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

/// 按 BuildContext 缓存 token：同 State 多次 build 复用同一 token，
/// 新 State（context 对象不同）自动分配新 token，确保 onBack 闭包不被旧 State 覆盖
final Expando<int> _contextToken = Expando<int>();
int _globalNavToken = 0;

int _tokenForContext(BuildContext context) =>
    _contextToken[context] ??= ++_globalNavToken;

/// NavBar 配置，由各页面在 build 中设置，AppShell 统一渲染
class NavBarConfig {
  final String title;
  final bool showBack;
  final bool showRight;
  final Widget? rightWidget;
  final VoidCallback? onBack;
  final IconData? leadingIcon;
  final bool hasFilter;
  final int filterVersion;
  /// 页面实例标识：每个 State 实例生成唯一 token，确保新 State 的 onBack 闭包不被
  /// 旧 State 的 config（值相等但闭包指向已销毁 State）覆盖
  final int? token;

  const NavBarConfig({
    required this.title,
    this.showBack = false,
    this.showRight = false,
    this.rightWidget,
    this.onBack,
    this.leadingIcon,
    this.hasFilter = false,
    this.filterVersion = 0,
    this.token,
  });

  /// 根页面默认配置（无返回按钮）
  static const home = NavBarConfig(title: 'TBOSS 工作台', showBack: false);
  static const messages = NavBarConfig(title: '消息', showBack: false);
  static const profile = NavBarConfig(title: '我的', showBack: false);

  /// 带返回按钮的页面快捷构造
  factory NavBarConfig.withBack(String title, {VoidCallback? onBack}) {
    return NavBarConfig(title: title, showBack: true, onBack: onBack);
  }

  /// 带返回按钮 + 右侧按钮的页面快捷构造
  factory NavBarConfig.withRight(
    String title, {
    required Widget rightWidget,
    VoidCallback? onBack,
  }) {
    return NavBarConfig(
      title: title,
      showBack: true,
      showRight: true,
      rightWidget: rightWidget,
      onBack: onBack,
    );
  }

  @override
  bool operator ==(Object other) =>
      other is NavBarConfig &&
      other.title == title &&
      other.showBack == showBack &&
      other.showRight == showRight &&
      other.hasFilter == hasFilter &&
      other.filterVersion == filterVersion &&
      other.token == token;
  // token 确保不同 State 实例的 config 不相等，onBack/rightWidget 通过 token 间接区分

  @override
  int get hashCode =>
      Object.hash(title, showBack, showRight, hasFilter, filterVersion, token);
}

/// NavBar 配置变更器，内部做相等判断避免无限重建
///
/// 通过 [Future.microtask] 将状态更新推迟到事件循环下一个 tick，
/// 避免子页面在 build 中更新 provider 时与 AppShell watch 冲突。
class NavBarConfigNotifier extends StateNotifier<NavBarConfig> {
  NavBarConfigNotifier() : super(NavBarConfig.home);

  void update(NavBarConfig config) {
    if (state != config) {
      Future.microtask(() {
        if (mounted) state = config;
      });
    }
  }
}

/// NavBar 配置的 Provider —— 各页面在 build 中更新，AppShell 统一消费
final navBarConfigProvider =
    StateNotifierProvider<NavBarConfigNotifier, NavBarConfig>(
      (ref) => NavBarConfigNotifier(),
    );

/// 更新导航栏配置。使用 GoRouter 判断当前页面是否为可见路由：
/// - 页面自身的 GoRouterState.uri == GoRouter 注册的当前 uri → 允许更新
/// - 不匹配 → 被覆盖的旧页面（GoRouter 级联重建导致），跳过
///
/// 此方法替代了 ModalRoute.isCurrent，因为缓存引擎下旧路由残留会导致
/// ModalRoute 误判；GoRouter 的状态不受 Widget 树生命周期影响，结果更可靠。
void setNavBarTitle(BuildContext context, WidgetRef ref, NavBarConfig config) {
  try {
    final pageUri = GoRouterState.of(context).uri.toString();
    final currentUri = GoRouter.of(context).state.uri.toString();
    if (pageUri != currentUri) return;
  } catch (_) {
    // GoRouter 不可用时直接放行
  }
  // 注入 context 绑定的 token：同 State 多次 build 共享，换 State 自动换新 token
  final token = _tokenForContext(context);
  final effective = config.token != null ? config : NavBarConfig(
    title: config.title,
    showBack: config.showBack,
    showRight: config.showRight,
    rightWidget: config.rightWidget,
    onBack: config.onBack,
    leadingIcon: config.leadingIcon,
    hasFilter: config.hasFilter,
    filterVersion: config.filterVersion,
    token: token,
  );
  ref.read(navBarConfigProvider.notifier).update(effective);
}