import 'package:flutter/material.dart';

import '../../core/app_state.dart';
import '../../core/ai_service.dart';
import '../../core/app_theme.dart';
import '../../core/models.dart';
import '../../core/seed_courses.dart';
import '../../core/voice_service.dart';
import '../../core/writing_feedback.dart';
import '../../widgets/app_widgets.dart';
import '../../widgets/lexicon_lookup.dart';
import '../../widgets/voice_answer.dart';

class LessonFlow extends StatefulWidget {
  const LessonFlow({
    super.key,
    required this.state,
    required this.onOpenDialogue,
    required this.onFinish,
  });

  final AppState state;
  final VoidCallback onOpenDialogue;
  final VoidCallback onFinish;

  @override
  State<LessonFlow> createState() => _LessonFlowState();
}

class _LessonFlowState extends State<LessonFlow> {
  final writingController = TextEditingController();
  final independentController = TextEditingController();
  int selectedAnswer = -1;
  int previewIndex = 0;
  bool listeningAudioPlayed = false;
  bool showWritingHelp = true;
  bool showIndependentHelp = false;
  LessonSegment get segment {
    final lesson = lessonById(widget.state.activeLessonId);
    return lesson.segments[widget.state.activeSegmentIndexFor(lesson.id)];
  }

  LessonActivity get activity =>
      activityBySegmentId(segment.id, widget.state.activeLessonId);

  List<VocabularyItem> get previewItems =>
      vocabularyBySegmentId(segment.id, widget.state.activeLessonId);

  @override
  void initState() {
    super.initState();
    writingController.text = widget.state.lessonWritingDraft;
    independentController.text = widget.state.independentAttemptDraft;
    previewIndex = widget.state.previewIndex
        .clamp(0, previewItems.length - 1)
        .toInt();
  }

  @override
  void dispose() {
    writingController.dispose();
    independentController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final lesson = lessonById(widget.state.activeLessonId);
    final Widget content;
    switch (widget.state.lessonStep) {
      case LessonStep.preview:
        content = _PreviewStep(
          state: widget.state,
          item: previewItems[previewIndex],
          position: previewIndex + 1,
          total: previewItems.length,
          onLookup: () => showLexiconLookup(
            context,
            state: widget.state,
            initialText: previewItems[previewIndex].word,
          ),
          onNext: () {
            if (previewIndex < previewItems.length - 1) {
              setState(() => previewIndex += 1);
              widget.state.setPreviewIndex(previewIndex);
            } else {
              widget.state.completePreview();
            }
          },
          onSkip: widget.state.completePreview,
        );
      case LessonStep.listening:
        final listeningOptions = shuffledOptions(
          activity.answers,
          '${activity.listening}-listening',
        );
        content = _ListeningStep(
          state: widget.state,
          activity: activity,
          options: listeningOptions,
          correctAnswer: activity.answers.first,
          selectedAnswer: selectedAnswer,
          audioPlayed: listeningAudioPlayed,
          onSelected: (value) => setState(() => selectedAnswer = value),
          onPlayed: () => setState(() => listeningAudioPlayed = true),
          onLookup: () => showLexiconLookup(
            context,
            state: widget.state,
            initialText: activity.listening,
          ),
          onContinue:
              selectedAnswer >= 0 &&
                  listeningOptions[selectedAnswer] == activity.answers.first
              ? widget.state.completeListening
              : null,
        );
      case LessonStep.speaking:
        content = _SpeakingStep(
          state: widget.state,
          text: activity.speaking,
          keepRecording: widget.state.keepRecordings,
          onContinue: () => widget.state.completeSpeaking(assisted: true),
        );
      case LessonStep.reading:
        content = _ReadingStep(
          state: widget.state,
          activity: activity,
          onLookup: () => showLexiconLookup(
            context,
            state: widget.state,
            initialText: activity.reading,
          ),
          onContinue: widget.state.completeReading,
        );
      case LessonStep.writing:
        content = _WritingStep(
          state: widget.state,
          lessonId: widget.state.activeLessonId,
          segmentId: segment.id,
          activity: activity,
          controller: writingController,
          showHelp: showWritingHelp,
          canContinue: writingController.text.trim().isNotEmpty,
          onChanged: () {
            widget.state.setLessonWritingDraft(writingController.text);
            setState(() {});
          },
          onToggleHelp: () =>
              setState(() => showWritingHelp = !showWritingHelp),
          onContinue: (usedAiFeedback) => widget.state.completeWriting(
            assisted: showWritingHelp || usedAiFeedback,
            rawAnswer: writingController.text.trim(),
          ),
        );
      case LessonStep.dialogue:
        content = _DialoguePendingStep(onOpenDialogue: widget.onOpenDialogue);
      case LessonStep.independent:
        content = _IndependentStep(
          state: widget.state,
          segmentId: segment.id,
          keepRecording: widget.state.keepRecordings,
          activity: activity,
          controller: independentController,
          showHelp: showIndependentHelp,
          canContinue: independentController.text.trim().isNotEmpty,
          onChanged: () {
            widget.state.setIndependentAttemptDraft(independentController.text);
            setState(() {});
          },
          onNeedHelp: () => setState(() => showIndependentHelp = true),
          onLookup: () {
            setState(() => showIndependentHelp = true);
            showLexiconLookup(
              context,
              state: widget.state,
              initialText: activity.independentPrompt,
            );
          },
          onContinue: (spoken, recordingPath) =>
              widget.state.completeIndependentAttempt(
                assisted: showIndependentHelp,
                spoken: spoken,
                rawAnswer: independentController.text.trim(),
                recordingPath: recordingPath,
              ),
          onLater: () =>
              widget.state.completeIndependentAttempt(assisted: true),
        );
      case LessonStep.complete:
        content = _CompletionStep(
          assisted: widget.state.independentAttemptAssisted,
          isFinalSegment:
              widget.state.activeSegmentIndexFor(lesson.id) ==
              lesson.segments.length - 1,
          nextSegmentNumber: widget.state.activeSegmentIndexFor(lesson.id) + 2,
          onFinish: () {
            widget.state.finishCurrentLessonSegment();
            widget.onFinish();
          },
        );
    }
    return _LessonScope(
      title:
          '第 ${lesson.number} 课 · ${lesson.title} · 第 ${widget.state.activeSegmentIndexFor(lesson.id) + 1}/${lesson.segments.length} 段',
      onExit: widget.onFinish,
      child: content,
    );
  }
}

