// lib/utils/holidays_at.dart
import 'helpers.dart'; // ymd(DateTime)

DateTime _easterSunday(int year) {
  final a = year % 19;
  final b = year ~/ 100;
  final c = year % 100;
  final d = b ~/ 4;
  final e = b % 4;
  final f = ((b + 8) ~/ 25);
  final g = ((b - f + 1) ~/ 3);
  final h = (19 * a + b - d - g + 15) % 30;
  final i = c ~/ 4;
  final k = c % 4;
  final l = (32 + 2 * e + 2 * i - h - k) % 7;
  final m = ((a + 11 * h + 22 * l) ~/ 451);
  final month = ((h + l - 7 * m + 114) ~/ 31);
  final day = ((h + l - 7 * m + 114) % 31) + 1;
  return DateTime(year, month, day);
}

DateTime _addDays(DateTime d, int days) => DateTime(d.year, d.month, d.day + days);

Map<String, String> buildHolidayMapAT(
  int year, {
  bool includeWeekends = false,
}) {
  final Map<String, String> map = {};

  // setzt nur, wenn noch nichts gesetzt wurde (echte Feiertage sollen Vorrang haben)
  void putIfEmpty(DateTime date, String name) {
    final key = ymd(date);
    map.putIfAbsent(key, () => name);
  }

  // Bewegliche Feiertage
  final easter = _easterSunday(year);
  // (Karfreitag ist in AT nicht generell arbeitsfrei – ggf. entfernen)
  putIfEmpty(_addDays(easter, -2), 'Karfreitag');
  putIfEmpty(_addDays(easter, 1), 'Ostermontag');
  putIfEmpty(_addDays(easter, 39), 'Christi Himmelfahrt');
  putIfEmpty(_addDays(easter, 50), 'Pfingstmontag');
  putIfEmpty(_addDays(easter, 60), 'Fronleichnam');

  // Feste Feiertage
  putIfEmpty(DateTime(year, 1, 1), 'Neujahr');
  putIfEmpty(DateTime(year, 1, 6), 'Heilige Drei Könige');
  putIfEmpty(DateTime(year, 5, 1), 'Staatsfeiertag');
  putIfEmpty(DateTime(year, 8, 15), 'Mariä Himmelfahrt');
  putIfEmpty(DateTime(year, 10, 26), 'Nationalfeiertag');
  putIfEmpty(DateTime(year, 11, 1), 'Allerheiligen');
  putIfEmpty(DateTime(year, 12, 8), 'Mariä Empfängnis');
  putIfEmpty(DateTime(year, 12, 25), 'Christtag');
  putIfEmpty(DateTime(year, 12, 26), 'Stefanitag');

  // Optional: Wochenenden **nur ergänzen**, aber niemals Feiertage überschreiben
  if (includeWeekends) {
    DateTime d = DateTime(year, 1, 1);
    while (d.year == year) {
      final wd = d.weekday;
      if (wd == DateTime.saturday || wd == DateTime.sunday) {
        final key = ymd(d);
        if (!map.containsKey(key)) {
          putIfEmpty(d, wd == DateTime.saturday ? 'Samstag' : 'Sonntag');
        }
      }
      d = d.add(const Duration(days: 1));
    }
  }

  return map;
}