import 'package:flutter/material.dart';

import '../models/study_plan.dart';

/// 学习首页。
///
/// 信息层级刻意保持简单，和百词斩首页同构：
///   当前材料 → 今日任务（要做什么 + 要多久）→ 唯一主行动 → 快捷入口。
/// 但去掉它的商业化部分：没有广告位、没有课程倒计时、没有电商入口。
class StudyPage extends StatelessWidget {
  const StudyPage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('学习')),
      body: ListView(
        padding: const EdgeInsets.fromLTRB(16, 8, 16, 32),
        children: const <Widget>[
          _DeckCard(plan: StudyPlan.sample),
          SizedBox(height: 14),
          _TodayPlanCard(plan: StudyPlan.sample),
          SizedBox(height: 18),
          _QuickActions(),
        ],
      ),
    );
  }
}

/// 当前单元集：名称、算法、完成度。
class _DeckCard extends StatelessWidget {
  const _DeckCard({required this.plan});

  final StudyPlan plan;

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    final ColorScheme colors = theme.colorScheme;
    final TextTheme text = theme.textTheme;

    return _SurfaceCard(
      onTap: () => _pending(context, '单元集切换'),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Row(
            children: <Widget>[
              Container(
                width: 48,
                height: 48,
                decoration: BoxDecoration(
                  color: colors.primaryContainer,
                  borderRadius: BorderRadius.circular(12),
                ),
                child: Icon(
                  Icons.menu_book_rounded,
                  color: colors.onPrimaryContainer,
                ),
              ),
              const SizedBox(width: 12),
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Text(
                      plan.deckName,
                      style: text.titleMedium,
                      maxLines: 1,
                      overflow: TextOverflow.ellipsis,
                    ),
                    const SizedBox(height: 2),
                    Text(
                      '调度算法 ${plan.algorithm}',
                      style: text.bodySmall?.copyWith(
                        color: colors.onSurfaceVariant,
                      ),
                    ),
                  ],
                ),
              ),
              Icon(
                Icons.unfold_more_rounded,
                size: 20,
                color: colors.onSurfaceVariant,
              ),
            ],
          ),
          const SizedBox(height: 16),
          ClipRRect(
            borderRadius: BorderRadius.circular(6),
            child: LinearProgressIndicator(
              value: plan.progress,
              minHeight: 8,
              backgroundColor: colors.surfaceContainerHighest,
            ),
          ),
          const SizedBox(height: 8),
          Row(
            children: <Widget>[
              Text(
                '${plan.activatedItems} / ${plan.totalItems}',
                style: text.bodySmall?.copyWith(color: colors.onSurfaceVariant),
              ),
              const Spacer(),
              Text(
                plan.progressPercent,
                style: text.bodySmall?.copyWith(
                  color: colors.onSurfaceVariant,
                  fontWeight: FontWeight.w600,
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

/// 今日任务：两个数字 + 时长承诺 + 唯一主行动。
class _TodayPlanCard extends StatelessWidget {
  const _TodayPlanCard({required this.plan});

  final StudyPlan plan;

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    final ColorScheme colors = theme.colorScheme;
    final TextTheme text = theme.textTheme;

    return _SurfaceCard(
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Text('今日计划', style: text.titleMedium),
          const SizedBox(height: 18),
          Row(
            children: <Widget>[
              Expanded(child: _BigStat(label: '待复习', value: plan.dueItems)),
              Expanded(child: _BigStat(label: '待新识', value: plan.newItems)),
            ],
          ),
          const SizedBox(height: 16),
          Center(
            child: Row(
              mainAxisSize: MainAxisSize.min,
              children: <Widget>[
                Icon(
                  Icons.schedule_rounded,
                  size: 16,
                  color: colors.onSurfaceVariant,
                ),
                const SizedBox(width: 6),
                Text(
                  plan.estimatedLabel,
                  style: text.bodyMedium?.copyWith(
                    color: colors.onSurfaceVariant,
                  ),
                ),
              ],
            ),
          ),
          const SizedBox(height: 16),
          FilledButton(
            onPressed: plan.isEmpty ? null : () => _pending(context, '学习会话'),
            style: FilledButton.styleFrom(
              minimumSize: const Size.fromHeight(52),
              textStyle: text.titleMedium,
            ),
            child: Text(plan.isEmpty ? '今天已完成' : '开始学习'),
          ),
        ],
      ),
    );
  }
}

class _BigStat extends StatelessWidget {
  const _BigStat({required this.label, required this.value});

  final String label;
  final int value;

