import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../core/theme/app_theme.dart';
import '../../providers/feed_provider.dart';
import '../../screens/category/category_screen.dart';
import '../../screens/feed/feed_screen.dart';
import '../../screens/notification/notifications_screen.dart';
import '../../screens/profile/mine_screen.dart';
import '../../screens/upload/upload_screen.dart';

/// 首页壳：底部 Tab（首页/分类/发布/消息/我的），02-技术文档信息架构
/// IndexedStack 保活各 Tab 状态（Feed 播放器池 / 分类滚动位置 / 上传流程不被销毁）
class HomeShell extends ConsumerStatefulWidget {
  const HomeShell({super.key});

  @override
  ConsumerState<HomeShell> createState() => _HomeShellState();
}

class _HomeShellState extends ConsumerState<HomeShell> {
  int _index = 0;

  /// Feed 三种策略的 provider keys（切 Tab 时用于暂停/恢复播放器池）
  static const _feedStrategies = FeedStrategy.values;

  void _onTabSelected(int i) {
    if (i == _index) return;
    // 切到非首页：挂起所有 Feed 策略池——suspend 记录断点后 stop 全槽位
    // （mpv pause 停不住 HLS 预读，只有 stop 能可靠断下载）；
    // 回首页 rebind 重新 open + seek 断点续播，缓存分片零流量（抖音行为）
    if (i != 0) {
      for (final s in _feedStrategies) {
        ref.read(feedProvider(s).notifier).pool.suspend();
      }
    }
    ref.read(feedTabVisibleProvider.notifier).state = i == 0;
    setState(() => _index = i);
    // 切回首页：只恢复当前选中策略的池（其余保持挂起）
    if (i == 0) {
      final active = ref.read(activeFeedStrategyProvider);
      final notifier = ref.read(feedProvider(active).notifier);
      unawaited(() async {
        await notifier.pool.resume();
        // 兜底：挂起期间首屏 bind 可能尚未发生，补一次当前页绑定播放
        await notifier.rebindCurrent();
      }());
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: IndexedStack(
        index: _index,
        children: const [
          FeedScreen(),
          CategoryScreen(),
          UploadScreen(),
          NotificationsScreen(),
          MineScreen(),
        ],
      ),
      bottomNavigationBar: NavigationBar(
        height: 60,
        backgroundColor: AppColors.surface,
        indicatorColor: AppColors.primary.withValues(alpha: 0.2),
        selectedIndex: _index,
        onDestinationSelected: _onTabSelected,
        destinations: const [
          NavigationDestination(
            icon: Icon(Icons.home_outlined),
            selectedIcon: Icon(Icons.home, color: AppColors.primary),
            label: '首页',
          ),
          NavigationDestination(
            icon: Icon(Icons.grid_view_outlined),
            label: '分类',
          ),
          NavigationDestination(
            icon: Icon(Icons.add_box_outlined),
            label: '发布',
          ),
          NavigationDestination(
            icon: Icon(Icons.notifications_none),
            label: '消息',
          ),
          NavigationDestination(
            icon: Icon(Icons.person_outline),
            label: '我的',
          ),
        ],
      ),
    );
  }
}