class MonthStart {
  final DateTime month;           // YYYY-MM-01
  final int startMinutes;         // starthours (in Minuten)
  final int startVacationUnits;   // startvacation (z.B. Tage)
  final int overtimeMinutes;      // overtime (Minuten)
  final int correctionMinutes;    // correction (Minuten)

  const MonthStart({
    required this.month,
    required this.startMinutes,
    required this.startVacationUnits,
    required this.overtimeMinutes,
    required this.correctionMinutes,
  });

  /// Basis für kumulierte Differenz
  int get carryBaseMinutes => startMinutes + overtimeMinutes + correctionMinutes;

  static MonthStart fromJson(Map<String, dynamic> json) {
    final bookings = (json['bookings'] as List?) ?? const [];
    final row = bookings.isNotEmpty ? (bookings.first as Map<String, dynamic>) : const <String, dynamic>{};
    final dateStr = (json['date'] as String?) ?? '1970-01-01';
    final dt = DateTime.tryParse(dateStr) ?? DateTime(1970, 1, 1);

    int _toInt(dynamic v) => v is num ? v.toInt() : int.tryParse('$v') ?? 0;

    return MonthStart(
      month: DateTime(dt.year, dt.month, 1),
      startMinutes: _toInt(row['starthours']),
      startVacationUnits: _toInt(row['startvacation']),
      overtimeMinutes: _toInt(row['overtime']),
      correctionMinutes: _toInt(row['correction']),
    );
  }
}