/// ============================================================
/// 【课堂习题 · 翻页 / 子题切换 / 答题卡定位】
///
/// 1:1 迁移 Vue exerciseNavigation.js（createNavigationHandlers）。
///
/// Flutter 端 PageView 使用 NeverScrollableScrollPhysics，所有翻页都由
/// 本控制器经 [ExerciseUiBridge.jumpToPage] 主动触发（对标程序 slideTo），
/// PageView.onPageChanged 只接 [handlePageChange] 做状态同步，不再重复提交。
/// ============================================================
library;

import 'dart:async';

import 'package:flutter/widgets.dart';
import 'package:new_learn/features/conquerPackage/classExercises/controllers/exercise_session.dart';
import 'package:new_learn/features/conquerPackage/classExercises/controllers/exercise_sort.dart' as sort;
import 'package:new_learn/features/conquerPackage/classExercises/controllers/exercise_submit.dart';
import 'package:new_learn/features/conquerPackage/classExercises/models/question_model.dart';

class ExerciseNavigationHandlers {
  ExerciseNavigationHandlers({
    required this.session,
    required this.bridge,
    required this.submit,
    required this.openTimePopup,
    required this.openUploadNotesPopup,
    required this.submitExamPaper,
  });

  final ExerciseSession session;
  final ExerciseUiBridge bridge;

  /// 单题提交控制器（calculateRemainTime / QuestionRenewTimeFn）
  final ExerciseSubmitHandlers submit;

  /// 页面级“最低学习时长”拦截（含 isWrong 判断）
  final bool Function() openTimePopup;

  /// 页面级“上传笔记”拦截（含 isWrong 判断）
  final bool Function() openUploadNotesPopup;

  /// 交卷入口
  final void Function(String type) submitExamPaper;

  bool _isProgrammaticJump = false;
  Timer? _programmaticJumpTimer;

  /// 标记程序跳转（400ms 内忽略手势重复触发）
  void markProgrammaticJump({Duration duration = const Duration(milliseconds: 400)}) {
    _isProgrammaticJump = true;
    _programmaticJumpTimer?.cancel();
    _programmaticJumpTimer = Timer(duration, () {
      _isProgrammaticJump = false;
      _programmaticJumpTimer = null;
    });
  }

  bool get isProgrammaticJump => _isProgrammaticJump;

  // ---------------- 题号计算 ----------------

  sort.SortRange getDisplayQuestionSortRange(int targetIndex) =>
      sort.getDisplayQuestionSortRange(session.questions, targetIndex);

  sort.ResolvedSortTarget resolveTargetByDisplaySort(int targetSort) =>
      sort.resolveTargetByDisplaySort(session.questions, targetSort);

  ExerciseSubmitHandlers get _submit => submit;

  int get totalSortCount {
    if (session.questions.isEmpty) return 0;
    return getDisplayQuestionSortRange(session.questions.length - 1).end;
  }

  int get totalWrongSortCount {
    var maxSort = 0;
    for (final item in session.questions) {
      final end = sort.getWrongQuestionSortRange(item).end;
      if (end > maxSort) maxSort = end;
    }
    return maxSort;
  }

  int _safeActiveSubIndex(QuestionModel item) {
    final subs = item.subQuestions;
    if (subs.isEmpty) return 0;
    final raw = session.activeSubIndexMap[session.currentIndex] ?? 0;
    return raw < 0
        ? 0
        : (raw > subs.length - 1 ? subs.length - 1 : raw);
  }

  /// 当前展示题号（currentSortLabel）
  int get currentSortLabel {
    final item = session.currentQuestion;
    if (item == null) return 0;
    final start = getDisplayQuestionSortRange(session.currentIndex).start;
    if (sort.shouldCountSubQuestions(item)) {
      return start + _safeActiveSubIndex(item);
    }
    return start;
  }

  /// 错题模式当前题号（currentWrongSortLabel）
  int get currentWrongSortLabel {
    final item = session.currentQuestion;
    if (item == null) return 0;
    final start = sort.getWrongQuestionSortRange(item).start;
    if (item.hasChild && item.subQuestions.isNotEmpty) {
      final sub = item.subQuestions[_safeActiveSubIndex(item)];
      return sub.wrongSort ?? start;
    }
    return start;
  }

  /// 进度百分比（percentage，ceil）
  int get percentage {
    if (session.isWrong) {
      final total = totalWrongSortCount;
      if (total == 0) return 0;
      final item = session.currentQuestion;
      if (item == null) return 0;
      final range = sort.getWrongQuestionSortRange(item);
      var current = range.start;
      if (sort.shouldCountSubQuestions(item)) {
        final sub = item.subQuestions[_safeActiveSubIndex(item)];
        current = sub.wrongSort ?? range.start;
      }
      return (current / total * 100).ceil();
    }
    final total = totalSortCount;
    if (total == 0) return 0;
    final item = session.currentQuestion;
    if (item == null) return 0;
    final start = getDisplayQuestionSortRange(session.currentIndex).start;
    var current = start;
    if (sort.shouldCountSubQuestions(item)) {
      current = start + _safeActiveSubIndex(item);
    }
    return (current / total * 100).ceil();
  }

  bool get isPrevDisabled =>
      session.currentIndex == 0 ? !canGoPrevSubQuestion() : false;

