def waiting_for_file(filepath):
    retry_count = 0
    sleep_time_in_minute = 5
    max_age = 12 * 60 * 60  # 12 hour in seconds

    timeout_hours = 8
    alert_hours = 2
    remaining_hours = timeout_hours - alert_hours

    retry_count_before_alert = alert_hours * 60 / sleep_time_in_minute
    retry_count_before_timeout = timeout_hours * 60 / sleep_time_in_minute

    await_done_files = get_flag_value_nullable('await_done_files') or 'yes'

    if await_done_files:
        while True:
            is_file_new = ensure_file_not_stale(filepath, max_age)
            if is_file_new:
                mtime = os.path.getmtime(filepath)
                mtime_str = datetime.fromtimestamp(
                    mtime).strftime("%Y-%m-%d %H:%M:%S %Z")

                print(f"File '{filepath}' arrived at {mtime_str}")
                send_success_mail(filepath, mtime_str)
                break

            if retry_count == retry_count_before_alert:
                print(f"File '{filepath}' is delayed. Sending alert mail...")
                send_alert_mail(filepath, remaining_hours)

            if retry_count == retry_count_before_timeout:
                print(
                    f"File '{filepath}' is either missing or too old. The script has been waiting for {timeout_hours}. Terminated!")
                sys.exit(1)

            retry_count += 1

            time.sleep(sleep_time_in_minute * 60)