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

/// Página para visualizar os alunos de uma turma específica
class ClassStudentsPage extends StatefulWidget {
  final String classId;
  final String className;

  const ClassStudentsPage({
    super.key,
    required this.classId,
    required this.className,
  });

  @override
  State<ClassStudentsPage> createState() => _ClassStudentsPageState();
}

class _ClassStudentsPageState extends State<ClassStudentsPage> {
  bool _isCheckingAccess = true;
  bool _accessGranted = false;

  @override
  void initState() {
    super.initState();
    _verifyOwnership();
  }

  Future<void> _verifyOwnership() async {
    final currentUser = AuthService.currentUser;
    if (currentUser == null) {
      setState(() {
        _isCheckingAccess = false;
        _accessGranted = false;
      });
      return;
    }

    final role = await AuthService.getUserRole(currentUser.uid);
    if (role != 'teacher') {
      setState(() {
        _isCheckingAccess = false;
        _accessGranted = false;
      });
      return;
    }

    final classDoc = await FirebaseFirestore.instance
        .collection('classes')
        .doc(widget.classId)
        .get();

    final teacherId = classDoc.data()?['teacherId'] as String?;
    setState(() {
      _isCheckingAccess = false;
      _accessGranted = classDoc.exists && teacherId == currentUser.uid;
    });
  }

  @override
  Widget build(BuildContext context) {
    if (_isCheckingAccess) {
      return const Scaffold(
        backgroundColor: Color(0xFFF8F9FA),
        body: Center(
          child: CircularProgressIndicator(color: Color(0xFF82C9BD)),
        ),
      );
    }

    if (!_accessGranted) {
      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(
            'Acesso Negado',
            style: TextStyle(color: Colors.white, fontWeight: FontWeight.bold),
          ),
        ),
        body: Center(
          child: Padding(
            padding: const EdgeInsets.all(32.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                const Icon(
                  Icons.lock_outline,
                  size: 64,
                  color: Color(0xFF82C9BD),
                ),
                const SizedBox(height: 24),
                const Text(
                  'Sem permissão',
                  style: TextStyle(
                    color: Color(0xFF2D3748),
                    fontSize: 20,
                    fontWeight: FontWeight.bold,
                  ),
                ),
                const SizedBox(height: 12),
                Text(
                  'Só podes ver os alunos das tuas próprias turmas.',
                  style: TextStyle(color: Colors.grey[600], fontSize: 14),
                  textAlign: TextAlign.center,
                ),
              ],
            ),
          ),
        ),
      );
    }

    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: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              widget.className,
              style: const TextStyle(
                color: Colors.white,
                fontSize: 18,
                fontWeight: FontWeight.bold,
              ),
            ),
            const Text(
              'Alunos Matriculados',
              style: TextStyle(
                color: Colors.white70,
                fontSize: 13,
                fontWeight: FontWeight.w300,
              ),
            ),
          ],
        ),
      ),
      body: StreamBuilder<QuerySnapshot>(
        stream: FirebaseFirestore.instance
            .collection('enrollments')
            .where('classId', isEqualTo: widget.classId)
            .orderBy('joinedAt', descending: true)
            .snapshots(),
        builder: (context, snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return const Center(
              child: CircularProgressIndicator(color: Color(0xFF82C9BD)),
            );
          }

          if (snapshot.hasError) {
            return Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Icon(Icons.error_outline, size: 48, color: Colors.grey[400]),
                  const SizedBox(height: 16),
                  Text(
                    'Erro ao carregar alunos',
                    style: TextStyle(color: Colors.grey[600], fontSize: 16),
                  ),
                ],
              ),
            );
          }

          final enrollments = snapshot.data?.docs ?? [];

          if (enrollments.isEmpty) {
            return Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Icon(Icons.people_outline, size: 64, color: Colors.grey[300]),
                  const SizedBox(height: 24),
                  Text(
                    'Nenhum aluno entrou nesta turma ainda.',
                    style: TextStyle(color: Colors.grey[600], fontSize: 16),
                    textAlign: TextAlign.center,
                  ),
                  const SizedBox(height: 8),
                  Padding(
                    padding: const EdgeInsets.symmetric(horizontal: 32.0),
                    child: Text(
                      'Partilha o código da turma para os alunos se juntarem.',
                      style: TextStyle(color: Colors.grey[500], fontSize: 13),
                      textAlign: TextAlign.center,
                    ),
                  ),
                ],
              ),
            );
          }

          return ListView.builder(
            padding: const EdgeInsets.all(16.0),
            itemCount: enrollments.length,
            itemBuilder: (context, index) {
              final enrollment =
                  enrollments[index].data() as Map<String, dynamic>;
              final studentName =
                  enrollment['studentName'] as String? ?? 'Aluno sem nome';
              final joinedAt = enrollment['joinedAt'] as Timestamp?;

              return Container(
                margin: const EdgeInsets.only(bottom: 12.0),
                decoration: BoxDecoration(
                  color: Colors.white,
                  borderRadius: BorderRadius.circular(16.0),
                  boxShadow: [
                    BoxShadow(
                      color: Colors.black.withOpacity(0.05),
                      blurRadius: 10,
                      offset: const Offset(0, 4),
                    ),
                  ],
                ),
                child: ListTile(
                  contentPadding: const EdgeInsets.all(16.0),
                  leading: Container(
                    width: 48,
                    height: 48,
                    decoration: BoxDecoration(
                      color: const Color(0xFF82C9BD).withOpacity(0.1),
                      borderRadius: BorderRadius.circular(12.0),
                    ),
                    child: const Icon(
                      Icons.person,
                      color: Color(0xFF82C9BD),
                      size: 24,
                    ),
                  ),
                  title: Text(
                    studentName,
                    style: const TextStyle(
                      color: Color(0xFF2D3748),
                      fontSize: 16,
                      fontWeight: FontWeight.w600,
                    ),
                  ),
                  subtitle: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      const SizedBox(height: 4),
                      Text(
                        joinedAt != null
                            ? 'Entrou em ${_formatDate(joinedAt.toDate())}'
                            : 'Data desconhecida',
                        style: TextStyle(color: Colors.grey[600], fontSize: 13),
                      ),
                    ],
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }

  String _formatDate(DateTime date) {
    return DateFormat('dd/MM/yyyy').format(date);
  }
}