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,
    this.courseCode = '',
    this.notes = '',
  }) : weeks = Set.unmodifiable(weeks) {
    if ([id, name, teacher, room].any((value) => value.trim().isEmpty) ||
        weekday < 1 ||
        weekday > 7 ||
        startPeriod < 1 ||
        endPeriod > 12 ||
        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 String courseCode, notes;
  final int weekday, startPeriod, endPeriod;
  final Set<int> weeks;
  final CourseSource source;

  Map<String, dynamic> toJson() => {
    'id': id,
    'name': name,
    'teacher': teacher,
    'room': room,
    'weekday': weekday,
    'startPeriod': startPeriod,
    'endPeriod': endPeriod,
    'weeks': weeks.toList()..sort(),
    'source': source.name,
    'courseCode': courseCode,
    'notes': notes,
  };

  static Course fromJson(Map<String, dynamic> json, {CourseSource? source}) {
    try {
      String text(String key) {
        final v = json[key];
        if (v is! String) throw const FormatException('课程字段缺失');
        return v.trim();
      }

      final rawWeeks = json['weeks'];
      if (rawWeeks is! List || rawWeeks.any((w) => w is! int)) {
        throw const FormatException('周次必须是整数数组');
      }
      return Course(
        id: text('id'),
        name: text('name'),
        teacher: text('teacher'),
        room: text('room'),
        weekday: json['weekday'] as int,
        startPeriod: json['startPeriod'] as int,
        endPeriod: json['endPeriod'] as int,
        weeks: rawWeeks.cast<int>().toSet(),
        source: source ?? CourseSource.values.byName(json['source'] as String),
        courseCode: (json['courseCode'] ?? '') as String,
        notes: (json['notes'] ?? '') as String,
      );
    } catch (_) {
      throw const FormatException('课程字段、节次或周次无效');
    }
  }
}