import 'dart:convert';

import 'package:html/dom.dart';
import 'package:html/parser.dart' as html;

import '../../../domain/exam_schedule.dart';
import '../../../domain/school_identity.dart';
import '../../../domain/school_term.dart';
import '../../../domain/undergraduate_exam_query.dart';

class UndergraduateExamAdapter {
  static const headers = [
    '课程序号',
    '课程名称',
    '考试日期',
    '考试安排',
    '考试地点',
    '座位号',
    '考试情况',
    '考试类型',
    '其它说明',
  ];
  static ExamSchedule extract(
    String content, {
    SchoolTerm? expectedTerm,
    UndergraduateExamType? expectedType,
  }) {
    try {
      if (utf8.encode(content).length > 2 * 1024 * 1024)
        throw const FormatException('考试页面超过2MB');
      final doc = html.parse(content);
      if (doc.querySelector('input[type="password"]') != null)
        throw const FormatException('请先完成学校登录');
      final form = doc.querySelector('#stdExamTableForm');
      final scope = form ?? doc;
      final termValues = scope
          .querySelectorAll('input[name="semester.id"]')
          .map((e) => e.attributes['value'])
          .whereType<String>()
          .toSet();
      final typeValues = scope
          .querySelectorAll('input[name="examType.id"]')
          .map((e) => e.attributes['value'])
          .whereType<String>()
          .toSet();
      for (final params in scope.querySelectorAll('input[name="params"]')) {
        final query = Uri.splitQueryString(
          (params.attributes['value'] ?? '').replaceFirst(RegExp(r'^&'), ''),
        );
        if (query['semester.id'] != null) termValues.add(query['semester.id']!);
        if (query['examType.id'] != null) typeValues.add(query['examType.id']!);
      }
      // Only a result params assignment is evidence, not calendar initialization.
      for (final script in doc.querySelectorAll('script')) {
        for (final m in RegExp(
          r'''\bvar\s+params\s*=\s*["']([^"']+)["']''',
        ).allMatches(script.text)) {
          final query = Uri.splitQueryString(
            m[1]!.replaceFirst(RegExp(r'^&'), ''),
          );
          if (query['semester.id'] != null)
            termValues.add(query['semester.id']!);
          if (query['examType.id'] != null)
            typeValues.add(query['examType.id']!);
        }
      }
      if (termValues.length != 1 || typeValues.length != 1)
        throw const FormatException('排考结果学期或类型不明确');
      final term = SchoolTerm(
        int.parse(termValues.single),
        school: SupportedSchool.uestcUndergraduate,
      );
      final type = UndergraduateExamType.fromId(int.parse(typeValues.single));
      if (expectedTerm != null && expectedTerm != term ||
          expectedType != null && expectedType != type)
        throw const FormatException('排考结果与所选学期或类型不一致');
      Element? table;
      for (final candidate in doc.querySelectorAll('table')) {
        final cells = candidate
            .querySelector('tr')
            ?.children
            .map((c) => c.text.trim())
            .toList();
        if (cells != null &&
            cells.length == headers.length &&
            List.generate(
              headers.length,
              (i) => cells[i] == headers[i],
            ).every((v) => v)) {
          if (table != null) throw const FormatException('排考结果重复');
          table = candidate;
        }
      }
      if (table == null) throw const FormatException('排考页面尚未加载完整');
      final records = <String, ExamRecord>{};
      final explicitEmpty = RegExp(r'暂无考试|无考试安排|没有考试|暂无记录|没有符合条件的记录|没有数据|无数据')
          .hasMatch(table.text);
      for (final row in table.querySelectorAll('tr').skip(1)) {
        final cells = row.children
            .map((c) => c.text.replaceAll(RegExp(r'\s+'), ' ').trim())
            .toList();
        if (cells.length != 9) {
          if (explicitEmpty && cells.length == 1) continue;
          throw const FormatException('考试记录字段不完整');
        }
        final rowType = _type(cells[7]);
        if (rowType != type.id) throw const FormatException('考试记录类型不一致');
        final record = ExamRecord(
          code: cells[0],
          name: cells[1],
          date: cells[2],
          time: cells[3],
          room: cells[4],
          seat: cells[5],
          status: cells[6],
          examTypeId: rowType,
          notes: cells[8],
        );
        if (record.code.isEmpty || record.name.isEmpty)
          throw const FormatException('考试课程缺失');
        records.putIfAbsent(record.undergraduateKey, () => record);
      }
      if (records.isEmpty && !explicitEmpty)
        throw const FormatException('尚未识别到明确的排考结果');
      return ExamSchedule.fromJson(
        ExamSchedule(
          semesterLabel: term.label,
          termId: '${term.id}',
          records: records.values.toList(),
          school: term.school,
          requestedExamTypes: {type.id},
        ).toJson(),
      );
    } on FormatException {
      rethrow;
    } catch (_) {
      throw const FormatException('本科考试页面内容无效，已有考试保持不变');
    }
  }

  static int _type(String text) {
    if (text.contains('期末')) return 1;
    if (text.contains('期中')) return 2;
    if (text.contains('补') || text.contains('缓')) return 3;
    throw const FormatException('考试记录类型无法识别');
  }

  static ExamSchedule merge(
    UndergraduateExamQuery query,
    List<ExamSchedule> parts,
  ) {
    final expected = query.types.map((t) => t.id).toSet(),
        seen = <int>{},
        records = <String, ExamRecord>{};
    for (final raw in parts) {
      final part = ExamSchedule.fromJson(raw.toJson());
      if (part.school != query.term.school ||
          part.termId != '${query.term.id}' ||
          part.requestedExamTypes.length != 1 ||
          !expected.contains(part.requestedExamTypes.single) ||
          !seen.add(part.requestedExamTypes.single))
        throw const FormatException('考试查询批次不一致');
      for (final record in part.records) {
        records.putIfAbsent(record.undergraduateKey, () => record);
      }
    }
    if (seen.length != expected.length || records.length > 500)
      throw const FormatException('考试未全部读取完成或记录超限');
    return ExamSchedule.fromJson(
      ExamSchedule(
        semesterLabel: query.term.label,
        termId: '${query.term.id}',
        records: records.values.toList(),
        school: query.term.school,
        requestedExamTypes: expected,
      ).toJson(),
    );
  }
}