import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import '../../../../core/services/auth_service.dart';

/// Página para o aluno entrar numa turma usando o código
class JoinClassPage extends StatefulWidget {
  const JoinClassPage({super.key});

  @override
  State<JoinClassPage> createState() => _JoinClassPageState();
}

class _JoinClassPageState extends State<JoinClassPage> {
  final _codeController = TextEditingController();
  bool _isLoading = false;

  @override
  void dispose() {
    _codeController.dispose();
    super.dispose();
  }

  Future<void> _joinClass() async {
    final code = _codeController.text.trim().toUpperCase();

    if (code.isEmpty) {
      _showError('Insere o código da turma');
      return;
    }

    setState(() => _isLoading = true);

    try {
      final currentUser = AuthService.currentUser;

      if (currentUser == null) {
        setState(() => _isLoading = false);
        _showError('Erro: Utilizador não autenticado');
        return;
      }

      // Verificar role — apenas alunos podem entrar por código
      final userRole = await AuthService.getUserRole(currentUser.uid);
      if (userRole != 'student') {
        setState(() => _isLoading = false);
        _showError('Apenas alunos podem entrar em turmas por código.');
        return;
      }

      // Ler classId autorizado do aluno (definido no registo)
      final authorizedClassId = await AuthService.getStudentClassId(
        currentUser.uid,
      );

      // Procurar turma pelo código
      final classQuery = await FirebaseFirestore.instance
          .collection('classes')
          .where('code', isEqualTo: code)
          .limit(1)
          .get();

      if (classQuery.docs.isEmpty) {
        setState(() => _isLoading = false);
        _showError('Código de turma inválido');
        return;
      }

      final classDoc = classQuery.docs.first;
      final classId = classDoc.id;

      // Verificar se o aluno está autorizado a entrar nesta turma
      if (authorizedClassId == null || authorizedClassId != classId) {
        setState(() => _isLoading = false);
        _showError(
          'Não tens permissão para entrar nesta turma.\n'
          'O teu professor ainda não te adicionou a esta disciplina.',
        );
        return;
      }

      // Verificar se já está inscrito nesta turma
      final existingEnrollment = await FirebaseFirestore.instance
          .collection('enrollments')
          .where('classId', isEqualTo: classId)
          .where('studentId', isEqualTo: currentUser.uid)
          .limit(1)
          .get();

      if (existingEnrollment.docs.isNotEmpty) {
        setState(() => _isLoading = false);
        _showError('Já estás inscrito nesta turma');
        return;
      }

      // Criar documento de inscrição
      await FirebaseFirestore.instance.collection('enrollments').add({
        'classId': classId,
        'studentId': currentUser.uid,
        'studentName':
            currentUser.displayName ??
            currentUser.email?.split('@')[0] ??
            'Aluno',
        'joinedAt': FieldValue.serverTimestamp(),
      });

      setState(() => _isLoading = false);

      // Mostrar sucesso
      if (mounted) {
        ScaffoldMessenger.of(context).showSnackBar(
          const SnackBar(
            content: Text('Entraste na turma com sucesso!'),
            backgroundColor: Color(0xFF10B981),
            duration: Duration(seconds: 2),
          ),
        );

        // Voltar para a home
        Navigator.of(context).pop();
      }
    } catch (e) {
      setState(() => _isLoading = false);
      _showError('Erro ao entrar na turma: $e');
    }
  }

  void _showError(String message) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(
        content: Text(message),
        backgroundColor: const Color(0xFFEF4444),
        duration: const Duration(seconds: 3),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: const Color(0xFFF8F9FA),
      appBar: AppBar(
        backgroundColor: const Color(0xFF82C9BD),
        elevation: 0,
        leading: IconButton(
          icon: const Icon(Icons.arrow_back, color: Colors.white),
          onPressed: () => Navigator.of(context).pop(),
        ),
        title: const Text(
          'Entrar numa Turma',
          style: TextStyle(
            color: Colors.white,
            fontSize: 18,
            fontWeight: FontWeight.bold,
          ),
        ),
      ),
      body: Padding(
        padding: const EdgeInsets.all(24.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            // Ícone e descrição
            Center(
              child: Container(
                width: 80,
                height: 80,
                decoration: BoxDecoration(
                  color: const Color(0xFF82C9BD).withOpacity(0.1),
                  borderRadius: BorderRadius.circular(20),
                ),
                child: const Icon(
                  Icons.group_add,
                  color: Color(0xFF82C9BD),
                  size: 40,
                ),
              ),
            ),
            const SizedBox(height: 24),
            const Center(
              child: Text(
                'Insere o código da turma',
                style: TextStyle(
                  color: Color(0xFF2D3748),
                  fontSize: 18,
                  fontWeight: FontWeight.bold,
                ),
              ),
            ),
            const SizedBox(height: 8),
            Center(
              child: Text(
                'O professor partilhou contigo um código de 6 caracteres.',
                style: TextStyle(color: Colors.grey[600], fontSize: 14),
                textAlign: TextAlign.center,
              ),
            ),
            const SizedBox(height: 32),

            // Campo de código
            Container(
              decoration: BoxDecoration(
                color: Colors.white,
                borderRadius: BorderRadius.circular(12),
                border: Border.all(color: const Color(0xFFE2E8F0), width: 1),
              ),
              child: TextField(
                controller: _codeController,
                textCapitalization: TextCapitalization.characters,
                maxLength: 6,
                style: const TextStyle(
                  fontSize: 20,
                  fontWeight: FontWeight.bold,
                  letterSpacing: 4,
                  color: Color(0xFF2D3748),
                ),
                textAlign: TextAlign.center,
                decoration: InputDecoration(
                  hintText: 'XXXXXX',
                  hintStyle: TextStyle(
                    fontSize: 20,
                    fontWeight: FontWeight.bold,
                    letterSpacing: 4,
                    color: Colors.grey[400],
                  ),
                  border: InputBorder.none,
                  contentPadding: const EdgeInsets.all(20),
                  counterText: '',
                ),
              ),
            ),
            const SizedBox(height: 24),

            // Botão de entrar
            SizedBox(
              width: double.infinity,
              height: 56,
              child: ElevatedButton(
                onPressed: _isLoading ? null : _joinClass,
                style: ElevatedButton.styleFrom(
                  backgroundColor: const Color(0xFF82C9BD),
                  foregroundColor: Colors.white,
                  elevation: 0,
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(12),
                  ),
                  disabledBackgroundColor: const Color(
                    0xFF82C9BD,
                  ).withOpacity(0.5),
                ),
                child: _isLoading
                    ? const SizedBox(
                        width: 24,
                        height: 24,
                        child: CircularProgressIndicator(
                          color: Colors.white,
                          strokeWidth: 2,
                        ),
                      )
                    : const Text(
                        'Entrar na Turma',
                        style: TextStyle(
                          fontSize: 16,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
              ),
            ),
          ],
        ),
      ),
    );
  }
}