  // ---------------- 切页状态同步 ----------------

  /// 大题切页后的状态同步（对标 handlePageChange，不含提交）
  void handlePageChange(int index) {
    final prevIndex = session.currentIndex;
    if (prevIndex != index) {
      // 注册表暂停，不遍历 element 树，动画收尾帧调用也安全；
      // 旧页 isActive 翻转后 didUpdateWidget 也会暂停一次（双保险）
      session.itemRefs[prevIndex]?.currentState?.pauseMedia();
    }
    session.currentIndex = index;
    final q = session.currentQuestion;
    if (q != null) {
      q.startTime = getCurrentISO();
    }

    final pendingSub = session.pendingSubIndexMap[index];
    if (pendingSub != null) {
      session.activeSubIndexMap[index] = pendingSub;
      final pageKey = session.itemRefs[index];
      WidgetsBinding.instance.addPostFrameCallback((_) {
        Future<void>.delayed(const Duration(milliseconds: 500), () {
          pageKey?.currentState?.setActiveSubIndex(pendingSub);
          session.pendingSubIndexMap.remove(index);
        });
      });
    }
    session.countDownKey?.currentState?.reset();
    bridge.notifyListeners();
  }

  bool _hasSubQuestions(QuestionModel? item) =>
      sort.shouldCountSubQuestions(item);

  int _currentActiveSubIndex(QuestionModel item) {
    if (!_hasSubQuestions(item)) return -1;
    final total = item.subQuestions.length;
    final current = session.activeSubIndexMap[session.currentIndex] ?? 0;
    return current < 0
        ? 0
        : (current > total - 1 ? total - 1 : current);
  }

  /// 跨大题切页前提交当前页（对标 submitCurrentQuestionBeforePageSwitch）
  void submitCurrentQuestionBeforePageSwitch() {
    _submit.calculateRemainTime();
    final item = session.currentQuestion;
    if (item == null) return;

    // 填空题单个空：直接提交大题
    if (item.childs.length == 1 && item.questionTypes == 'tiankongti') {
      _submit.questionRenewTimeFn(item, null);
      return;
    }
    // hasOptionChildrenQuestion=false 且图片作答：整题算 1 题
    if (item.isFillblankItemUpload == 1 &&
        !item.hasOptionChildrenQuestion) {
      _submit.questionRenewTimeFn(item, null);
      return;
    }
    // 有小题：提交当前激活子题
    if (_hasSubQuestions(item) || item.childs.isNotEmpty) {
      final data = session.panelKey?.currentState?.getChildData();
      _submit.questionRenewTimeFn(
        data?.data ?? QuestionModel(<String, dynamic>{}),
        item.id,
      );
      return;
    }
    _submit.questionRenewTimeFn(item, null);
  }

  /// 复合题面板子题切换（对标 handleSubQuestionChange）
  void handleSubQuestionChange(int questionIndex, int subIndex) {
    final item = questionIndex >= 0 && questionIndex < session.questions.length
        ? session.questions[questionIndex]
        : null;
    final subs = item == null
        ? const []
        : (item.subQuestions.isNotEmpty
            ? item.mapList('subQuestions')
            : item.mapList('bkTagMetaList'));
    final safe = subs.isEmpty
        ? 0
        : (subIndex < 0 ? 0 : (subIndex > subs.length - 1 ? subs.length - 1 : subIndex));
    session.activeSubIndexMap[questionIndex] = safe;
  }

  bool canGoNextSubQuestion() {
    final item = session.currentQuestion;
    if (!_hasSubQuestions(item)) return false;
    final current = _currentActiveSubIndex(item!);
    return current >= 0 && current < item.subQuestions.length - 1;
  }

  bool canGoPrevSubQuestion() {
    final item = session.currentQuestion;
    if (!_hasSubQuestions(item)) return false;
    return _currentActiveSubIndex(item!) > 0;
  }

  bool goNextSubQuestion() {
    final item = session.currentQuestion;
    if (!_hasSubQuestions(item)) return false;
    final current = _currentActiveSubIndex(item!);
    if (current < 0 || current >= item.subQuestions.length - 1) return false;

    _submit.calculateRemainTime();
    final data = session.panelKey?.currentState?.getChildData();
    _submit.questionRenewTimeFn(
      data?.data ?? QuestionModel(<String, dynamic>{}),
      session.currentQuestion?.id ?? '',
    );
    session.activeSubIndexMap[session.currentIndex] = current + 1;
    bridge.notifyListeners();
    return true;
  }

  bool goPrevSubQuestion() {
    final item = session.currentQuestion;
    if (!_hasSubQuestions(item)) return false;
    final current = _currentActiveSubIndex(item!);
    if (current <= 0) return false;