class _LessonScaffold extends StatelessWidget {
  const _LessonScaffold({required this.step, required this.child});

  final int step;
  final Widget child;

  @override
  Widget build(BuildContext context) => AppPage(
    appBar: AppBar(
      leading: IconButton(
        icon: const Icon(Icons.arrow_back),
        tooltip: "退出课程",
        onPressed: () {
          final onExit = _LessonScope.exitOf(context);
          if (onExit != null) {
            onExit();
          } else if (Navigator.canPop(context)) {
            Navigator.pop(context);
          }
        },
      ),
      title: Text(_LessonScope.of(context)),
    ),
    child: SpacedColumn(
      spacing: 16,
      children: [
        Row(
          children: List.generate(
            6,
            (index) => Expanded(
              child: Container(
                height: 6,
                margin: EdgeInsets.only(right: index == 5 ? 0 : 5),
                decoration: BoxDecoration(
                  color: index < step ? AppColors.green : AppColors.line,
                  borderRadius: BorderRadius.circular(20),
                ),
              ),
            ),
          ),
        ),
        child,
      ],
    ),
  );
}

class _LessonScope extends InheritedWidget {
  const _LessonScope({
    required this.title,
    this.onExit,
    required super.child,
  });

  final String title;
  final VoidCallback? onExit;

  static String of(BuildContext context) =>
      context.dependOnInheritedWidgetOfExactType<_LessonScope>()?.title ??
      'A0 课程练习';

  static VoidCallback? exitOf(BuildContext context) =>
      context.dependOnInheritedWidgetOfExactType<_LessonScope>()?.onExit;

  @override
  bool updateShouldNotify(_LessonScope oldWidget) =>
      title != oldWidget.title || onExit != oldWidget.onExit;
}

class _PreviewStep extends StatelessWidget {
  const _PreviewStep({
    required this.state,
    required this.item,
    required this.position,
    required this.total,
    required this.onLookup,
    required this.onNext,
    required this.onSkip,
  });

  final VocabularyItem item;
  final AppState state;
  final int position;
  final int total;
  final VoidCallback onLookup;
  final VoidCallback onNext;
  final VoidCallback onSkip;

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 1,
    child: SpacedColumn(
      children: [
        Eyebrow('先认识今天的词 · $position / $total'),
        Text('后面会遇到这些词。', style: Theme.of(context).textTheme.headlineMedium),
        const Text('先听一遍、知道意思就够了，不用马上背会。'),
        SectionCard(
          tint: AppColors.softGreen,
          child: SpacedColumn(
            children: [
              Text(
                item.word,
                style: const TextStyle(
                  fontSize: 28,
                  fontWeight: FontWeight.w600,
                ),
              ),
              if (item.ipa != null)
                Text(item.ipa!, style: Theme.of(context).textTheme.bodyMedium),
              Text(item.meaning, style: const TextStyle(fontSize: 17)),
              _AudioRow(label: '播放示范音', speech: item.word),
              LexiconText(item.example, state: state),
              Text(item.exampleMeaning),
            ],
          ),
        ),
        Wrap(
          spacing: 8,
          children: [ActionChip(label: const Text('查词'), onPressed: onLookup)],
        ),
        PrimaryButton(
          label: position == total ? '进入课程' : '认识了，下一个',
          onPressed: onNext,
        ),
        TextButton(onPressed: onSkip, child: const Text('跳过，直接进入课程')),
      ],
    ),
  );
}

class _ListeningStep extends StatelessWidget {
  const _ListeningStep({
    required this.state,
    required this.activity,
    required this.options,
    required this.correctAnswer,
    required this.selectedAnswer,
    required this.audioPlayed,
    required this.onSelected,
    required this.onPlayed,
    required this.onLookup,
    required this.onContinue,
  });

  final LessonActivity activity;
  final AppState state;
  final List<String> options;
  final String correctAnswer;

  final int selectedAnswer;
  final bool audioPlayed;
  final ValueChanged<int> onSelected;
  final VoidCallback onPlayed;
  final VoidCallback onLookup;
  final VoidCallback? onContinue;

