enum CourseSource { school, file, demo }

class Course {
  Course({
    required this.id,
    required this.name,
    required this.teacher,
    required this.room,
    required this.weekday,
    required this.startPeriod,
    required this.endPeriod,
    required Set<int> weeks,
    required this.source,
  }) : weeks = Set.unmodifiable(weeks) {
    if ([id, name, teacher, room].any((value) => value.trim().isEmpty) ||
        weekday < 1 ||
        weekday > 7 ||
        startPeriod < 1 ||
        endPeriod > 11 ||
        endPeriod < startPeriod ||
        weeks.isEmpty ||
        weeks.any((week) => week < 1 || week > 30)) {
      throw ArgumentError('课程字段、节次或周次无效');
    }
  }
  final String id, name, teacher, room;
  final int weekday, startPeriod, endPeriod;
  final Set<int> weeks;
  final CourseSource source;
}