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    final ColorScheme colors = theme.colorScheme;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Text(
          label,
          style: theme.textTheme.bodyMedium?.copyWith(
            color: colors.onSurfaceVariant,
          ),
        ),
        const SizedBox(height: 2),
        Row(
          crossAxisAlignment: CrossAxisAlignment.baseline,
          textBaseline: TextBaseline.alphabetic,
          children: <Widget>[
            Text(
              '$value',
              style: theme.textTheme.displaySmall?.copyWith(
                fontWeight: FontWeight.w700,
                height: 1.1,
              ),
            ),
            const SizedBox(width: 6),
            Text(
              '条',
              style: theme.textTheme.bodySmall?.copyWith(
                color: colors.onSurfaceVariant,
              ),
            ),
          ],
        ),
      ],
    );
  }
}

/// 快捷入口。都是「学习域」内的次级入口，维护类操作不放这里。
class _QuickActions extends StatelessWidget {
  const _QuickActions();

  static const List<(IconData, String)> _items = <(IconData, String)>[
    (Icons.star_border_rounded, '收藏夹'),
    (Icons.volume_up_outlined, '语音缓存'),
    (Icons.history_rounded, '最近学习'),
    (Icons.replay_rounded, '难点重练'),
  ];

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    final ColorScheme colors = theme.colorScheme;

    return Row(
      children: <Widget>[
        for (final (int index, (IconData icon, String label)) in _items.indexed)
          Expanded(
            child: Padding(
              padding: EdgeInsets.only(left: index == 0 ? 0 : 8),
              child: Material(
                color: colors.surfaceContainerLow,
                borderRadius: BorderRadius.circular(16),
                child: InkWell(
                  borderRadius: BorderRadius.circular(16),
                  onTap: () => _pending(context, label),
                  child: Padding(
                    padding: const EdgeInsets.symmetric(vertical: 14),
                    child: Column(
                      children: <Widget>[
                        Icon(icon, size: 22, color: colors.primary),
                        const SizedBox(height: 8),
                        Text(
                          label,
                          style: theme.textTheme.labelSmall?.copyWith(
                            color: colors.onSurfaceVariant,
                          ),
                          maxLines: 1,
                          overflow: TextOverflow.ellipsis,
                        ),
                      ],
                    ),
                  ),
                ),
              ),
            ),
          ),
      ],
    );
  }
}

/// 统一的卡片外观，避免每处重复写圆角和底色。
class _SurfaceCard extends StatelessWidget {
  const _SurfaceCard({required this.child, this.onTap});

  final Widget child;

  /// 可点击时给出水波纹反馈；为 null 时是纯展示卡片。
  final VoidCallback? onTap;

  @override
  Widget build(BuildContext context) {
    final BorderRadius radius = BorderRadius.circular(20);
    return Material(
      color: Theme.of(context).colorScheme.surfaceContainerLow,
      borderRadius: radius,
      clipBehavior: Clip.antiAlias,
      child: InkWell(
        onTap: onTap,
        borderRadius: radius,
        child: Padding(padding: const EdgeInsets.all(18), child: child),
      ),
    );
  }
}

/// 尚未接入内核的入口，点击给出明确反馈而不是静默无响应。
void _pending(BuildContext context, String feature) {
  ScaffoldMessenger.of(context).showSnackBar(
    SnackBar(
      content: Text('$feature 尚未接入内核'),
      behavior: SnackBarBehavior.floating,
      margin: const EdgeInsets.fromLTRB(16, 0, 16, 88),
    ),
  );
}