  @override
  Widget build(BuildContext context) {
    final answers = options;
    return _LessonScaffold(
      step: 2,
      child: SpacedColumn(
        spacing: 14,
        children: [
          const Eyebrow('听一听'),
          Text(
            activity.listeningQuestion,
            style: Theme.of(context).textTheme.headlineMedium,
          ),
          SectionCard(
            tint: AppColors.surfaceMuted,
            child: _AudioRow(
              label: audioPlayed ? '再播放一次' : '播放问题',
              speech: activity.listening,
              onPlayed: onPlayed,
            ),
          ),
          TextButton.icon(
            onPressed: onLookup,
            icon: const Icon(Icons.menu_book_outlined),
            label: const Text('查看词或短语'),
          ),
          if (audioPlayed)
            SectionCard(child: LexiconText(activity.listening, state: state)),
          for (var index = 0; index < answers.length; index++)
            SectionCard(
              tint: selectedAnswer == index ? AppColors.softGreen : null,
              onTap: () {
                onSelected(index);
                if (!audioPlayed) {
                  onPlayed();
                }
              },
              child: Row(
                children: [
                  Icon(
                    selectedAnswer == index
                        ? Icons.radio_button_checked
                        : Icons.radio_button_off,
                    color: selectedAnswer == index
                        ? AppColors.green
                        : AppColors.muted,
                  ),
                  const SizedBox(width: 10),
                  Text(answers[index]),
                ],
              ),
            ),
          PrimaryButton(
            label: selectedAnswer >= 0
                ? '检查并继续'
                : (audioPlayed ? '请选择答案' : '先播放音频或选择答案'),
            onPressed: onContinue,
          ),
          if (selectedAnswer >= 0 && answers[selectedAnswer] != correctAnswer)
            const Text(
              '再听一次，选择正确答案。',
              style: TextStyle(color: AppColors.warmInk),
            ),
        ],
      ),
    );
  }
}

class _SpeakingStep extends StatefulWidget {
  const _SpeakingStep({
    required this.state,
    required this.text,
    required this.keepRecording,
    required this.onContinue,
  });
  final String text;
  final AppState state;
  final bool keepRecording;
  final VoidCallback onContinue;

  @override
  State<_SpeakingStep> createState() => _SpeakingStepState();
}

class _SpeakingStepState extends State<_SpeakingStep>
    with VoiceAnswerMixin<_SpeakingStep> {
  String transcript = '';

  @override
  AppState get voiceState => widget.state;

  @override
  void dispose() {
    disposeVoiceAnswer(keepRecording: widget.keepRecording);
    super.dispose();
  }

  Future<void> _toggleMic() async {
    if (aiVoiceRecording) {
      await finishVoiceInput(
        noSpeech: '未识别到清晰发音，请重试或点击“播放示范音”。',
        onTranscript: (text) => transcript = text,
      );
      return;
    }

    await VoiceService.instance.stopRecordingPlayback();
    if (mounted) setState(() => playingRecording = false);
    if (!widget.keepRecording) {
      await VoiceService.instance.deleteRecording(recordingPath);
    }

    final recordStarted = await startVoiceInput();
    if (!recordStarted || !mounted) return;
    setState(() => recordingPath = null);
    showVoiceMessage('已启动麦克风录音，跟读完成后再次点击，AI 将自动转写发音。');
  }

  Future<void> _togglePlayRecording() async {
    if (playingRecording) {
      await VoiceService.instance.stopRecordingPlayback();
      if (mounted) setState(() => playingRecording = false);
      return;
    }
    if (recordingPath == null) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('请先使用麦克风跟读，录音完成后即可播放。')),
      );
      return;
    }
    await playRecording();
  }

