Membangun Ulang Laravel E-Learning ke Java Spring Boot & React: Arsitektur Enterprise & Migrasi Cloud-Ready

@Configuration
@EnableWebSecurity
@EnableMethodSecurity
@RequiredArgsConstructor
public class SecurityConfig {

    private final JwtAuthenticationFilter jwtAuthenticationFilter;
    private final CustomUserDetailsService userDetailsService;

    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http
            .cors(cors -> cors.configurationSource(corsConfigurationSource()))
            .csrf(AbstractHttpConfigurer::disable)
            .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
            .authorizeHttpRequests(auth -> auth
                .requestMatchers(
                    "/api/v1/auth/**",
                    "/swagger-ui/**",
                    "/v3/api-docs/**",
                    "/ws/**"
                ).permitAll()
                .requestMatchers("/api/v1/admin/**").hasRole("ADMIN")
                .requestMatchers("/api/v1/teacher/**").hasAnyRole("ADMIN", "TEACHER")
                .requestMatchers("/api/v1/student/**").hasAnyRole("ADMIN", "STUDENT")
                .anyRequest().authenticated()
            )
            .authenticationProvider(authenticationProvider())
            .addFilterBefore(jwtAuthenticationFilter, UsernamePasswordAuthenticationFilter.class);

        return http.build();
    }
}

@PostMapping("/impersonate")
@PreAuthorize("hasRole('ADMIN')")
public ResponseEntity<ApiResponse<AuthResponse>> impersonateUser(
        @Valid @RequestBody ImpersonateRequest request,
        @AuthenticationPrincipal UserPrincipal adminPrincipal) {
    
    User targetUser = userRepository.findByEmail(request.getEmail())
            .orElseThrow(() -> new ResourceNotFoundException("User tidak ditemukan"));
    
    // Hasilkan token berlingkup peran target yang tetap mencatat identitas admin sebagai audit
    String impersonationToken = jwtTokenProvider.generateTokenWithImpersonator(
            targetUser, 
            adminPrincipal.getEmail()
    );
    
    return ResponseEntity.ok(ApiResponse.success(
            "Impersonasi berhasil diaktifkan",
            new AuthResponse(impersonationToken, targetUser.getRole().name())
    ));
}

private long calculateRemainingSeconds(Examination exam, ExamAttempt attempt, LocalDateTime now) {
    LocalDateTime examDeadline = attempt.getStartedAt().plusMinutes(exam.getDurationMinutes());
    
    // Batas mutlak: durasi peserta tidak boleh melewati jadwal penutupan ujian serentak
    if (exam.getEndAt() != null && exam.getEndAt().isBefore(examDeadline)) {
        examDeadline = exam.getEndAt();
    }
    
    return Math.max(0, Duration.between(now, examDeadline).getSeconds());
}

// React 19: Deteksi perpindahan tab & minimalkan jendela ujian
useEffect(() => {
  const handleVisibilityChange = () => {
    if (document.hidden && attemptIdRef.current && !submittedResult) {
      api.post(`/exams/attempts/${attemptIdRef.current}/violation`, {
        reason: 'TAB_SWITCH_OR_MINIMIZED',
      }).then((res) => {
        const count = res.data.data.violations;
        setViolations(count);
        if (count >= 5) {
          alert('Batas pelanggaran keamanan tercapai (5x). Ujian otomatis dikumpulkan.');
          handleSubmitExam();
        }
      });
    }
  };

  document.addEventListener('visibilitychange', handleVisibilityChange);
  return () => document.removeEventListener('visibilitychange', handleVisibilityChange);
}, [submittedResult]);

realtimeService.broadcastExamEvent(exam.getId(), "STUDENT_VIOLATION", Map.of(
        "attemptId", attempt.getId(),
        "studentId", student.getId(),
        "studentName", student.getUser().getName(),
        "violations", attempt.getViolations(),
        "timestamp", LocalDateTime.now()
));

@Transactional
public BatchImportResult importStudentsFromExcel(MultipartFile file, Long classroomId) throws IOException {
    Classroom classroom = classroomRepository.findById(classroomId)
            .orElseThrow(() -> new ResourceNotFoundException("Kelas tidak ditemukan"));
            
    int successCount = 0;
    List<String> errors = new ArrayList<>();

    try (Workbook workbook = new XSSFWorkbook(file.getInputStream())) {
        Sheet sheet = workbook.getSheetAt(0);
        
        for (int i = 1; i <= sheet.getLastRowNum(); i++) {
            Row row = sheet.getRow(i);
            if (row == null) continue;
            
            try {
                String name = getCellValue(row.getCell(0));
                String email = getCellValue(row.getCell(1));
                String nis = getCellValue(row.getCell(2));
                
                provisionStudentAccount(name, email, nis, classroom);
                successCount++;
            } catch (Exception e) {
                errors.add("Baris " + (i + 1) + ": " + e.getMessage());
            }
        }
    }
    
    return new BatchImportResult(successCount, errors);
}

CREATE TABLE examinations (
    id BIGSERIAL PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    description TEXT,
    subject_id BIGINT NOT NULL REFERENCES subjects(id) ON DELETE CASCADE,
    teacher_id BIGINT NOT NULL REFERENCES teachers(id) ON DELETE CASCADE,
    classroom_id BIGINT NOT NULL REFERENCES classrooms(id) ON DELETE CASCADE,
    duration_minutes INT NOT NULL DEFAULT 60,
    passing_score INT NOT NULL DEFAULT 75,
    randomize_questions BOOLEAN DEFAULT FALSE,
    randomize_options BOOLEAN DEFAULT FALSE,
    allow_review BOOLEAN DEFAULT TRUE,
    start_at TIMESTAMP NOT NULL,
    end_at TIMESTAMP NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE exam_attempts (
    id BIGSERIAL PRIMARY KEY,
    examination_id BIGINT NOT NULL REFERENCES examinations(id) ON DELETE CASCADE,
    student_id BIGINT NOT NULL REFERENCES students(id) ON DELETE CASCADE,
    attempt_number INT NOT NULL DEFAULT 1,
    status VARCHAR(30) NOT NULL DEFAULT 'in_progress',
    score INT,
    passed BOOLEAN,
    violations INT DEFAULT 0,
    started_at TIMESTAMP NOT NULL,
    finished_at TIMESTAMP,
    CONSTRAINT uk_exam_student_attempt UNIQUE (examination_id, student_id, attempt_number)
);