from .time_countdown_types import Countdown


def _whole(value: object) -> bool:
    # bool is an int in Python; True is not a number of seconds.
    return isinstance(value, int) and not isinstance(value, bool)


def countdown(until: int, now: int) -> Countdown:
    """The time left until `until`, as a number and as a timer's text. A
    moment is reached at `until` itself, as a JWT's exp is (RFC 7519 4.1.4),
    so now == until is expired with nothing left."""
    if not _whole(until):
        raise ValueError("until must be a whole number of seconds")
    if not _whole(now):
        raise ValueError("now must be a whole number of seconds")
    seconds = until - now if until > now else 0
    h, rest = divmod(seconds, 3600)
    m, s = divmod(rest, 60)
    text = "%d:%02d:%02d" % (h, m, s) if h > 0 else "%d:%02d" % (m, s)
    return Countdown(expired=seconds == 0, seconds=seconds, text=text)