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 3,
    child: SpacedColumn(
      children: [
        const Eyebrow('跟读'),
        Text('先听，再说。', style: Theme.of(context).textTheme.headlineMedium),
        LexiconText(
          widget.text,
          state: widget.state,
          textAlign: TextAlign.center,
          style: const TextStyle(fontSize: 30, fontWeight: FontWeight.w600),
        ),
        Text(
          '/es - eɪtʃ - iː - en/',
          style: Theme.of(context).textTheme.bodyMedium,
        ),
        SectionCard(
          tint: AppColors.surfaceMuted,
          child: _AudioRow(label: '播放示范音', speech: widget.text),
        ),
        const SectionCard(
          tint: AppColors.warm,
          child: Text(
            '字母之间留一个短停顿。先清楚，不必快。',
            style: TextStyle(color: AppColors.warmInk),
          ),
        ),
        SecondaryButton(
          label: transcribing
              ? '正在 AI 识别发音…'
              : (listening ? '停止录音并识别' : '使用麦克风跟读'),
          onPressed: transcribing ? null : _toggleMic,
        ),
        SecondaryButton(
          label: playingRecording ? '停止播放' : '播放跟读',
          onPressed: (listening || transcribing) ? null : _togglePlayRecording,
        ),
        if (recordingPath != null)
          SectionCard(
            tint: AppColors.softGreen,
            child: SpacedColumn(
              spacing: 8,
              children: [
                Text(widget.keepRecording ? '录音已保存在本机。' : '本次跟读录音仅在离开此步骤前保留。'),
                Row(
                  children: [
                    Expanded(
                      child: OutlinedButton.icon(
                        onPressed: (listening || transcribing) ? null : _togglePlayRecording,
                        icon: Icon(playingRecording ? Icons.stop : Icons.play_arrow),
                        label: Text(playingRecording ? '停止播放' : '播放跟读'),
                      ),
                    ),
                    const SizedBox(width: 8),
                    IconButton(
                      tooltip: '删除录音',
                      onPressed: (listening || transcribing) ? null : deleteRecording,
                      icon: const Icon(Icons.delete_outline),
                    ),
                  ],
                ),
              ],
            ),
          ),
        if (transcript.isNotEmpty)
          SectionCard(
            child: Text("设备转写：$transcript\n请确认它是否接近你刚才说的内容。"),
          ),
        const SectionCard(
          child: Text('转写不确定或与原句不符时，可重说或继续文字练习；这一步只算跟读练习，不作为独立口语证据。'),
        ),
        PrimaryButton(
          label: transcript.isEmpty ? '我已跟读，继续' : '确认并继续',
          onPressed: widget.onContinue,
        ),
      ],
    ),
  );
}

class _ReadingStep extends StatefulWidget {
  const _ReadingStep({
    required this.state,
    required this.activity,
    required this.onLookup,
    required this.onContinue,
  });
  final LessonActivity activity;
  final AppState state;
  final VoidCallback onLookup;
  final VoidCallback onContinue;

  @override
  State<_ReadingStep> createState() => _ReadingStepState();
}

class _ReadingStepState extends State<_ReadingStep> {
  final controller = TextEditingController();
  int? selectedOptionIndex;
  bool showAnswer = false;

  /// 打乱后的选项：答案不再固定排在第一位，但同一道题顺序保持稳定。
  late final List<String> options = shuffledOptions(
    widget.activity.readingOptions,
    '${widget.activity.readingQuestion}-reading',
  );

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

  bool _isOptionCorrect(int index) {
    if (options.isEmpty || index < 0 || index >= options.length) {
      return false;
    }
    final option = options[index].trim();
    final answer = widget.activity.readingAnswer.trim();
    if (option.toLowerCase() == answer.toLowerCase()) return true;

    final normOption = option
        .toLowerCase()
        .replaceAll(RegExp(r'[^a-z0-9\u4e00-\u9fa5]'), '');
    final normAnswer = answer
        .toLowerCase()
        .replaceAll(RegExp(r'[^a-z0-9\u4e00-\u9fa5]'), '');
    return normOption.isNotEmpty &&
        normAnswer.isNotEmpty &&
        (normOption.contains(normAnswer) || normAnswer.contains(normOption));
  }

  bool get isOptionMode => options.isNotEmpty;

  bool get isCorrect {
    if (isOptionMode) {
      return selectedOptionIndex != null && _isOptionCorrect(selectedOptionIndex!);
    }
    final answer = widget.activity.readingAnswer.toLowerCase().replaceAll(
      RegExp(r'[^a-z0-9\u4e00-\u9fa5]'),
      '',
    );
    final response = controller.text.toLowerCase().replaceAll(
      RegExp(r'[^a-z0-9\u4e00-\u9fa5]'),
      '',
    );
    // 只接受写全了答案的输入：过去反向的 answer.contains(response) 让单个字母
    // 也能判对（'a' 通过 'A book'）。
    return response.isNotEmpty && answer.isNotEmpty && response.contains(answer);
  }

  @override
  Widget build(BuildContext context) {
    final hasSelected = selectedOptionIndex != null;
    final answeredCorrectly = isCorrect;

