import '../domain/course.dart';
import '../domain/school_term.dart';
import '../domain/school_identity.dart';

import 'dart:convert';

class ImportDraft {
  const ImportDraft({
    required this.courses,
    required this.explicitlyEmpty,
    required this.source,
    required this.parserVersion,
    this.semesterLabel,
    this.schoolTerm,
  });
  final List<Course> courses;
  final bool explicitlyEmpty;
  final CourseSource source;
  final String parserVersion;
  final String? semesterLabel;
  final SchoolTerm? schoolTerm;
}

class JsonScheduleImport {
  static ImportDraft parse(String text) {
    try {
      if (utf8.encode(text).length > 2 * 1024 * 1024) {
        throw const FormatException('文件不能超过 2 MB');
      }
      final json = jsonDecode(text);
      if (json is! Map ||
          json['schemaVersion'] != 1 ||
          json['courses'] is! List ||
          (json['isDemo'] != null && json['isDemo'] is! bool) ||
          (json['explicitlyEmpty'] != null &&
              json['explicitlyEmpty'] is! bool)) {
        throw const FormatException('请选择版本 1 的课表 JSON 文件');
      }
      final source = json['isDemo'] == true
          ? CourseSource.demo
          : CourseSource.file;
      final courses = (json['courses'] as List)
          .map(
            (c) => Course.fromJson(
              Map<String, dynamic>.from(c as Map),
              source: source,
            ),
          )
          .toList();
      if (courses.map((c) => c.id).toSet().length != courses.length) {
        throw const FormatException('课程标识重复');
      }
      final termIds = courses
          .map((c) => RegExp(r'^uestc-(\d+)-').firstMatch(c.id)?.group(1))
          .whereType<String>()
          .toSet();
      final term = json['schoolTerm'] != null
          ? SchoolTerm.fromJson(
              Map<String, dynamic>.from(json['schoolTerm'] as Map),
            )
          : termIds.length == 1
          ? SchoolTerm(int.parse(termIds.single))
          : null;
      if (termIds.length > 1 ||
          (term != null &&
              termIds.any(
                (id) =>
                    id != term.id.toString() ||
                    term.school != SupportedSchool.uestcGraduate,
              ))) {
        throw const FormatException('文件中包含不同学期的课程');
      }
      final undergraduateIds = courses
          .map(
            (c) =>
                RegExp(r'^uestc-undergraduate-(\d+)-')
                    .firstMatch(c.id)
                    ?.group(1),
          )
          .whereType<String>()
          .toSet();
      if (undergraduateIds.isNotEmpty &&
              (term?.school != SupportedSchool.uestcUndergraduate ||
                  undergraduateIds.any((id) => id != term!.id.toString())) ||
          courses.any((c) => c.endPeriod > 11) &&
              (source == CourseSource.demo ||
                  term?.school != SupportedSchool.uestcUndergraduate)) {
        throw const FormatException('本科课表来源或学期无效');
      }
      return ImportDraft(
        courses: List.unmodifiable(courses),
        explicitlyEmpty: json['explicitlyEmpty'] == true,
        source: source,
        parserVersion: 'json-v1',
        schoolTerm: source == CourseSource.demo ? null : term,
        semesterLabel: term?.label,
      );
    } on FormatException {
      rethrow;
    } catch (_) {
      throw const FormatException('课表文件格式无效');
    }
  }
}