import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:go_router/go_router.dart';
import '../../screens/auth/login_screen.dart';
import '../../screens/auth/register_screen.dart';
import '../../screens/shell/app_shell.dart';
import '../../screens/stock_in/stock_in_list_screen.dart';
import '../../screens/stock_in/stock_in_form_screen.dart';
import '../../screens/stock_out/stock_out_list_screen.dart';
import '../../screens/stock_out/stock_out_form_screen.dart';
import '../../screens/inventory/inventory_list_screen.dart';
import '../../screens/inventory/inventory_check_screen.dart';
import '../../screens/partners/partners_screen.dart';
import '../../screens/finance/finance_screen.dart';
import '../../screens/products/products_screen.dart';
import '../../screens/products/product_detail_screen.dart';
import '../../screens/public/public_product_screen.dart';
import '../../screens/public/public_shop_products_screen.dart';
import '../../screens/settings/settings_screen.dart';
import '../../screens/settings/users_screen.dart';
import '../../screens/about/about_screen.dart';
import '../../screens/devices/device_management_screen.dart';
import '../auth/auth_state.dart';

Page<void> _noTransition(Widget child) => NoTransitionPage<void>(child: child);

/// ChangeNotifier that bridges Riverpod auth state → GoRouter refreshListenable.
class _RouterNotifier extends ChangeNotifier {
  final Ref _ref;

  _RouterNotifier(this._ref) {
    _ref.listen<AuthState>(authStateProvider, (prev, next) {
      debugPrint('[Router] authState changed:'
          ' initialized=${next.initialized}'
          ' isLoggedIn=${next.isLoggedIn}'
          ' user=${next.user?.username}');
      notifyListeners();
    });
  }

  String? redirect(BuildContext context, GoRouterState state) {
    final authState = _ref.read(authStateProvider);
    final isLoggedIn = authState.isLoggedIn;
    final loc = state.matchedLocation;
    final isPublicRoute = loc == '/login' ||
        loc == '/register' ||
        loc.startsWith('/product/') ||
        loc.startsWith('/shop/');
    final result = !authState.initialized
        ? null
        : (!isLoggedIn && !isPublicRoute)
            ? '/login'
            : (isLoggedIn && loc == '/login')
                ? '/stock-in'
                : null;
    debugPrint('[Router] redirect: location=$loc'
        ' initialized=${authState.initialized}'
        ' isLoggedIn=$isLoggedIn'
        ' → ${result ?? "null (no redirect)"}');
    return result;
  }
}

/// Separate provider so that appRouterProvider has NO dependencies and
/// is never rebuilt when auth state changes (prevents router reset to /login).
final _routerNotifierProvider = Provider<_RouterNotifier>((ref) {
  final notifier = _RouterNotifier(ref);
  ref.onDispose(notifier.dispose);
  return notifier;
});

final appRouterProvider = Provider<GoRouter>((ref) {
  // Use ref.read (not ref.watch) so appRouterProvider never rebuilds on auth change.
  final notifier = ref.read(_routerNotifierProvider);

  final router = GoRouter(
    initialLocation: '/login',
    refreshListenable: notifier,
    redirect: notifier.redirect,
    routes: [
      // Public product scan — no auth, no shell nav bar
      GoRoute(
        path: '/product/:public_id',
        builder: (context, state) =>
            PublicProductScreen(publicId: state.pathParameters['public_id']!),
      ),
      // Public shop product list — no auth, no shell nav bar
      GoRoute(
        path: '/shop/:shop_code',
        builder: (context, state) => PublicShopProductsScreen(
          shopCode: state.pathParameters['shop_code']!,
          shopName: state.uri.queryParameters['shopName'] ?? '',
        ),
      ),
      GoRoute(
        path: '/login',
        builder: (context, state) => const LoginScreen(),
      ),
      GoRoute(
        path: '/register',
        builder: (context, state) => const RegisterScreen(),
      ),
      // 各栏目拆为独立分支：StatefulShellRoute.indexedStack 让每个分支的 Navigator
      // 及其页面 State 常驻，跨栏目切换不再销毁上一页（半填表单/内部 tab/滚动位置保活）。
      // 分支顺序必须与 AppShell._navItems 一致（navigationShell.currentIndex 据此高亮）。
      StatefulShellRoute.indexedStack(
        builder: (context, state, navigationShell) =>
            AppShell(navigationShell: navigationShell),
        branches: [
          // 0 入库管理
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/stock-in',
                pageBuilder: (_, __) =>
                    _noTransition(const StockInListScreen())),
            GoRoute(
                path: '/stock-in/new',
                pageBuilder: (_, __) =>
                    _noTransition(const StockInFormScreen())),
            GoRoute(
                path: '/stock-in/edit/:id',
                pageBuilder: (_, state) => _noTransition(StockInFormScreen(
                    editOrderId: int.parse(state.pathParameters['id']!)))),
          ]),
          // 1 出库管理
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/stock-out',
                pageBuilder: (_, __) =>
                    _noTransition(const StockOutListScreen())),
            GoRoute(
                path: '/stock-out/new',
                pageBuilder: (_, __) =>
                    _noTransition(const StockOutFormScreen())),
            GoRoute(
                path: '/stock-out/edit/:id',
                pageBuilder: (_, state) => _noTransition(StockOutFormScreen(
                    editOrderId: int.parse(state.pathParameters['id']!)))),
          ]),
          // 2 库存管理
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/inventory',
                pageBuilder: (_, __) =>
                    _noTransition(const InventoryListScreen())),
            GoRoute(
                path: '/inventory/check',
                pageBuilder: (_, __) =>
                    _noTransition(const InventoryCheckScreen())),
          ]),
          // 3 财务管理
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/finance',
                pageBuilder: (_, __) => _noTransition(const FinanceScreen())),
          ]),
          // 4 往来单位
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/partners',
                pageBuilder: (_, __) => _noTransition(const PartnersScreen())),
          ]),
          // 5 基础数据
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/products',
                // ?tab=intro → 商品介绍 tab（对齐原型 products.html?tab=intro）
                pageBuilder: (_, state) => _noTransition(ProductsScreen(
                    initialTab:
                        state.uri.queryParameters['tab'] == 'intro' ? 1 : 0))),
            GoRoute(
                path: '/products/:id',
                pageBuilder: (_, state) => _noTransition(ProductDetailScreen(
                    productId: int.parse(state.pathParameters['id']!)))),
          ]),
          // 6 设备管理
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/devices',
                pageBuilder: (_, __) =>
                    _noTransition(const DeviceManagementScreen())),
          ]),
          // 7 系统设置（面板：门店信息/用户管理/编号规则/授权兑换券/偏好设置）
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/settings',
                pageBuilder: (_, state) {
                  const tabIndex = {
                    'shop': 0,
                    'users': 1,
                    'number': 2,
                    'license': 3,
                    'pref': 4,
                  };
                  final tab = tabIndex[state.uri.queryParameters['tab']] ?? 0;
                  return _noTransition(SettingsScreen(initialTab: tab));
                }),
            // 用户管理独立页（照原型 users.html）
            GoRoute(
                path: '/settings/users',
                pageBuilder: (_, __) => _noTransition(const UsersScreen())),
          ]),
          // 8 关于我们
          StatefulShellBranch(routes: [
            GoRoute(
                path: '/about',
                pageBuilder: (_, __) => _noTransition(const AboutScreen())),
          ]),
        ],
      ),
    ],
  );

  ref.onDispose(router.dispose);

  return router;
});