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

long-delay.ts

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

import { concat, delay, delayWhen, last, MonoTypeOperatorFunction, Observable, SchedulerLike, take, timer } from 'rxjs';

const MAX_INT = 2147483647;

export const longDelay =
  <T>(due: number | Date, scheduler?: SchedulerLike): MonoTypeOperatorFunction<T> =>
  (source: Observable<T>): Observable<T> => {
    if (due <= MAX_INT) {
      return source.pipe(delay(due, scheduler));
    }

    return source.pipe(
      delayWhen(() => {
        if (due instanceof Date) {
          due = due.getTime() - new Date().getTime();
        }

        const n: number = Math.floor(due / MAX_INT);
        const r: number = due % MAX_INT;

        return concat(timer(MAX_INT, MAX_INT, scheduler).pipe(take(n)), timer(r, scheduler)).pipe(last());
      })
    );
  };