    return _LessonScaffold(
      step: 4,
      child: SpacedColumn(
        children: [
          const Eyebrow('读一读'),
          Text('在对话里找到答案。', style: Theme.of(context).textTheme.headlineMedium),
          SectionCard(
            tint: AppColors.softGreen,
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    const Row(
                      children: [
                        Icon(Icons.chat_bubble_outline, size: 16, color: AppColors.green),
                        SizedBox(width: 6),
                        Text(
                          '对话内容',
                          style: TextStyle(
                            fontSize: 13,
                            fontWeight: FontWeight.w600,
                            color: AppColors.green,
                          ),
                        ),
                      ],
                    ),
                    InkWell(
                      onTap: () => VoiceService.instance.speak(widget.activity.reading),
                      borderRadius: BorderRadius.circular(16),
                      child: const Padding(
                        padding: EdgeInsets.symmetric(horizontal: 8, vertical: 4),
                        child: Row(
                          children: [
                            Icon(Icons.volume_up_outlined, size: 16, color: AppColors.green),
                            SizedBox(width: 4),
                            Text('朗读对话', style: TextStyle(fontSize: 13, color: AppColors.green)),
                          ],
                        ),
                      ),
                    ),
                  ],
                ),
                const SizedBox(height: 8),
                LexiconText(
                  widget.activity.reading,
                  state: widget.state,
                  style: const TextStyle(fontSize: 16, height: 1.6),
                ),
              ],
            ),
          ),
          Row(
            children: [
              TextButton.icon(
                onPressed: widget.onLookup,
                icon: const Icon(Icons.menu_book_outlined, size: 18),
                label: const Text('查词或短语'),
              ),
              const SizedBox(width: 8),
              TextButton.icon(
                onPressed: () {
                  final lines = widget.activity.reading.split('\n');
                  final target = lines.firstWhere(
                    (l) => l.trim().isNotEmpty,
                    orElse: () => widget.activity.reading,
                  ).replaceFirst(RegExp(r'^[A-Za-z]+:\s*'), '');
                  showLexiconLookup(
                    context,
                    state: widget.state,
                    initialText: target,
                  );
                },
                icon: const Icon(Icons.auto_stories_outlined, size: 18),
                label: const Text('句型深度解析'),
              ),
            ],
          ),
          SectionCard(
            tint: AppColors.surfaceMuted,
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Container(
                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 2),
                  decoration: BoxDecoration(
                    color: AppColors.green.withValues(alpha: 0.12),
                    borderRadius: BorderRadius.circular(6),
                  ),
                  child: const Text(
                    '问题',
                    style: TextStyle(
                      color: AppColors.green,
                      fontWeight: FontWeight.bold,
                      fontSize: 12,
                    ),
                  ),
                ),
                const SizedBox(width: 10),
                Expanded(
                  child: Text(
                    widget.activity.readingQuestion,
                    style: const TextStyle(
                      fontSize: 15,
                      fontWeight: FontWeight.w600,
                      color: AppColors.ink,
                    ),
                  ),
                ),
              ],
            ),
          ),
          if (isOptionMode) ...[
            for (var index = 0; index < options.length; index++) ...[
              SectionCard(
                tint: selectedOptionIndex == index
                    ? (_isOptionCorrect(index) ? AppColors.softGreen : AppColors.warm)
                    : null,
                onTap: () {
                  setState(() {
                    selectedOptionIndex = index;
                    showAnswer = false;
                  });
                },
                child: Row(
                  children: [
                    Icon(
                      selectedOptionIndex == index
                          ? (_isOptionCorrect(index) ? Icons.check_circle : Icons.cancel_outlined)
                          : Icons.radio_button_off,
                      color: selectedOptionIndex == index
                          ? (_isOptionCorrect(index) ? AppColors.green : AppColors.warmInk)
                          : AppColors.muted,
                    ),
                    const SizedBox(width: 12),
                    Expanded(
                      child: Text(
                        options[index],
                        style: TextStyle(
                          fontSize: 15,
                          fontWeight: selectedOptionIndex == index ? FontWeight.w600 : FontWeight.normal,
                          color: selectedOptionIndex == index
                              ? (_isOptionCorrect(index) ? AppColors.green : AppColors.warmInk)
                              : AppColors.ink,
                        ),
                      ),
                    ),
                  ],
                ),
              ),
            ],
            if (hasSelected && answeredCorrectly)
              Container(
                padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
                decoration: BoxDecoration(
                  color: AppColors.softGreen,
                  borderRadius: BorderRadius.circular(10),
                  border: Border.all(color: AppColors.green.withValues(alpha: 0.3)),
                ),
                child: const Row(
                  children: [
                    Icon(Icons.check_circle, color: AppColors.green, size: 20),
                    SizedBox(width: 8),
                    Expanded(
                      child: Text(
                        '回答正确！点击下方按钮继续',
                        style: TextStyle(
                          color: AppColors.green,
                          fontWeight: FontWeight.w600,
                          fontSize: 14,
                        ),
                      ),
                    ),
                  ],
                ),
              )
            else if (hasSelected && !answeredCorrectly)
              Container(
                padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
                decoration: BoxDecoration(
                  color: AppColors.warm,
                  borderRadius: BorderRadius.circular(10),
                  border: Border.all(color: AppColors.warmInk.withValues(alpha: 0.2)),
                ),
                child: const Row(
                  children: [
                    Icon(Icons.help_outline, color: AppColors.warmInk, size: 20),
                    SizedBox(width: 8),
                    Expanded(
                      child: Text(
                        '不对哦，再仔细观察对话中的关键句子～',
                        style: TextStyle(color: AppColors.warmInk, fontSize: 13),
                      ),
                    ),
                  ],
                ),
              ),
          ] else ...[
            TextField(
              controller: controller,
              onChanged: (_) => setState(() {}),
              decoration: const InputDecoration(
                hintText: '用英文输入答案',
                filled: true,
                fillColor: AppColors.surface,
                border: OutlineInputBorder(),
              ),
            ),
          ],
          if (showAnswer)
            SectionCard(
              tint: AppColors.warm,
              child: Text(
                '答案：${widget.activity.readingAnswer}',
                style: const TextStyle(color: AppColors.warmInk),
              ),
            ),
          if (!showAnswer &&
              ((isOptionMode && hasSelected && !answeredCorrectly) ||
                  (!isOptionMode && controller.text.isNotEmpty && !answeredCorrectly)))
            TextButton(
              onPressed: () => setState(() => showAnswer = true),
              child: const Text('查看答案后继续学习'),
            ),
          PrimaryButton(
            label: showAnswer || answeredCorrectly
                ? '继续写一写'
                : (isOptionMode ? '请选择答案' : '检查并继续'),
            onPressed: showAnswer || answeredCorrectly ? widget.onContinue : null,
          ),
        ],
      ),
    );
  }
}