    _submit.calculateRemainTime();
    final data = session.panelKey?.currentState?.getChildData();
    _submit.questionRenewTimeFn(
      data?.data ?? QuestionModel(<String, dynamic>{}),
      session.currentQuestion?.id ?? '',
    );
    session.activeSubIndexMap[session.currentIndex] = current - 1;
    bridge.notifyListeners();
    return true;
  }

  /// 答题卡定位（对标 handleAnswerCardSelect）
  Future<void> handleAnswerCardSelect(Map<String, dynamic> question) async {
    final currentQuestionIndex = session.currentIndex;
    final currentInfo = session.currentQuestion;
    final currentActiveSubIndex =
        currentInfo == null ? -1 : _currentActiveSubIndex(currentInfo);

    var targetQuestionIndex = -1;
    var targetSubIndex = -1;

    final parentIndex = question['parentIndex'];
    if (parentIndex is int && parentIndex >= 0) {
      targetQuestionIndex = parentIndex;
      targetSubIndex = int.tryParse('${question['subIndex'] ?? -1}') ?? -1;
    } else {
      final displaySort = int.tryParse('${question['sort'] ?? 0}') ?? 0;
      if (displaySort == 0) return;
      final resolved = resolveTargetByDisplaySort(displaySort);
      targetQuestionIndex = resolved.questionIndex;
      targetSubIndex = resolved.subIndex;
    }

    if (targetQuestionIndex < 0) return;

    final shouldSubmitBeforeJump =
        targetQuestionIndex != currentQuestionIndex ||
            (targetQuestionIndex == currentQuestionIndex &&
                targetSubIndex >= 0 &&
                targetSubIndex != currentActiveSubIndex);
    if (!session.isView && shouldSubmitBeforeJump) {
      // 只触发提交，不 await，避免跳题卡顿
      submitCurrentQuestionBeforePageSwitch();
    }

    if (targetSubIndex >= 0) {
      final targetItem = targetQuestionIndex >= 0 &&
              targetQuestionIndex < session.questions.length
          ? session.questions[targetQuestionIndex]
          : null;
      final subTotal = targetItem?.subQuestions.length ?? 0;
      if (subTotal > 0) {
        targetSubIndex = targetSubIndex > subTotal - 1 ? subTotal - 1 : targetSubIndex;
        if (targetSubIndex < 0) targetSubIndex = 0;
        session.activeSubIndexMap[targetQuestionIndex] = targetSubIndex;
        session.pendingSubIndexMap[targetQuestionIndex] = targetSubIndex;
      } else {
        targetSubIndex = -1;
      }
    }

    if (targetQuestionIndex != currentQuestionIndex) {
      markProgrammaticJump();
      _submit.calculateRemainTime();
      await Future<void>.delayed(const Duration(milliseconds: 500));
      bridge.jumpToPage(targetQuestionIndex);
      return;
    }

    if (targetSubIndex >= 0) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        session.itemRefs[targetQuestionIndex]
            ?.currentState
            ?.setActiveSubIndex(targetSubIndex);
      });
      bridge.notifyListeners();
    }
  }

  /// 触发当前页“上传笔记”
  Future<void>? uploadNotes() {
    return session.itemRefs[session.currentIndex]
        ?.currentState
        ?.uploadLectureNotes();
  }

  /// 下一题（含复合题内部下一小题）
  void nextStep() {
    if (canGoNextSubQuestion()) {
      goNextSubQuestion();
      return;
    }
    submitCurrentQuestionBeforePageSwitch();
    if (session.currentIndex == session.questions.length - 1) return;
    markProgrammaticJump();
    bridge.jumpToPage(session.currentIndex + 1);
  }

  /// 上一题（含复合题内部上一小题）
  void previousStep() {
    if (canGoPrevSubQuestion()) {
      goPrevSubQuestion();
      return;
    }
    if (session.currentIndex == 0) return;
    submitCurrentQuestionBeforePageSwitch();
    markProgrammaticJump();
    bridge.jumpToPage(session.currentIndex - 1);
  }

  /// 顶部返回：通知页面打开退出确认弹窗
  void clickBackNavBar() {
    bridge.openExitPopup();
  }

  /// 底部上一题 / 下一题统一入口（对标 switchStep）
  void switchStep(String type, [String? timePopupIfNeeded]) {
    if (session.currentIndex == 0 &&
        type == 'PreviousStep' &&
        !canGoPrevSubQuestion()) {
      return;
    }

    if (type == 'NextStep') {
      // 最低学习时长只拦“跨大题”，不拦大题内子题切换
      if (timePopupIfNeeded != 'minimumLearningDuration') {
        if (!canGoNextSubQuestion() && openTimePopup()) return;
      }
      if (openUploadNotesPopup()) return;

      if (currentSortLabel == totalSortCount) {
        submitExamPaper('submit');
        return;
      }
      nextStep();
    } else if (type == 'PreviousStep') {
      previousStep();
    }
  }

  /// view 最后一题“完成”：回攻克列表
  void completeEnd() {
    bridge.relaunchCaptureList(session.courseId);
  }

  void dispose() {
    _programmaticJumpTimer?.cancel();
  }
}