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

import 'dart:convert';

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

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');
      }
      return ImportDraft(
        courses: List.unmodifiable(courses),
        explicitlyEmpty: json['explicitlyEmpty'] == true,
        source: source,
        parserVersion: 'json-v1',
      );
    } on FormatException {
      rethrow;
    } catch (_) {
      throw const FormatException('课表文件格式无效');
    }
  }
}