import 'package:flutter/material.dart';

import '../../core/app_state.dart';
import '../../core/app_theme.dart';
import '../../core/courses/courses.dart';
import '../../widgets/app_widgets.dart';

/// 今天最该做的一件事：继续课程对话 → 到期复习 → 阶段评估/巩固 → 下一课。
class TodayTaskCard extends StatelessWidget {
  const TodayTaskCard({
    super.key,
    required this.state,
    required this.onStartLesson,
    required this.onStartReview,
    required this.onResumeLessonDialogue,
    required this.onStartReinforcement,
    required this.onOpenAssessment,
  });

  final AppState state;
  final VoidCallback onStartLesson;
  final VoidCallback onStartReview;
  final VoidCallback onResumeLessonDialogue;
  final VoidCallback onStartReinforcement;
  final ValueChanged<String> onOpenAssessment;

  @override
  Widget build(BuildContext context) {
    final task = _todayTask();
    return SectionCard(
      tint: AppColors.softGreen,
      child: SpacedColumn(
        children: [
          Row(
            children: [
              Expanded(child: Eyebrow(task.label)),
              Text(task.minutes, style: TextStyle(color: AppColors.green)),
            ],
          ),
          Text(
            task.title,
            style: const TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
          ),
          Text(task.note, style: Theme.of(context).textTheme.bodyMedium),
          PrimaryButton(label: task.action, onPressed: task.onPressed),
        ],
      ),
    );
  }

  _TodayTask _todayTask() {
    var lessonId = state.activeLessonId;
    if (state.completedLessonIds.contains(lessonId)) {
      final next = state.nextIncompleteLessonId;
      if (next != null) {
        lessonId = next;
      }
    }
    final lesson = lessonById(lessonId);

    if (state.hasResumableLessonDialogue) {
      return _TodayTask(
        label: '未完成',
        title: '继续第 ${lesson.number} 课的课程对话',
        note: '已保留你的对话进度和提示状态。',
        action: '继续对话',
        minutes: '5 分钟',
        onPressed: onResumeLessonDialogue,
      );
    }
    if (state.reviewIsPrimary) {
      final count = state.dueReviewCount;
      return _TodayTask(
        label: '今日复习',
        title: '先复习 $count 项',
        note: state.reviewBacklog
            ? '有积压项目；先花几分钟清掉到期复习，再开启新课。'
            : '之前练过的关键句，今天换个情境再用一次。',
        action: '开始复习',
        minutes: '${(count * 2).clamp(2, 10)} 分钟',
        onPressed: onStartReview,
      );
    }
    // A0 课程学完、尚未通过阶段评估时，先巩固再评估；通过后回到下一课。
    if (state.a0LessonsComplete && !state.a0Passed) return _stageTask();

    if (state.allLessonsComplete) {
      return _TodayTask(
        label: '已学完',
        title: '所有课程已完成',
        note: '你已学完全部课程内容！建议保持日常到期复习或自由情境对话。',
        action: '去复习',
        minutes: '10 分钟',
        onPressed: onStartReview,
      );
    }

    final segments = lesson.segments.length;
    final segmentIndex = state.activeSegmentIndexFor(lesson.id);
    final segment = segmentIndex + 1;
    final isSegmentResuming = segments > 1 && segmentIndex > 0;

    return _TodayTask(
      label: isSegmentResuming ? '继续课程' : '今日新课',
      title:
          '第 ${lesson.number} 课 · ${lesson.title}'
          '${segments > 1 ? ' · 第 $segment/$segments 段' : ''}',
      note: isSegmentResuming
          ? '第 $segmentIndex 段已学完；继续本课下一段情境训练。'
          : '预热词汇 → 听说读写 → 对话 → 独立尝试',
      action: isSegmentResuming ? '继续学习第 $segment 段' : '开始今天的学习',
      minutes: '12 分钟',
      onPressed: () {
        if (state.activeLessonId != lesson.id) {
          state.openLesson(lesson.id);
        }
        onStartLesson();
      },
    );
  }

  _TodayTask _stageTask() {
    final usable =
        '可使用 ${state.coreUsableCount}/$a0UsableGoal · '
        '已掌握 ${state.coreMasteredCount}/$a0MasteredGoal';
    final packId = state.nextAssessmentPackId;
    if (state.a0AssessmentReady && packId != null) {
      return _TodayTask(
        label: '阶段评估',
        title: 'A0 阶段评估 · $packId',
        note: '$usable。可以开始阶段评估，两套评估间隔至少 24 小时。',
        action: '开始阶段评估',
        minutes: '15 分钟',
        onPressed: () => onOpenAssessment(packId),
      );
    }
    return _TodayTask(
      label: 'A0 巩固',
      title: state.a0AssessmentReady ? '第二套评估 24 小时后开放' : 'A0 课程已学完',
      note: state.a0AssessmentReady
          ? '第一套评估已通过。等待期间继续巩固。'
          : '$usable。继续按时复习、做情境对话，达到要求后开放阶段评估。',
      action: '安排一题巩固练习',
      minutes: '3 分钟',
      onPressed: onStartReinforcement,
    );
  }
}

class _TodayTask {
  const _TodayTask({
    required this.label,
    required this.title,
    required this.note,
    required this.action,
    required this.minutes,
    required this.onPressed,
  });
  final String label;
  final String title;
  final String note;
  final String action;
  final String minutes;
  final VoidCallback onPressed;
}