/**
 * Quiet-hours suppression for partner-action pushes.
 *
 * The Settings UI promises "10 PM – 8 AM, no notifications". The client stores the window in local
 * DataStore AND mirrors it to the recipient's `users/{uid}` doc (quietHoursEnabled / *StartMinutes /
 * *EndMinutes / timezone). Because a partner push carries a `notification` block, the OS shows it
 * directly when the recipient app is backgrounded/killed — so the only place the promise can be kept
 * is server-side, here, before the push is sent (M-001).
 *
 * FAIL-OPEN by design: if quiet hours is not explicitly enabled, or any field (window/timezone) is
 * missing or malformed, we return `false` (do NOT suppress). A bug here can therefore only ever fall
 * back to today's behavior (notification delivered) — it can never wrongly drop a notification, and
 * existing installs keep delivering exactly as before until the client backfills the fields.
 */
export function recipientInQuietHours(
  userData: FirebaseFirestore.DocumentData | undefined,
  now: Date = new Date()
): boolean {
  if (!userData || userData.quietHoursEnabled !== true) return false

  const start = userData.quietHoursStartMinutes
  const end = userData.quietHoursEndMinutes
  const tz = userData.timezone
  if (typeof start !== 'number' || typeof end !== 'number' || typeof tz !== 'string' || !tz) {
    return false
  }

  let nowMinutes: number
  try {
    const parts = new Intl.DateTimeFormat('en-US', {
      timeZone: tz,
      hour: '2-digit',
      minute: '2-digit',
      hour12: false,
    }).formatToParts(now)
    const hour = Number(parts.find((p) => p.type === 'hour')?.value) % 24
    const minute = Number(parts.find((p) => p.type === 'minute')?.value)
    if (Number.isNaN(hour) || Number.isNaN(minute)) return false
    nowMinutes = hour * 60 + minute
  } catch {
    // Unknown/invalid timezone id → fail open.
    return false
  }

  // Window may cross midnight (e.g. 22:00 → 08:00).
  return start <= end
    ? nowMinutes >= start && nowMinutes <= end
    : nowMinutes >= start || nowMinutes <= end
}