English/kouyu_english/lib/features/lesson/lesson_flow.dart

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';

part 'steps/independent_step.dart';
part 'steps/listening_step.dart';
part 'steps/preview_step.dart';
part 'steps/reading_step.dart';
part 'steps/speaking_step.dart';
part 'steps/writing_step.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 _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 _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'),
      ),
    ],
  );
}