class _WritingStep extends StatefulWidget {
  const _WritingStep({
    required this.state,
    required this.lessonId,
    required this.segmentId,
    required this.activity,
    required this.controller,
    required this.showHelp,
    required this.canContinue,
    required this.onChanged,
    required this.onToggleHelp,
    required this.onContinue,
  });
  final String lessonId;
  final AppState state;
  final String segmentId;
  final LessonActivity activity;
  final TextEditingController controller;
  final bool showHelp;
  final bool canContinue;
  final VoidCallback onChanged;
  final VoidCallback onToggleHelp;
  final ValueChanged<bool> onContinue;

  @override
  State<_WritingStep> createState() => _WritingStepState();
}

class _WritingStepState extends State<_WritingStep> {
  WritingCheckResult? result;
  WritingAiFeedback? aiFeedback;
  String? aiFeedbackError;
  bool requestingAiFeedback = false;

  void _checkOrContinue() {
    if (result?.complete == true) {
      widget.onContinue(aiFeedback != null);
      return;
    }
    setState(
      () => result = WritingFeedback.check(
        widget.lessonId,
        widget.controller.text,
        segmentId: widget.segmentId,
      ),
    );
  }

  Future<void> _requestAiFeedback() async {
    if (widget.controller.text.trim().isEmpty || requestingAiFeedback) return;
    if (widget.state.aiProvider == AiProviderType.mock) {
      setState(() => aiFeedbackError = '请先在“我的”配置 AI 服务；本地检查仍可继续学习。');
      return;
    }
    setState(() {
      requestingAiFeedback = true;
      aiFeedbackError = null;
    });
    final feedback = await AiService.instance.writingFeedback(
      provider: widget.state.aiProvider,
      endpoint: widget.state.aiEndpoint,
      model: widget.state.aiModel,
      lessonId: widget.lessonId,
      taskPrompt: widget.activity.writingPrompt,
      answer: widget.controller.text.trim(),
    );
    if (!mounted) return;
    setState(() {
      requestingAiFeedback = false;
      aiFeedback = feedback;
      aiFeedbackError = feedback == null
          ? '暂时无法获得 AI 反馈。你的答案保留在这里，可稍后重试或继续本地练习。'
          : null;
    });
  }

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 5,
    child: SpacedColumn(
      children: [
        const Eyebrow('写一写'),
        Text(
          widget.activity.writingPrompt,
          style: Theme.of(context).textTheme.headlineMedium,
        ),
        SectionCard(
          tint: AppColors.surfaceMuted,
          child: Text(
            '小提示：${grammarNoteForSegment(widget.segmentId, widget.lessonId)}',
          ),
        ),
        if (widget.showHelp)
          SectionCard(
            tint: AppColors.softGreen,
            child: Text(
              widget.activity.writingExample,
              style: TextStyle(fontSize: 18, height: 1.5),
            ),
          ),
        TextField(
          controller: widget.controller,
          onChanged: (_) {
            setState(() {
              result = null;
              aiFeedback = null;
              aiFeedbackError = null;
            });
            widget.onChanged();
          },
          minLines: 3,
          maxLines: 4,
          decoration: InputDecoration(
            labelText: '你的答案',
            hintText: widget.showHelp
                ? widget.activity.writingExample
                : '请输入完整英文答案',
            filled: true,
            fillColor: AppColors.surface,
            border: const OutlineInputBorder(),
          ),
        ),
        TextButton(
          onPressed: widget.onToggleHelp,
          child: Text(widget.showHelp ? '收起示例，自己试一次' : '需要帮助，查看示例'),
        ),
        OutlinedButton.icon(
          onPressed: widget.canContinue && !requestingAiFeedback
              ? _requestAiFeedback
              : null,
          icon: requestingAiFeedback
              ? const SizedBox(
                  width: 16,
                  height: 16,
                  child: CircularProgressIndicator(strokeWidth: 2),
                )
              : const Icon(Icons.auto_awesome_outlined),
          label: Text(requestingAiFeedback ? '正在获取反馈…' : '获取 AI 写作建议（可选）'),
        ),
        if (aiFeedback != null)
          SectionCard(
            tint: aiFeedback!.verdict == 'accepted'
                ? AppColors.softGreen
                : AppColors.warm,
            child: SpacedColumn(
              spacing: 6,
              children: [
                Text('AI 建议：${aiFeedback!.feedback}'),
                if (aiFeedback!.missing.isNotEmpty)
                  Text('还可补充：${aiFeedback!.missing.join('、')}'),
                if (aiFeedback!.suggestion != null)
                  Text('可参考改写：${aiFeedback!.suggestion}'),
                const Text(
                  '这是学习帮助；请按自己的意思重写后再检查，系统不会仅凭 AI 建议记为掌握。',
                  style: TextStyle(fontSize: 12, color: AppColors.muted),
                ),
              ],
            ),
          ),
        if (aiFeedbackError != null)
          SectionCard(
            tint: AppColors.warm,
            child: Text(
              aiFeedbackError!,
              style: const TextStyle(color: AppColors.warmInk),
            ),
          ),
        if (result != null)
          SectionCard(
            tint: result!.complete ? AppColors.softGreen : AppColors.warm,
            child: Text(
              result!.message,
              style: TextStyle(
                color: result!.complete ? AppColors.green : AppColors.warmInk,
              ),
            ),
          ),
        PrimaryButton(
          label: result?.complete == true ? '进入课程对话' : '检查句子',
          onPressed: widget.canContinue ? _checkOrContinue : null,
        ),
      ],
    ),
  );
}

