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) {
    final cs = Theme.of(context).colorScheme;

    if (_isCheckingAccess) {
      return Scaffold(
        backgroundColor: cs.surface,
        body: Center(child: CircularProgressIndicator(color: cs.primary)),
      );
    }

    if (!_accessGranted) {
      return Scaffold(
        backgroundColor: cs.surface,
        appBar: AppBar(
          backgroundColor: cs.surface,
          foregroundColor: cs.onSurface,
          elevation: 0,
          title: const Text('Acesso Negado'),
        ),
        body: Center(
          child: Padding(
            padding: const EdgeInsets.all(32.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Icon(Icons.lock_outline, size: 64, color: cs.primary),
                const SizedBox(height: 24),
                Text(
                  'Sem permissão',
                  style: TextStyle(
                    color: cs.onSurface,
                    fontSize: 20,
                    fontWeight: FontWeight.bold,
                  ),
                ),
                const SizedBox(height: 12),
                Text(
                  'Só podes ver os alunos das tuas próprias turmas.',
                  style: TextStyle(color: cs.onSurfaceVariant, fontSize: 14),
                  textAlign: TextAlign.center,
                ),
              ],
            ),
          ),
        ),
      );
    }

    return Scaffold(
      backgroundColor: cs.surface,
      appBar: AppBar(
        backgroundColor: cs.surface,
        foregroundColor: cs.onSurface,
        elevation: 0,
        title: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              widget.className,
              style: TextStyle(
                color: cs.onSurface,
                fontSize: 18,
                fontWeight: FontWeight.bold,
              ),
            ),
            Text(
              'Alunos Matriculados',
              style: TextStyle(
                color: cs.onSurfaceVariant,
                fontSize: 13,
                fontWeight: FontWeight.w400,
              ),
            ),
          ],
        ),
      ),
      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 Center(child: CircularProgressIndicator(color: cs.primary));
          }

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

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

          if (enrollments.isEmpty) {
            return Center(
              child: Padding(
                padding: const EdgeInsets.all(32),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: [
                    Icon(
                      Icons.people_outline,
                      size: 64,
                      color: cs.onSurfaceVariant.withValues(alpha: 0.4),
                    ),
                    const SizedBox(height: 24),
                    Text(
                      'Nenhum aluno entrou nesta turma ainda.',
                      style: TextStyle(
                        color: cs.onSurfaceVariant,
                        fontSize: 16,
                      ),
                      textAlign: TextAlign.center,
                    ),
                    const SizedBox(height: 8),
                    Text(
                      'Partilha o código da turma para os alunos se juntarem.',
                      style: TextStyle(
                        color: cs.onSurfaceVariant.withValues(alpha: 0.7),
                        fontSize: 13,
                      ),
                      textAlign: TextAlign.center,
                    ),
                  ],
                ),
              ),
            );
          }

          return ListView.separated(
            padding: const EdgeInsets.all(16),
            itemCount: enrollments.length,
            separatorBuilder: (_, __) => const SizedBox(height: 12),
            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?;
              final enrollmentId = enrollments[index].id;

              return Container(
                decoration: BoxDecoration(
                  color: cs.surface,
                  borderRadius: BorderRadius.circular(16),
                  border: Border.all(color: cs.outline.withValues(alpha: 0.15)),
                  boxShadow: [
                    BoxShadow(
                      color: cs.shadow.withValues(alpha: 0.05),
                      blurRadius: 8,
                      offset: const Offset(0, 2),
                    ),
                  ],
                ),
                child: ListTile(
                  contentPadding: const EdgeInsets.symmetric(
                    horizontal: 16,
                    vertical: 8,
                  ),
                  leading: Container(
                    width: 48,
                    height: 48,
                    decoration: BoxDecoration(
                      color: cs.primary.withValues(alpha: 0.1),
                      borderRadius: BorderRadius.circular(12),
                    ),
                    child: Icon(Icons.person, color: cs.primary, size: 24),
                  ),
                  title: Text(
                    studentName,
                    style: TextStyle(
                      color: cs.onSurface,
                      fontSize: 15,
                      fontWeight: FontWeight.w600,
                    ),
                  ),
                  subtitle: Padding(
                    padding: const EdgeInsets.only(top: 4),
                    child: Text(
                      joinedAt != null
                          ? 'Entrou em ${_formatDate(joinedAt.toDate())}'
                          : 'Data desconhecida',
                      style: TextStyle(
                        color: cs.onSurfaceVariant,
                        fontSize: 13,
                      ),
                    ),
                  ),
                  trailing: IconButton(
                    icon: Icon(Icons.delete_outline, color: cs.error),
                    onPressed: () => _showRemoveStudentDialog(
                      context,
                      enrollmentId,
                      studentName,
                    ),
                    tooltip: 'Remover aluno',
                  ),
                ),
              );
            },
          );
        },
      ),
    );
  }

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

  Future<void> _showRemoveStudentDialog(
    BuildContext context,
    String enrollmentId,
    String studentName,
  ) async {
    final confirmed = await showDialog<bool>(
      context: context,
      builder: (context) => AlertDialog(
        title: const Text('Remover Aluno'),
        content: Text(
          'Tem a certeza que deseja remover $studentName desta turma?',
        ),
        actions: [
          TextButton(
            onPressed: () => Navigator.of(context).pop(false),
            child: const Text('Cancelar'),
          ),
          TextButton(
            onPressed: () => Navigator.of(context).pop(true),
            style: TextButton.styleFrom(
              foregroundColor: Theme.of(context).colorScheme.error,
            ),
            child: const Text('Remover'),
          ),
        ],
      ),
    );

    if (confirmed == true && context.mounted) {
      try {
        await FirebaseFirestore.instance
            .collection('enrollments')
            .doc(enrollmentId)
            .delete();

        if (context.mounted) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(
              content: Row(
                children: [
                  Icon(Icons.check_circle, color: Colors.white),
                  const SizedBox(width: 12),
                  const Text('Aluno removido com sucesso'),
                ],
              ),
              backgroundColor: Colors.green,
              behavior: SnackBarBehavior.floating,
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(10),
              ),
              duration: const Duration(seconds: 3),
            ),
          );
        }
      } catch (e) {
        if (context.mounted) {
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(
              content: Row(
                children: [
                  Icon(Icons.error_outline, color: Colors.white),
                  const SizedBox(width: 12),
                  Text('Erro ao remover aluno: $e'),
                ],
              ),
              backgroundColor: Colors.red,
              behavior: SnackBarBehavior.floating,
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(10),
              ),
              duration: const Duration(seconds: 4),
            ),
          );
        }
      }
    }
  }
}