saqel/apps/student_app/lib/logic/cubits/exam_cubit.dart

/// ==============================================================================
/// SAQEL ENTERPRISE (EDTECH 2.0) - ADAPTIVE EXAM STATE MANAGEMENT (CUBIT)
/// ==============================================================================
/// 
/// ملف: exam_cubit.dart
/// الهدف المعماري:
/// إدارة حالة دورة حياة الامتحانات التكيفية والتشخيص الذكي في تطبيق الطالب:
/// 1. جلب الامتحانات مباشرة من واجهات السيرفر (Pure API-Driven) دون أي بيانات أو أسئلة محلية ثابتة.
/// 2. إدارة المؤقت التنازلي الذكي ومزامنة الوقت المتبقي.
/// 3. إدارة التنقل بين الأسئلة وحفظ اختيارات الطالب وتحديد البدائل المحددة.
/// 4. إرسال الإجابات إلى السيرفر لتصحيحها واستلام تقرير التشخيص السقراطي ومؤشر الجاهزية للتوجيهي.
library;

import 'dart:async';
import 'package:flutter_bloc/flutter_bloc.dart';
import '../../data/models/exam_model.dart';
import '../../data/repositories/app_repositories.dart';

/// الحالات العامة للامتحان
abstract class ExamState {}

/// الحالة المبدئية قبل بدء التحميل
class ExamInitial extends ExamState {}

/// حالة انتظار جلب الأسئلة من السيرفر
class ExamLoading extends ExamState {
  final String message;
  ExamLoading({this.message = 'جاري تحضير الامتحان والأسئلة التكيفية من السيرفر...'});
}

class ExamLoaded extends ExamState {
  final ExamModel exam;
  final int currentQuestionIndex;
  final Map<int, int> selectedAnswers; // questionId -> optionId
  final int remainingSeconds;
  final bool isSubmitting;

  ExamLoaded({
    required this.exam,
    this.currentQuestionIndex = 0,
    this.selectedAnswers = const {},
    required this.remainingSeconds,
    this.isSubmitting = false,
  });

  QuestionModel? get currentQuestion {
    if (exam.questions.isEmpty || currentQuestionIndex >= exam.questions.length) return null;
    return exam.questions[currentQuestionIndex];
  }

  bool get isLastQuestion => currentQuestionIndex == exam.questions.length - 1;
  int get answeredCount => selectedAnswers.length;

  ExamLoaded copyWith({
    ExamModel? exam,
    int? currentQuestionIndex,
    Map<int, int>? selectedAnswers,
    int? remainingSeconds,
    bool? isSubmitting,
  }) {
    return ExamLoaded(
      exam: exam ?? this.exam,
      currentQuestionIndex: currentQuestionIndex ?? this.currentQuestionIndex,
      selectedAnswers: selectedAnswers ?? this.selectedAnswers,
      remainingSeconds: remainingSeconds ?? this.remainingSeconds,
      isSubmitting: isSubmitting ?? this.isSubmitting,
    );
  }
}

class ExamCompleted extends ExamState {
  final ExamModel exam;
  final ExamSubmissionResultModel result;
  final int timeSpentSeconds;

  ExamCompleted({
    required this.exam,
    required this.result,
    required this.timeSpentSeconds,
  });
}

class ExamError extends ExamState {
  final String message;
  ExamError(this.message);
}

class ExamCubit extends Cubit<ExamState> {
  final ExamRepository _repository;
  Timer? _countdownTimer;
  int _initialSeconds = 0;

  ExamCubit({ExamRepository? repository})
      : _repository = repository ?? ExamRepository(),
        super(ExamInitial());

  @override
  Future<void> close() {
    _countdownTimer?.cancel();
    return super.close();
  }

  Future<void> loadExam({int examId = 1, ExamModel? initialExam}) async {
    emit(ExamLoading());
    try {
      ExamModel loadedExam;
      if (initialExam != null && initialExam.questions.isNotEmpty) {
        loadedExam = initialExam;
      } else {
        loadedExam = await _repository.getExamDetails(examId);
      }

      if (loadedExam.questions.isEmpty) {
        emit(ExamError('لم يتم العثور على أسئلة لهذا الامتحان في السيرفر. يرجى توليد بنك الأسئلة من لوحة المناهج.'));
        return;
      }

      _initialSeconds = loadedExam.durationMinutes * 60;
      emit(ExamLoaded(
        exam: loadedExam,
        remainingSeconds: _initialSeconds,
      ));

      _startTimer();
    } catch (e) {
      emit(ExamError('تعذر جلب الامتحان من السيرفر: ${e.toString()}'));
    }
  }

  void _startTimer() {
    _countdownTimer?.cancel();
    _countdownTimer = Timer.periodic(const Duration(seconds: 1), (timer) {
      final s = state;
      if (s is ExamLoaded) {
        if (s.remainingSeconds <= 1) {
          timer.cancel();
          submitCurrentExam();
        } else {
          emit(s.copyWith(remainingSeconds: s.remainingSeconds - 1));
        }
      } else {
        timer.cancel();
      }
    });
  }

  void selectOption(int questionId, int optionId) {
    final s = state;
    if (s is ExamLoaded) {
      final updatedAnswers = Map<int, int>.from(s.selectedAnswers);
      updatedAnswers[questionId] = optionId;
      emit(s.copyWith(selectedAnswers: updatedAnswers));
    }
  }

  void goToQuestion(int index) {
    final s = state;
    if (s is ExamLoaded) {
      if (index >= 0 && index < s.exam.questions.length) {
        emit(s.copyWith(currentQuestionIndex: index));
      }
    }
  }

  void nextQuestion() {
    final s = state;
    if (s is ExamLoaded && !s.isLastQuestion) {
      emit(s.copyWith(currentQuestionIndex: s.currentQuestionIndex + 1));
    }
  }

  void previousQuestion() {
    final s = state;
    if (s is ExamLoaded && s.currentQuestionIndex > 0) {
      emit(s.copyWith(currentQuestionIndex: s.currentQuestionIndex - 1));
    }
  }

  Future<void> submitCurrentExam() async {
    final s = state;
    if (s is! ExamLoaded) return;

    _countdownTimer?.cancel();
    emit(s.copyWith(isSubmitting: true));

    final timeSpent = _initialSeconds - s.remainingSeconds;
    final formattedAnswers = s.selectedAnswers.entries.map((e) {
      return {
        'question_id': e.key,
        'selected_option_id': e.value,
      };
    }).toList();

    try {
      final result = await _repository.submitExam(
        s.exam.id,
        answers: formattedAnswers,
        timeSpentSeconds: timeSpent,
      );

      emit(ExamCompleted(
        exam: s.exam,
        result: result,
        timeSpentSeconds: timeSpent,
      ));
    } catch (e) {
      emit(ExamError('فشل تقديم الامتحان: ${e.toString()}'));
    }
  }

}