PerformanceTimer.ts

import {BehaviorSubject, Observable, Subject} from "rxjs";
import {Injectable} from "@angular/core";
import {filter} from "rxjs/operators";

@Injectable()
export class PerformanceTimer {
  private _currentTime$ = new BehaviorSubject<number>(0)
  private timer: number | null = null;
  private timeLimit = 0;
  private unlimit = false;
  private stopped = true;

  public currentTime$() {
    return this._currentTime$.asObservable()
  }

  public finishLimit$ = new Subject<void>()

  public getCurrentTime(): number {
    if (this._currentTime$ === undefined) {
      throw Error('Must be init with init() method')
    }

    return this._currentTime$.value
  }

  init(timeLimit: number, unlimit: boolean = false)  {
    this.unlimit = unlimit
    this.timeLimit = timeLimit
    this._currentTime$.next(0)
  }

  continue = () => {
    if (this._currentTime$ === undefined) {
      throw Error('Must be init with init() method')
    }
    this.loop()
  }

  start = () => {
    if (this._currentTime$ === undefined) {
      throw Error('Must be init with init() method')
    }
    this.stopped = false
    this.loop()
  }

  private loop = () => {
    if (this._currentTime$ === undefined) {
      throw Error('Must be init with init() method')
    }

    if (this.stopped) {
      return
    }

    this.stop();

    let lastTimestamp = performance.now();

    const update = () => {
      const time = performance.now();
      this._currentTime$.next(this._currentTime$.value + (time - lastTimestamp))

      lastTimestamp = time;

      if (this._currentTime$.value >= this.timeLimit ) {
        this.finishLimit$.next()
        this.stop()
        return
      }

      if (this._currentTime$.value < this.timeLimit || this.unlimit) {
        this.timer = requestAnimationFrame(update);
      }
    }

    this.timer = requestAnimationFrame(update);
  };

  stop = () => {
    if (this._currentTime$ === undefined) {
      throw Error('Must be init with init() method')
    }

    this._currentTime$.next(0)
    this.stopped = true

    if (this.timer) {
      cancelAnimationFrame(this.timer);
      this.timer = null;
    }
  }
}