rxjs reset scan stream and pause/ start

scan-reset-pause.ts

import { BehaviorSubject, Observable } from 'rxjs';
import {
  combineLatest, filter, map, scan, tap,
} from 'rxjs/operators';

const scanResetPause = ($isBusy: Observable<boolean>) => {
    return interval(2000).pipe(
      scan((acc, value) => {
        if (!isBusy$.getValue()) {
          return { prevIsBusy: false, value };
        }

        if (!acc.prevIsBusy) {
          return { prevIsBusy: true, value };
        }

        return { prevIsBusy: true, value: acc.value + value };
      }, ({ prevIsBusy: false, value: 0 })),
      combineLatest(isBusy$),
      filter(([, isBusy]) => !isBusy),
      map(([{ value }]) => value),
      tap(c => console.warn(c, 'result')),
    );
    }
}

let busy = false;
const isBusy$ = new BehaviorSubject(busy);

setInterval(() => {
  busy = !busy;
  isBusy$.next(busy);
}, 5000);

scanResetPause(isBusy$).subscribe(console.warn);