import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:package_info_plus/package_info_plus.dart';
import 'package:riverpod_annotation/riverpod_annotation.dart';

part 'main.g.dart';

void main() {
  runApp(ProviderScope(child: const MainApp()));
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomeScreen(),
      builder: (context, child) {
        return AppStartupWidget(onLoaded: (context) => child!);
      },
    );
  }
}

@riverpod
class AppStartupNotifier extends _$AppStartupNotifier {
  @override
  Future<void> build() async {
    await Future.delayed(Duration(seconds: 2));
    await ref.watch(packageInfoProvider.future);
  }
}

class AppStartupWidget extends ConsumerWidget {
  const AppStartupWidget({super.key, required this.onLoaded});
  final WidgetBuilder onLoaded;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    // 1. eagerly initialize appStartupProvider (and all the providers it depends on)
    final appStartupState = ref.watch(appStartupProvider);
    return appStartupState.when(
      // 2. loading state
      loading: () {
        return Scaffold(
          appBar: AppBar(),
          body: Center(child: CircularProgressIndicator()),
        );
      },
      // 3. error state
      error: (e, st) {
        return Scaffold(
          appBar: AppBar(),
          body: Center(child: Text('Loading Error: $e')),
        );
      },
      // 5. success - now load the main app
      data: (success) {
        return onLoaded(context);
      },
    );
  }
}

@Riverpod(keepAlive: true)
Future<PackageInfo> packageInfo(Ref ref) {
  return PackageInfo.fromPlatform();
}

class HomeScreen extends ConsumerWidget {
  const HomeScreen({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final packageInfo = ref.watch(packageInfoProvider).requireValue;
    return Scaffold(
      appBar: AppBar(title: Text(packageInfo.appName)),
      body: Center(
        child: Text('${packageInfo.appName} ${packageInfo.version}'),
      ),
    );
  }
}