const { isValidZAPhone } = require('./whatsapp');

const ALLOWED_NOTIFICATION_PREFERENCES = ['email', 'whatsapp', 'both'];

// WhatsApp/Both requires a valid SA phone number — silently falls back to email otherwise,
// since a user without a usable phone number can never receive WhatsApp notifications anyway.
function resolveNotificationPreference(requested, phoneNumber, fallback) {
  if (requested === undefined) return fallback;
  let pref = ALLOWED_NOTIFICATION_PREFERENCES.includes(requested) ? requested : fallback;
  if ((pref === 'whatsapp' || pref === 'both') && !isValidZAPhone(phoneNumber)) {
    pref = 'email';
  }
  return pref;
}

module.exports = { ALLOWED_NOTIFICATION_PREFERENCES, resolveNotificationPreference };