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/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/about/about_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.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(),
      ),
      ShellRoute(
        builder: (context, state, child) => AppShell(child: child),
        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']!)))),
          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']!)))),
          GoRoute(
              path: '/inventory',
              pageBuilder: (_, __) =>
                  _noTransition(const InventoryListScreen())),
          GoRoute(
              path: '/inventory/check',
              pageBuilder: (_, __) =>
                  _noTransition(const InventoryCheckScreen())),
          GoRoute(
              path: '/partners',
              pageBuilder: (_, __) => _noTransition(const PartnersScreen())),
          GoRoute(
              path: '/finance',
              pageBuilder: (_, __) => _noTransition(const FinanceScreen())),
          GoRoute(
              path: '/products',
              pageBuilder: (_, __) => _noTransition(const ProductsScreen())),
          GoRoute(
              path: '/products/:id',
              pageBuilder: (_, state) => _noTransition(ProductDetailScreen(
                  productId: int.parse(state.pathParameters['id']!)))),
          GoRoute(
              path: '/settings',
              pageBuilder: (_, __) => _noTransition(const SettingsScreen())),
          GoRoute(
              path: '/about',
              pageBuilder: (_, __) => _noTransition(const AboutScreen())),
        ],
      ),
    ],
  );

  ref.onDispose(router.dispose);

  return router;
});