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

/// Verifies that re-tapping the active bottom navigation tab pops any
/// Navigator-pushed sub-screens back to the branch root.
///
/// This exercises the same pattern used by [MainShellScreen]: each
/// [StatefulShellBranch] has a [GlobalKey<NavigatorState>] and the shell
/// calls `popUntil((route) => route.isFirst)` when the active tab is
/// tapped again.
void main() {
  group('Bottom navigation tab re-tap', () {
    late GlobalKey<NavigatorState> homeNavKey;
    late GlobalKey<NavigatorState> settingsNavKey;
    late GoRouter router;

    setUp(() {
      homeNavKey = GlobalKey<NavigatorState>(debugLabel: 'home');
      settingsNavKey = GlobalKey<NavigatorState>(debugLabel: 'settings');

      router = GoRouter(
        initialLocation: '/home',
        routes: [
          StatefulShellRoute.indexedStack(
            builder: (context, state, shell) {
              return _TestShell(
                navigationShell: shell,
                branchNavigatorKeys: [homeNavKey, settingsNavKey],
              );
            },
            branches: [
              // Branch 0: Home (dummy, needed to satisfy >= 2 destinations)
              StatefulShellBranch(
                navigatorKey: homeNavKey,
                routes: [
                  GoRoute(
                    path: '/home',
                    builder: (context, state) => const Scaffold(
                      body: Center(child: Text('Home')),
                    ),
                  ),
                ],
              ),
              // Branch 1: Settings
              StatefulShellBranch(
                navigatorKey: settingsNavKey,
                routes: [
                  GoRoute(
                    path: '/settings',
                    builder: (context, state) => const _SettingsMainScreen(),
                  ),
                ],
              ),
            ],
          ),
        ],
      );
    });

    tearDown(() {
      router.dispose();
    });

    testWidgets(
      'tapping active tab pops Navigator-pushed sub-screen to root',
      (tester) async {
        await tester.pumpWidget(MaterialApp.router(routerConfig: router));
        await tester.pumpAndSettle();

        // Navigate to Settings tab.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        // Main settings screen is visible.
        expect(find.text('Settings Main'), findsOneWidget);
        expect(find.text('Sub Settings'), findsNothing);

        // Push a sub-settings screen via Navigator (same as the real app).
        await tester.tap(find.text('Open Sub-Settings'));
        await tester.pumpAndSettle();

        // Sub-settings screen is now visible; main is not.
        expect(find.text('Sub Settings'), findsOneWidget);
        expect(find.text('Settings Main'), findsNothing);

        // Re-tap the Settings tab in the bottom navigation.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        // We should be back at the main settings screen.
        expect(find.text('Settings Main'), findsOneWidget);
        expect(find.text('Sub Settings'), findsNothing);
      },
    );

    testWidgets(
      'tapping active tab when already at root is a no-op',
      (tester) async {
        await tester.pumpWidget(MaterialApp.router(routerConfig: router));
        await tester.pumpAndSettle();

        // Navigate to Settings tab.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        expect(find.text('Settings Main'), findsOneWidget);

        // Re-tap the already-active tab without pushing any sub-screen.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        // Still on the main settings screen.
        expect(find.text('Settings Main'), findsOneWidget);
      },
    );

    testWidgets(
      'tapping active tab pops multiple stacked sub-screens',
      (tester) async {
        await tester.pumpWidget(MaterialApp.router(routerConfig: router));
        await tester.pumpAndSettle();

        // Navigate to Settings tab.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        // Push first sub-screen.
        await tester.tap(find.text('Open Sub-Settings'));
        await tester.pumpAndSettle();
        expect(find.text('Sub Settings'), findsOneWidget);

        // Push a second sub-screen on top.
        await tester.tap(find.text('Go Deeper'));
        await tester.pumpAndSettle();
        expect(find.text('Deep Settings'), findsOneWidget);

        // Re-tap the tab — should pop all the way back to root.
        await tester.tap(find.text('Settings'));
        await tester.pumpAndSettle();

        expect(find.text('Settings Main'), findsOneWidget);
        expect(find.text('Sub Settings'), findsNothing);
        expect(find.text('Deep Settings'), findsNothing);
      },
    );
  });
}

// ---------------------------------------------------------------------------
// Test helper widgets
// ---------------------------------------------------------------------------

/// Minimal shell that replicates [MainShellScreen]'s re-tap behavior.
class _TestShell extends StatelessWidget {
  final StatefulNavigationShell navigationShell;
  final List<GlobalKey<NavigatorState>> branchNavigatorKeys;

  const _TestShell({
    required this.navigationShell,
    required this.branchNavigatorKeys,
  });

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: navigationShell,
      bottomNavigationBar: NavigationBar(
        selectedIndex: navigationShell.currentIndex,
        onDestinationSelected: (index) {
          // Same logic as MainShellScreen._onDestinationSelected
          if (index == navigationShell.currentIndex) {
            final navigatorKey = branchNavigatorKeys[index];
            navigatorKey.currentState?.popUntil((route) => route.isFirst);
          }
          navigationShell.goBranch(
            index,
            initialLocation: index == navigationShell.currentIndex,
          );
        },
        destinations: const [
          NavigationDestination(
            icon: Icon(Icons.home),
            label: 'Home',
          ),
          NavigationDestination(
            icon: Icon(Icons.settings),
            label: 'Settings',
          ),
        ],
      ),
    );
  }
}

/// Main settings screen with a button to push a sub-screen.
class _SettingsMainScreen extends StatelessWidget {
  const _SettingsMainScreen();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Text('Settings Main'),
            ElevatedButton(
              onPressed: () {
                Navigator.of(context).push(
                  MaterialPageRoute(
                    builder: (_) => const _SubSettingsScreen(),
                  ),
                );
              },
              child: const Text('Open Sub-Settings'),
            ),
          ],
        ),
      ),
    );
  }
}

/// Sub-settings screen pushed via Navigator (like AppearanceSettingsScreen).
class _SubSettingsScreen extends StatelessWidget {
  const _SubSettingsScreen();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            const Text('Sub Settings'),
            ElevatedButton(
              onPressed: () {
                Navigator.of(context).push(
                  MaterialPageRoute(
                    builder: (_) => const _DeepSettingsScreen(),
                  ),
                );
              },
              child: const Text('Go Deeper'),
            ),
          ],
        ),
      ),
    );
  }
}

/// A second level sub-screen for testing multi-level pop.
class _DeepSettingsScreen extends StatelessWidget {
  const _DeepSettingsScreen();

  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: Center(child: Text('Deep Settings')),
    );
  }
}