RxJS timer() replacement for values more than 24 days in the future

long-timer.ts

// compare https://github.com/ReactiveX/rxjs/issues/3015

import { concat, last, Observable, repeat, scan, SchedulerLike, take, timer } from 'rxjs';
import { map } from 'rxjs/operators';

const MAX_INT = 2147483647;

const getTimer = (time: number, scheduler: SchedulerLike | undefined): Observable<0> => {
  if (time > MAX_INT) {
    const n: number = Math.floor(time / MAX_INT);
    const r: number = time % MAX_INT;
    return concat(timer(MAX_INT, MAX_INT, scheduler).pipe(take(n)), timer(r, scheduler)).pipe(
      last(),
      map(() => 0)
    );
  }

  return timer(time, scheduler);
};

const isInterval = (interval: SchedulerLike | number | undefined): interval is number => typeof interval === 'number';

export const longTimer = (
  time: number | Date,
  interval?: SchedulerLike | number,
  scheduler?: SchedulerLike
): Observable<number> => {
  if (time instanceof Date) {
    time = time.getTime() - new Date().getTime();
  }

  if (!isInterval(interval)) {
    return getTimer(time, interval);
  }

  return concat(
    getTimer(time, scheduler),
    getTimer(interval, scheduler).pipe(
      repeat(),
      scan((acc) => acc + 1, 0)
    )
  );
};