class _DialoguePendingStep extends StatelessWidget {
  const _DialoguePendingStep({required this.onOpenDialogue});
  final VoidCallback onOpenDialogue;

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 6,
    child: SpacedColumn(
      children: [
        const Eyebrow('课程对话'),
        Text('在情境中用上刚学的句子。', style: Theme.of(context).textTheme.headlineMedium),
        const Text('完成姓名、地点、一个状态或喜好，并反问对方。'),
        PrimaryButton(label: '开始文字对话', onPressed: onOpenDialogue),
      ],
    ),
  );
}

class _IndependentStep extends StatefulWidget {
  const _IndependentStep({
    required this.state,
    required this.segmentId,
    required this.keepRecording,
    required this.activity,
    required this.controller,
    required this.showHelp,
    required this.canContinue,
    required this.onChanged,
    required this.onNeedHelp,
    required this.onLookup,
    required this.onContinue,
    required this.onLater,
  });
  final AppState state;
  final LessonActivity activity;
  final String segmentId;
  final bool keepRecording;
  final TextEditingController controller;
  final bool showHelp;
  final bool canContinue;
  final VoidCallback onChanged;
  final VoidCallback onNeedHelp;
  final VoidCallback onLookup;
  final void Function(bool spoken, String? recordingPath) onContinue;
  final VoidCallback onLater;

  @override
  State<_IndependentStep> createState() => _IndependentStepState();
}

class _IndependentStepState extends State<_IndependentStep>
    with VoiceAnswerMixin<_IndependentStep> {
  bool usedVoice = false;
  bool transcriptEdited = false;
  String lastTranscript = '';
  String? validationError;

  @override
  AppState get voiceState => widget.state;

  @override
  void dispose() {
    disposeVoiceAnswer(keepRecording: widget.keepRecording);
    super.dispose();
  }

  void _submit() {
    if (!matchesSegmentIndependent(widget.segmentId, widget.controller.text)) {
      setState(() => validationError = '这次还没有用上本段要练的内容。查看帮助后补充一次。');
      return;
    }
    widget.onContinue(
      usedVoice && !transcriptEdited,
      widget.keepRecording ? recordingPath : null,
    );
  }

  Future<void> _toggleMic() async {
    if (aiVoiceRecording) {
      await finishVoiceInput(
        onTranscript: (text) {
          widget.controller.text = text;
          usedVoice = true;
          lastTranscript = text;
          transcriptEdited = false;
        },
        afterTranscribe: widget.onChanged,
      );
      return;
    }

    if (listening) {
      await VoiceService.instance.stopListening();
      if (mounted) setState(() => listening = false);
      return;
    }

    final ready = await VoiceService.instance.startListening(
      (text, _) {
        if (!mounted) return;
        setState(() {
          widget.controller.text = text;
          usedVoice = true;
          lastTranscript = text;
          transcriptEdited = false;
        });
        widget.onChanged();
      },
      onStatus: (status) {
        if (mounted && (status == 'notListening' || status == 'done')) {
          setState(() => listening = false);
        }
      },
      onError: (err) {
        if (mounted) {
          setState(() => listening = false);
        }
      },
    );

    if (!ready) {
      final recordStarted = await startVoiceInput();
      if (recordStarted && mounted) {
        showVoiceMessage('已启动麦克风录音，说完后再次点击，AI 将自动转写为英文。');
      }
      return;
    }

