import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_test/flutter_test.dart';
import 'package:provider/provider.dart';
import 'package:shared_preferences/shared_preferences.dart';

import 'package:fuel_tax_tracker/main.dart';
import 'package:fuel_tax_tracker/screens/main_shell.dart';
import 'package:fuel_tax_tracker/screens/user_agreement_screen.dart';
import 'package:fuel_tax_tracker/services/app_state.dart';

/// Covers [UserAgreementScreen] — the liability gate `main.dart`'s
/// `AppRoot` shows before [MainShell] until [AppState.hasAcceptedUserAgreement]
/// is true, so a fresh install sees it before anything else, including the
/// onboarding tour.
void main() {
  setUp(() {
    SharedPreferences.setMockInitialValues({});
  });

  Future<AppState> pumpScreen(WidgetTester tester) async {
    // AppState.hasAcceptedUserAgreement defaults to true precisely so that
    // ad-hoc AppState() construction in every other screen's tests doesn't
    // trigger this gate — these tests explicitly flip it to false to
    // reproduce a real fresh install's state.
    final appState = AppState()
      ..isLoading = false
      ..hasAcceptedUserAgreement = false;
    await tester.pumpWidget(
      ChangeNotifierProvider.value(
        value: appState,
        child: const MaterialApp(home: UserAgreementScreen()),
      ),
    );
    return appState;
  }

  testWidgets('shows the data-loss liability section and both actions', (tester) async {
    await pumpScreen(tester);

    expect(find.text('We Are Not Responsible for Your Data or Any Data Loss'), findsOneWidget);
    expect(find.textContaining('developer is not responsible for your data'), findsOneWidget);
    expect(find.widgetWithText(FilledButton, 'I Agree'), findsOneWidget);
    expect(find.widgetWithText(OutlinedButton, 'Decline'), findsOneWidget);
  });

  testWidgets('I Agree marks the agreement accepted and persists it', (tester) async {
    final appState = await pumpScreen(tester);

    await tester.tap(find.widgetWithText(FilledButton, 'I Agree'));
    await tester.pumpAndSettle();

    expect(appState.hasAcceptedUserAgreement, isTrue);

    final prefs = await SharedPreferences.getInstance();
    expect(prefs.getBool('has_accepted_user_agreement'), isTrue,
        reason: 'persisted so the agreement never shows again on this device');
  });

  testWidgets('Decline asks the platform to close the app, without accepting', (tester) async {
    final appState = await pumpScreen(tester);

    final calls = <MethodCall>[];
    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
        .setMockMethodCallHandler(SystemChannels.platform, (call) async {
      calls.add(call);
      return null;
    });
    addTearDown(() {
      TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
          .setMockMethodCallHandler(SystemChannels.platform, null);
    });

    await tester.tap(find.widgetWithText(OutlinedButton, 'Decline'));
    await tester.pumpAndSettle();

    expect(calls.map((c) => c.method), contains('SystemNavigator.pop'));
    expect(appState.hasAcceptedUserAgreement, isFalse);
  });

  group('AppRoot gating', () {
    Future<AppState> pumpRoot(WidgetTester tester, {required bool hasAcceptedUserAgreement}) async {
      final appState = AppState()
        ..isLoading = false
        ..hasAcceptedUserAgreement = hasAcceptedUserAgreement;
      await tester.pumpWidget(
        ChangeNotifierProvider.value(
          value: appState,
          child: const MaterialApp(home: AppRoot()),
        ),
      );
      return appState;
    }

    testWidgets('shows UserAgreementScreen instead of MainShell before it is accepted',
        (tester) async {
      await pumpRoot(tester, hasAcceptedUserAgreement: false);

      expect(find.byType(UserAgreementScreen), findsOneWidget);
      expect(find.byType(MainShell), findsNothing);
    });

    testWidgets('shows MainShell once the agreement is accepted', (tester) async {
      final appState = await pumpRoot(tester, hasAcceptedUserAgreement: false);

      await tester.tap(find.widgetWithText(FilledButton, 'I Agree'));
      await tester.pumpAndSettle();

      expect(appState.hasAcceptedUserAgreement, isTrue);
      expect(find.byType(UserAgreementScreen), findsNothing);
      expect(find.byType(MainShell), findsOneWidget);
    });

    testWidgets('shows MainShell directly when already accepted (returning user)', (tester) async {
      await pumpRoot(tester, hasAcceptedUserAgreement: true);

      expect(find.byType(UserAgreementScreen), findsNothing);
      expect(find.byType(MainShell), findsOneWidget);
    });
  });
}