English/kouyu_english/lib/features/lesson/steps/writing_step.dart

part of '../lesson_flow.dart';

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;

  Future<void> _submit() async {
    if (!widget.canContinue || requestingAiFeedback) return;
    final answer = widget.controller.text.trim();
    final local = WritingFeedback.check(widget.segmentId, answer);
    setState(() {
      result = local;
      aiFeedback = null;
      aiFeedbackError = null;
    });
    if (!local.complete) return;
    if (widget.state.aiProvider == AiProviderType.mock) {
      widget.onContinue(false);
      return;
    }
    setState(() {
      requestingAiFeedback = true;
      aiFeedbackError = null;
    });
    final feedback = await AiService.instance.capabilities.evaluation
        .evaluateWriting(
          provider: widget.state.aiProvider,
          endpoint: widget.state.aiEndpoint,
          model: widget.state.aiModel,
          lessonId: widget.lessonId,
          taskPrompt: widget.activity.writingPrompt,
          answer: answer,
          level: lessonLevel(widget.lessonId),
        );
    if (!mounted || widget.controller.text.trim() != answer) {
      if (mounted) setState(() => requestingAiFeedback = false);
      return;
    }
    if (feedback?.verdict == 'accepted') {
      widget.onContinue(true);
      return;
    }
    setState(() {
      requestingAiFeedback = false;
      aiFeedback = feedback;
      aiFeedbackError = feedback == null || feedback.verdict == 'uncertain'
          ? '答案暂时无法核验。可以重试，或仅保存这次练习继续学习。'
          : null;
    });
  }

  void _continueUnverified() => widget.onContinue(false);

  @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,
        ),
        if (widget.state.aiProvider == AiProviderType.mock)
          SectionCard(
            tint: AppColors.warm,
            child: const Text('尚未配置 AI 服务。本次可继续练习，但开放回答不会计入独立掌握。'),
          ),
        SectionCard(
          tint: AppColors.surfaceMuted,
          child: Text('小提示：${grammarNoteForSegment(widget.segmentId)}'),
        ),
        SegmentUsage(segmentId: widget.segmentId, state: widget.state),
        if (widget.showHelp)
          SectionCard(
            tint: AppColors.softGreen,
            child: Text(
              widget.activity.writingExample,
              style: TextStyle(fontSize: 18, height: 1.5),
            ),
          ),
        TextField(
          controller: widget.controller,
          onChanged: (_) {
            setState(() {
              result = null;
              aiFeedback = null;
              aiFeedbackError = null;
            });
            widget.onChanged();
          },
          minLines: 3,
          maxLines: 4,
          decoration: InputDecoration(
            labelText: '你的答案',
            hintText: widget.showHelp
                ? widget.activity.writingExample
                : '请输入完整英文答案',
            filled: true,
            fillColor: AppColors.surface,
            border: const OutlineInputBorder(),
          ),
        ),
        TextButton(
          onPressed: widget.onToggleHelp,
          child: Text(widget.showHelp ? '收起示例，自己试一次' : '需要帮助，查看示例'),
        ),
        if (aiFeedback != null)
          SectionCard(
            tint: aiFeedback!.verdict == 'accepted'
                ? AppColors.softGreen
                : AppColors.warm,
            child: SpacedColumn(
              spacing: 6,
              children: [
                Text('AI 建议：${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}'),
                Text(
                  aiFeedback!.verdict == 'rewrite'
                      ? '请按自己的意思修改，再提交检查。看过改正后，本次只算辅助练习。'
                      : '答案尚未核验；可以重试检查或仅保存练习。',
                  style: TextStyle(fontSize: 12, color: AppColors.muted),
                ),
              ],
            ),
          ),
        if (aiFeedbackError != null)
          SectionCard(
            tint: AppColors.warm,
            child: Text(
              aiFeedbackError!,
              style: TextStyle(color: AppColors.warmInk),
            ),
          ),
        if (result != null && !result!.complete)
          SectionCard(
            tint: AppColors.warm,
            child: Text(
              result!.message,
              style: TextStyle(color: AppColors.warmInk),
            ),
          ),
        PrimaryButton(
          label: requestingAiFeedback ? '正在自动检查…' : '提交并继续',
          onPressed: widget.canContinue && !requestingAiFeedback
              ? _submit
              : null,
        ),
        if (aiFeedbackError != null)
          TextButton(
            onPressed: _continueUnverified,
            child: const Text('未核验，保存练习并继续'),
          ),
      ],
    ),
  );
}