from datetime import UTC, datetime


def humanize_delta(then: datetime, now: datetime | None = None) -> str:
    if now is None:
        now = datetime.now(UTC)
    if then.tzinfo is None:
        then = then.replace(tzinfo=UTC)
    if now.tzinfo is None:
        now = now.replace(tzinfo=UTC)

    seconds = int((now - then).total_seconds())
    if seconds < 0:
        seconds = 0

    if seconds < 45:
        return "just now"
    if seconds < 90:
        return "1 minute ago"
    minutes = seconds // 60
    if minutes < 60:
        return f"{minutes} minutes ago"
    hours = minutes // 60
    if hours < 24:
        return "1 hour ago" if hours == 1 else f"{hours} hours ago"
    days = hours // 24
    if days < 7:
        return "1 day ago" if days == 1 else f"{days} days ago"
    return then.date().isoformat()