const TEHRAN = 'Asia/Tehran';

export type AttendanceKind = 'login' | 'logout' | 'forced_logout';

export function tehranDateKey(date: Date): string {
  const parts = new Intl.DateTimeFormat('en-CA', {
    timeZone: TEHRAN,
    year: 'numeric',
    month: '2-digit',
    day: '2-digit',
  }).format(date);
  return parts;
}

/** ساعت HH:mm امروز به وقت تهران، به صورت لحظهٔ مطلق */
export function tehranCutoff(now: Date, hhmm: string): Date | null {
  const match = /^([01]\d|2[0-3]):([0-5]\d)$/.exec(hhmm.trim());
  if (!match) return null;
  const day = tehranDateKey(now);
  return new Date(`${day}T${match[1]}:${match[2]}:00+03:30`);
}

export function isPastLogoutTime(now: Date, hhmm: string | null | undefined): boolean {
  if (!hhmm) return false;
  const cutoff = tehranCutoff(now, hhmm);
  if (!cutoff) return false;
  return now.getTime() >= cutoff.getTime();
}

export function loggedInAfterCutoff(at: Date, hhmm: string | null | undefined): boolean {
  if (!hhmm) return false;
  const cutoff = tehranCutoff(at, hhmm);
  if (!cutoff) return false;
  return at.getTime() >= cutoff.getTime();
}

export function tehranClock(date: Date): string {
  return new Intl.DateTimeFormat('fa-IR', {
    timeZone: TEHRAN,
    hour: '2-digit',
    minute: '2-digit',
    hourCycle: 'h23',
  }).format(date);
}