import 'app_settings.dart';
import 'course.dart';
import 'semester.dart';

class ImportMetadata {
  const ImportMetadata({
    required this.source,
    required this.importedAt,
    required this.parserVersion,
  });
  final CourseSource source;
  final DateTime importedAt;
  final String parserVersion;
}

class AppSnapshot {
  AppSnapshot({
    this.settings = const AppSettings(),
    List<Course> courses = const [],
    this.importMetadata,
    Map<String, String> calendarEventIds = const {},
  }) : courses = List.unmodifiable(courses),
       calendarEventIds = Map.unmodifiable(calendarEventIds);
  final AppSettings settings;
  final List<Course> courses;
  final ImportMetadata? importMetadata;
  final Map<String, String> calendarEventIds;
  AppSnapshot copyWith({
    AppSettings? settings,
    List<Course>? courses,
    ImportMetadata? importMetadata,
    Map<String, String>? calendarEventIds,
    bool clearMetadata = false,
  }) => AppSnapshot(
    settings: settings ?? this.settings,
    courses: courses ?? this.courses,
    importMetadata: clearMetadata
        ? null
        : importMetadata ?? this.importMetadata,
    calendarEventIds: calendarEventIds ?? this.calendarEventIds,
  );
  Map<String, dynamic> toJson() => {
    'schemaVersion': 1,
    'courses': courses.map((c) => c.toJson()).toList(),
    'settings': {
      'semester': settings.semester == null
          ? null
          : {
              'startDate': settings.semester!.startDate
                  .toIso8601String()
                  .substring(0, 10),
              'totalWeeks': settings.semester!.totalWeeks,
            },
      'remindersEnabled': settings.remindersEnabled,
      'reminderMinutes': settings.reminderMinutes,
      'colorMode': settings.colorMode.name,
      'singleColorArgb': settings.singleColorArgb,
      'calendarEnabled': settings.calendarEnabled,
      'calendarId': settings.calendarId,
    },
    'importMetadata': importMetadata == null
        ? null
        : {
            'source': importMetadata!.source.name,
            'importedAt': importMetadata!.importedAt.toUtc().toIso8601String(),
            'parserVersion': importMetadata!.parserVersion,
          },
    'calendarEventIds': calendarEventIds,
  };
  static AppSnapshot fromJson(Map<String, dynamic> json) {
    try {
      if (json['schemaVersion'] != 1) throw const FormatException('不支持的保存版本');
      final values = (json['courses'] as List)
          .map((c) => Course.fromJson(Map<String, dynamic>.from(c as Map)))
          .toList();
      if (values.map((c) => c.id).toSet().length != values.length ||
          values.any((c) => c.source == CourseSource.demo)) {
        throw const FormatException('保存课表无效');
      }
      final s = Map<String, dynamic>.from(json['settings'] as Map);
      final minutes = s['reminderMinutes'] as int;
      if (![5, 10, 15, 30, 60].contains(minutes)) {
        throw const FormatException('提醒时间无效');
      }
      final color = s['singleColorArgb'] as int;
      if (color < 0 || color > 0xFFFFFFFF) throw const FormatException('颜色无效');
      final sem = s['semester'];
      final term = sem == null
          ? null
          : Semester(
              startDate: DateTime.parse(sem['startDate'] as String),
              totalWeeks: sem['totalWeeks'] as int,
            );
      final metadata = json['importMetadata'];
      return AppSnapshot(
        courses: values,
        settings: AppSettings(
          semester: term,
          remindersEnabled: s['remindersEnabled'] as bool,
          reminderMinutes: minutes,
          colorMode: ColorMode.values.byName(s['colorMode'] as String),
          singleColorArgb: color,
          calendarEnabled: s['calendarEnabled'] as bool,
          calendarId: s['calendarId'] as String?,
        ),
        importMetadata: metadata == null
            ? null
            : ImportMetadata(
                source: CourseSource.values.byName(
                  metadata['source'] as String,
                ),
                importedAt: DateTime.parse(metadata['importedAt'] as String),
                parserVersion: metadata['parserVersion'] as String,
              ),
        calendarEventIds: (json['calendarEventIds'] as Map).map(
          (k, v) => MapEntry(k as String, v as String),
        ),
      );
    } catch (_) {
      throw const FormatException('保存文件内容无效，未覆盖已有数据');
    }
  }
}