalId(): NodeJS.Timer {
    return this._intervalId;
  }

  /** The interval in which the Timer should fire the callback function given in ms. */
  private _interval: number;
  /** The interval in which the Timer should fire the callback function given in ms. Can only be set if activeState is false. */
  public get interval(): number {
    return this._interval;
  }
  public set interval(value: number) {
    if (this._activeState === false) {
      this._interval = value;
    }
  }

  /** The callback event which the Timer should fire each interval. */
  private _callbackEvent: EventEmitter = new EventEmitter();
  /** The callback event which the Timer should fire each interval. */
  public get callbackEvent(): EventEmitter {
    return this._callbackEvent;
  }

  /**
   * Create a Timer.
   * @param interval - The interval in which the Timer should fire the callback function given in ms.
   */
  constructor(interval: number) {
    this._interval = interval;
    this._activeState = false;
  }

  /** Starts the Timer if the current activeState is false. */
  public start(): void {
    if (this._activeState === false) {
      this._intervalId = setInterval(() => {
        this.onTick();
      }, this._interval);
      this._activeState = true;
    }
  }

  /** Stops the Timer if the current activeState is true. */
  public stop(): void {
    if (this._activeState) {
      clearInterval(this._intervalId);
      this._intervalId = null;
      this._activeState = false;
    }
  }

  /** Fires the Timer tick manually and emits callback event. */
  public manuallyFireTick(): void {
    this.onTick();
  }

  /** Timer tick, emits the callback event. */
  private onTick(): void {
    this._callbackEvent.emit(null);
  }
}