import 'dart:async';

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

import 'main.dart' show supabase;
import 'home_screen.dart';
import 'logged_home.dart';

final ValueNotifier<bool> forceHomeScreen = ValueNotifier<bool>(false);

class AuthGate extends StatefulWidget {
  const AuthGate({super.key});

  @override
  State<AuthGate> createState() => _AuthGateState();
}

class _AuthGateState extends State<AuthGate> {
  String? _validatedUserId;
  String? _validatingUserId;

  /// Confirma que a sessão ativa ainda corresponde a um perfil existente na
  /// base de dados. Sessões do Supabase Auth sobrevivem mesmo que os dados
  /// da conta tenham sido apagados (ex.: "Apagar dados da conta" ou remoção
  /// manual na base de dados) — sem esta verificação, essa conta "fantasma"
  /// continuaria a conseguir entrar.
  Future<void> _validateSession(String userId) async {
    if (_validatingUserId == userId) return;
    _validatingUserId = userId;
    try {
      final profile = await supabase
          .from('profiles')
          .select('id')
          .eq('id', userId)
          .maybeSingle();

      if (!mounted) return;

      if (profile == null) {
        unawaited(
          supabase
              .from('children')
              .delete()
              .eq('owner_id', userId)
              .catchError((_) => <Map<String, dynamic>>[]),
        );
        await supabase.auth.signOut();
      } else {
        setState(() => _validatedUserId = userId);
      }
    } catch (_) {
      // Falha de rede/consulta: não força logout, tenta novamente depois.
    } finally {
      _validatingUserId = null;
    }
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<bool>(
      valueListenable: forceHomeScreen,
      builder: (context, forcedHome, _) {
        return StreamBuilder<AuthState>(
          stream: supabase.auth.onAuthStateChange,
          initialData: AuthState(AuthChangeEvent.initialSession, supabase.auth.currentSession),
          builder: (context, snapshot) {
            final user = snapshot.data?.session?.user;

            if (user != null && user.id != _validatedUserId) {
              WidgetsBinding.instance.addPostFrameCallback((_) {
                if (mounted) _validateSession(user.id);
              });
            }

            final Widget child;
            if (snapshot.connectionState == ConnectionState.waiting) {
              child = const SizedBox.shrink();
            } else if (forcedHome || user == null || user.id != _validatedUserId) {
              child = const HomeScreen(key: ValueKey('home_screen'));
            } else {
              child = const LoggedHomeScreen(key: ValueKey('logged_home_screen'));
            }

            return AnimatedSwitcher(
              duration: const Duration(milliseconds: 280),
              reverseDuration: const Duration(milliseconds: 240),
              switchInCurve: Curves.easeOutCubic,
              switchOutCurve: Curves.easeInCubic,
              transitionBuilder: (child, animation) {
                final fade = CurvedAnimation(parent: animation, curve: Curves.easeOut);
                return FadeTransition(
                  opacity: fade,
                  child: ScaleTransition(
                    scale: Tween<double>(begin: 0.985, end: 1.0).animate(fade),
                    child: child,
                  ),
                );
              },
              child: child,
            );
          },
        );
      },
    );
  }
}