Problem: How to use GoRouter and Flutter Adaptive Scaffold

main.dart

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

final router =
    GoRouter(initialLocation: '/', debugLogDiagnostics: true, routes: [
  GoRoute(
    path: '/',
    builder: (context, state) => const AppScreen(primaryBody: Placeholder()),
  ),
  ShellRoute(
      builder: (context, state, child) {
        return AppScreen(
          primaryBody: child,
          // secondaryBody: secondary, ???
        );
      },
      routes: [
        GoRoute(
            path: '/main1',
            builder: (context, state) => const PrimaryBody(type: 'main1'),
            routes: [
              GoRoute(
                path: 'details/:id',
                builder: (context, state) =>
                    SecondaryBody(id: state.pathParameters['id']!),
              )
            ]),
        GoRoute(
            path: '/main2',
            builder: (context, state) => const PrimaryBody(type: 'main2'),
            routes: [
              GoRoute(
                path: 'details/:id',
                builder: (context, state) =>
                    SecondaryBody(id: state.pathParameters['id']!),
              )
            ]),
      ])
]);

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      title: 'GoRouter with Adaptive Scaffold',
      routerConfig: router,
    );
  }
}

class AppScreen extends StatelessWidget {
  const AppScreen({super.key, required this.primaryBody, this.secondaryBody});

  final Widget primaryBody;
  final Widget? secondaryBody;

  @override
  Widget build(BuildContext context) {
    return AdaptiveScaffold(
      selectedIndex: _calculateSelectedIndex(context),
      onSelectedIndexChange: (newIndex) {
        context.go('/main${newIndex + 1}');
      },
      destinations: const [
        NavigationDestination(
          icon: Icon(Icons.inbox_outlined),
          selectedIcon: Icon(Icons.inbox),
          label: 'Main 1',
        ),
        NavigationDestination(
          icon: Icon(Icons.article_outlined),
          selectedIcon: Icon(Icons.article),
          label: 'Main 2',
        ),
      ],
      body: (_) => primaryBody,
      secondaryBody: secondaryBody != null ? (_) => secondaryBody! : null,
    );
  }

  int? _calculateSelectedIndex(BuildContext context) {
    return switch (GoRouterState.of(context).uri.toString()) {
      '/main1' => 0,
      '/main2' => 1,
      _ => null,
    };
  }
}

class PrimaryBody extends StatelessWidget {
  const PrimaryBody({super.key, required this.type});

  final String type;

  @override
  Widget build(BuildContext context) {
    return ListView.builder(
      itemCount: 10,
      itemBuilder: (context, index) => Padding(
          padding: const EdgeInsets.all(20),
          child: ElevatedButton(
            child: Text('Element $index ($type)'),
            onPressed: () {
              context.go('/$type/details/$index');
            },
          )),
    );
  }
}

class SecondaryBody extends StatelessWidget {
  const SecondaryBody({super.key, required this.id});

  final String id;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Text("Element $id details"),
    );
  }
}