import 'app_settings.dart';
import 'course.dart';
import 'semester.dart';
import 'exam_schedule.dart';
import 'school_term.dart';
import 'school_identity.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({
    AppSettings? settings,
    List<Course> courses = const [],
    this.importMetadata,
    this.examSchedule,
    SchoolTerm? schoolTerm,
    this.calendarCleanupPending = false,
    SupportedSchool? selectedSchool,
    Map<String, String> calendarEventIds = const {},
  }) : settings = settings ?? AppSettings(),
       schoolTerm = schoolTerm ?? _legacyTerm(courses, examSchedule),
       selectedSchool =
           selectedSchool ??
           schoolTerm?.school ??
           _legacyTerm(courses, examSchedule)?.school ??
           examSchedule?.school,
       courses = List.unmodifiable(courses),
       calendarEventIds = Map.unmodifiable(calendarEventIds);
  final AppSettings settings;
  final List<Course> courses;
  final ImportMetadata? importMetadata;
  final ExamSchedule? examSchedule;
  final SchoolTerm? schoolTerm;
  final Map<String, String> calendarEventIds;
  final bool calendarCleanupPending;
  final SupportedSchool? selectedSchool;
  static void validateCourseSource(List<Course> courses, SchoolTerm? term) {
    if (term?.school != SupportedSchool.uestcUndergraduate &&
        courses.any((c) => c.endPeriod > 11)) {
      throw const FormatException('第12节需要本科课表来源');
    }
    for (final course in courses) {
      final under = RegExp(r'^uestc-undergraduate-(\d+)-')
          .firstMatch(course.id);
      if (under != null &&
          (term?.school != SupportedSchool.uestcUndergraduate ||
              under[1] != term?.id.toString())) {
        throw const FormatException('本科课程学校或学期不一致');
      }
      if (term?.school == SupportedSchool.uestcUndergraduate &&
          RegExp(r'^uestc-\d+-').hasMatch(course.id)) {
        throw const FormatException('本科课表包含研究生课程标识');
      }
    }
  }

  static SchoolTerm? _legacyTerm(List<Course> courses, ExamSchedule? exams) {
    final ids = courses
        .map(
          (course) => RegExp(r'^uestc-(\d+)-').firstMatch(course.id)?.group(1),
        )
        .whereType<String>()
        .toSet();
    if (exams?.school == SupportedSchool.uestcGraduate) ids.add(exams!.termId);
    if (ids.length != 1) return null;
    final id = int.tryParse(ids.single);
    return id != null && id >= 1 && id <= 9999 ? SchoolTerm(id) : null;
  }

  AppSnapshot copyWith({
    AppSettings? settings,
    List<Course>? courses,
    ImportMetadata? importMetadata,
    Map<String, String>? calendarEventIds,
    bool clearMetadata = false,
    ExamSchedule? examSchedule,
    bool clearExams = false,
    SchoolTerm? schoolTerm,
    bool? calendarCleanupPending,
    SupportedSchool? selectedSchool,
  }) => AppSnapshot(
    settings: settings ?? this.settings,
    courses: courses ?? this.courses,
    importMetadata: clearMetadata
        ? null
        : importMetadata ?? this.importMetadata,
    examSchedule: clearExams ? null : examSchedule ?? this.examSchedule,
    schoolTerm: schoolTerm ?? this.schoolTerm,
    calendarEventIds: calendarEventIds ?? this.calendarEventIds,
    calendarCleanupPending:
        calendarCleanupPending ?? this.calendarCleanupPending,
    selectedSchool: selectedSchool ?? this.selectedSchool,
  );
  Map<String, dynamic> toJson() => {
    'schemaVersion': 1,
    'examSchedule': examSchedule?.toJson(),
    'schoolTerm': schoolTerm?.toJson(),
    'selectedSchoolId': selectedSchool?.id,
    '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,
      'reminderOffsets': settings.reminderOffsets,
      'colorMode': settings.colorMode.name,
      'singleColorArgb': settings.singleColorArgb,
      'calendarEnabled': settings.calendarEnabled,
      'calendarId': settings.calendarId,
      'courseHeightScale': settings.courseHeightScale,
    },
    'importMetadata': importMetadata == null
        ? null
        : {
            'source': importMetadata!.source.name,
            'importedAt': importMetadata!.importedAt.toUtc().toIso8601String(),
            'parserVersion': importMetadata!.parserVersion,
          },
    'calendarEventIds': calendarEventIds,
    'calendarCleanupPending': calendarCleanupPending,
  };
  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 rawOffsets = s.containsKey('reminderOffsets')
          ? s['reminderOffsets']
          : [s['reminderMinutes']];
      if (rawOffsets is! List ||
          rawOffsets.isEmpty ||
          rawOffsets.any(
            (v) => v is! int || !AppSettings.allowedReminderMinutes.contains(v),
          )) {
        throw const FormatException('提醒时间无效');
      }
      final offsets = rawOffsets.cast<int>();
      final color = s['singleColorArgb'] as int;
      if (color < 0 || color > 0xFFFFFFFF) throw const FormatException('颜色无效');
      final rawHeight = s.containsKey('courseHeightScale')
          ? s['courseHeightScale']
          : AppSettings.defaultCourseHeightScale;
      if (rawHeight is! num ||
          !rawHeight.isFinite ||
          rawHeight < AppSettings.minCourseHeightScale ||
          rawHeight > AppSettings.maxCourseHeightScale) {
        throw const FormatException('课程条长度无效');
      }
      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'];
      final snapshot = AppSnapshot(
        selectedSchool: json['selectedSchoolId'] == null
            ? null
            : SupportedSchool.fromId(json['selectedSchoolId'] as String),
        schoolTerm: json['schoolTerm'] == null
            ? null
            : SchoolTerm.fromJson(
                Map<String, dynamic>.from(json['schoolTerm'] as Map),
              ),
        examSchedule: json['examSchedule'] == null
            ? null
            : ExamSchedule.fromJson(
                Map<String, dynamic>.from(json['examSchedule'] as Map),
              ),
        calendarCleanupPending:
            (json['calendarCleanupPending'] ?? false) as bool,
        courses: values,
        settings: AppSettings(
          semester: term,
          remindersEnabled: s['remindersEnabled'] as bool,
          reminderOffsets: offsets,
          colorMode: ColorMode.values.byName(s['colorMode'] as String),
          singleColorArgb: color,
          calendarEnabled: s['calendarEnabled'] as bool,
          calendarId: s['calendarId'] as String?,
          courseHeightScale: rawHeight.toDouble(),
        ),
        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),
        ),
      );
      validateCourseSource(values, snapshot.schoolTerm);
      return snapshot;
    } catch (_) {
      throw const FormatException('保存文件内容无效，未覆盖已有数据');
    }
  }
}