import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

import 'screens/main_shell.dart';
import 'screens/user_agreement_screen.dart';
import 'services/app_state.dart';
import 'theme/app_theme.dart';
import 'widgets/ad_free_upsell_dialog.dart';

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

/// A stable handle on the navigator so [AppState.onAdWatched] can show the
/// "remove ads" dialog from wherever the app happens to be — it fires from
/// deep inside a background sync, not from a widget's own build method, so
/// there's no local [BuildContext] to reach for at that point.
final navigatorKey = GlobalKey<NavigatorState>();

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

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (_) => AppState()..init(),
      child: Consumer<AppState>(
        builder: (context, appState, _) {
          appState.onAdWatched ??= () {
            final dialogContext = navigatorKey.currentContext;
            if (dialogContext != null) showAdFreeUpsellDialog(dialogContext);
          };
          return MaterialApp(
            navigatorKey: navigatorKey,
            title: 'Fuel Tax Tracker',
            theme: AppTheme.light,
            darkTheme: AppTheme.dark,
            themeMode: appState.themeMode,
            home: const AppRoot(),
          );
        },
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Consumer<AppState>(
      builder: (context, appState, _) {
        if (appState.isLoading) {
          return const Scaffold(
            body: Center(child: CircularProgressIndicator()),
          );
        }
        if (appState.initError != null) {
          return Scaffold(
            body: Center(
              child: Padding(
                padding: const EdgeInsets.all(24),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    Icon(Icons.error_outline,
                        size: 48, color: Theme.of(context).colorScheme.error),
                    const SizedBox(height: 16),
                    Text(
                      'Could not start the app:\n${appState.initError}',
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 16),
                    FilledButton(
                      onPressed: () => appState.init(),
                      child: const Text('Retry'),
                    ),
                  ],
                ),
              ),
            ),
          );
        }
        if (!appState.hasAcceptedUserAgreement) {
          return const UserAgreementScreen();
        }
        return const MainShell();
      },
    );
  }
}