    if (mounted) setState(() => listening = ready);
  }

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 6,
    child: SpacedColumn(
      children: [
        const Eyebrow('试着自己写 / 说一次 · 约 1 分钟'),
        Text('现在不看句框。', style: Theme.of(context).textTheme.headlineMedium),
        Text(widget.activity.independentPrompt),
        if (widget.showHelp)
          SectionCard(
            tint: AppColors.warm,
            child: Text(
              '帮助：${widget.activity.independentHelp}',
              style: TextStyle(color: AppColors.warmInk),
            ),
          ),
        TextField(
          controller: widget.controller,
          onChanged: (value) {
            if (usedVoice && value != lastTranscript) transcriptEdited = true;
            setState(() {});
            widget.onChanged();
          },
          minLines: 2,
          maxLines: 4,
          decoration: InputDecoration(
            hintText: '输入完整英文句子',
            filled: true,
            fillColor: AppColors.surface,
            prefixIcon: IconButton(
              tooltip: listening ? '停止录音' : '语音输入',
              icon: Icon(
                listening ? Icons.stop_circle_outlined : Icons.mic_none,
              ),
              onPressed: _toggleMic,
            ),
            border: OutlineInputBorder(),
          ),
        ),
        SectionCard(
          tint: AppColors.surfaceMuted,
          child: SpacedColumn(
            spacing: 8,
            children: [
              Text(
                widget.keepRecording
                    ? '可录下这次尝试并保存在本机；不会发送给 AI。'
                    : '可录下这次尝试并回听；离开本页后会自动删除。',
              ),
              RecordingControls(
                recording: recording,
                playing: playingRecording,
                hasRecording: recordingPath != null,
                onToggleRecording: toggleRecording,
                onPlay: playRecording,
                onDelete: deleteRecording,
              ),
            ],
          ),
        ),
        if (usedVoice)
          SectionCard(
            tint: transcriptEdited ? AppColors.warm : AppColors.softGreen,
            child: Text(
              transcriptEdited
                  ? '你修改了设备转写：这次会按文字练习保存，不计口语练习。'
                  : '这是设备转写。未修改并确认后，会保留为本次语音练习记录。',
              style: TextStyle(
                color: transcriptEdited ? AppColors.warmInk : AppColors.green,
              ),
            ),
          ),
        if (validationError != null)
          SectionCard(
            tint: AppColors.warm,
            child: Text(
              validationError!,
              style: const TextStyle(color: AppColors.warmInk),
            ),
          ),
        if (!widget.showHelp)
          Wrap(
            spacing: 8,
            children: [
              TextButton(
                onPressed: widget.onNeedHelp,
                child: const Text('需要帮助'),
              ),
              TextButton(
                onPressed: widget.onLookup,
                child: const Text('查词或短语'),
              ),
            ],
          )
        else
          TextButton(onPressed: widget.onLookup, child: const Text('查词或短语')),
        PrimaryButton(
          label: widget.showHelp ? '带帮助完成' : '独立完成',
          onPressed: widget.canContinue ? _submit : null,
        ),
        TextButton(onPressed: widget.onLater, child: const Text('稍后继续')),
      ],
    ),
  );
}

class _CompletionStep extends StatelessWidget {
  const _CompletionStep({
    required this.assisted,
    required this.isFinalSegment,
    required this.nextSegmentNumber,
    required this.onFinish,
  });
  final bool assisted;
  final bool isFinalSegment;
  final int nextSegmentNumber;
  final VoidCallback onFinish;

  @override
  Widget build(BuildContext context) => _LessonScaffold(
    step: 6,
    child: SpacedColumn(
      children: [
        const Eyebrow('本段已保存'),
        Text(
          isFinalSegment ? '你完成了这节课的练习。' : '你完成了当前小段的练习。',
          style: Theme.of(context).textTheme.headlineMedium,
        ),
        Text(assisted ? '独立尝试使用了帮助，系统会安排不同题再练一次。' : '这次独立尝试已记录，后续会在不同情境中复练。'),
        if (!isFinalSegment) Text('回到首页后，下次从第 $nextSegmentNumber 段继续。'),
        PrimaryButton(label: '回到首页', onPressed: onFinish),
      ],
    ),
  );
}

class _AudioRow extends StatelessWidget {
  const _AudioRow({required this.label, this.speech, this.onPlayed});
  final String label;
  final String? speech;
  final VoidCallback? onPlayed;

  @override
  Widget build(BuildContext context) => Row(
    children: [
      IconButton.filled(
        onPressed: () async {
          try {
            await VoiceService.instance.speak(speech ?? label);
          } finally {
            onPlayed?.call();
          }
        },
        icon: const Icon(Icons.play_arrow),
      ),
      const SizedBox(width: 10),
      Expanded(
        child: InkWell(
          onTap: () async {
            try {
              await VoiceService.instance.speak(speech ?? label);
            } finally {
              onPlayed?.call();
            }
          },
          child: Padding(
            padding: const EdgeInsets.symmetric(vertical: 8.0),
            child: Text(label),
          ),
        ),
      ),
      TextButton(
        onPressed: () async {
          try {
            await VoiceService.instance.speak(speech ?? label, slow: true);
          } finally {
            onPlayed?.call();
          }
        },
        child: const Text('慢速'),
      ),
    ],
  );
}