Improve variable and function names for clarity across service, repository, middleware, and frontend layers

api/CourseRegistration.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -56,16 +56,16 @@ private async Task HandleExceptionAsync(HttpContext context, Exception exception
 
         switch (exception)
         {
-            case ArgumentException argEx:
+            case ArgumentException argumentException:
                 response.StatusCode = (int)HttpStatusCode.BadRequest;
                 errorResponse.Message = "Invalid argument provided";
-                errorResponse.Errors = new[] { argEx.Message };
+                errorResponse.Errors = new[] { argumentException.Message };
                 break;
 
-            case InvalidOperationException invOpEx:
+            case InvalidOperationException invalidOperationException:
                 response.StatusCode = (int)HttpStatusCode.BadRequest;
                 errorResponse.Message = "Invalid operation";
-                errorResponse.Errors = new[] { invOpEx.Message };
+                errorResponse.Errors = new[] { invalidOperationException.Message };
                 break;
 
             case UnauthorizedAccessException:

api/CourseRegistration.Application/Services/CertificateService.cs

@@ -92,15 +92,15 @@ public async Task<IEnumerable<CertificateDto>> GetCertificatesByStudentIdAsync(G
         await Task.CompletedTask; // Simulate async operation
 
         var certificates = _certificates.Where(c => c.StudentId == studentId);
-        return certificates.Select(MapToDto);
+        return certificates.Select(MapCertificateToDto);
     }
 
     public async Task<CertificateDto?> GetCertificateByIdAsync(Guid certificateId)
     {
         await Task.CompletedTask; // Simulate async operation
 
         var certificate = _certificates.FirstOrDefault(c => c.CertificateId == certificateId);
-        return certificate != null ? MapToDto(certificate) : null;
+        return certificate != null ? MapCertificateToDto(certificate) : null;
     }
 
     public async Task<IEnumerable<CertificateDto>> GetCertificatesByStudentNameAsync(string studentName)
@@ -118,7 +118,7 @@ public async Task<IEnumerable<CertificateDto>> GetCertificatesByStudentNameAsync
             certificates.AddRange(_certificates.Where(c => c.StudentId == student.StudentId));
         }
 
-        return certificates.Select(MapToDto);
+        return certificates.Select(MapCertificateToDto);
     }
 
     public async Task<CertificateDto> CreateCertificateAsync(CreateCertificateDto createCertificateDto)
@@ -138,17 +138,17 @@ public async Task<CertificateDto> CreateCertificateAsync(CreateCertificateDto cr
         };
 
         _certificates.Add(certificate);
-        return MapToDto(certificate);
+        return MapCertificateToDto(certificate);
     }
 
     public string GenerateCertificateNumber()
     {
-        var year = DateTime.Now.Year;
-        var sequence = _certificates.Count + 1;
-        return $"CERT-{year}-{sequence:D3}";
+        var issuanceYear = DateTime.UtcNow.Year;
+        var certificateSequenceNumber = _certificates.Count + 1;
+        return $"CERT-{issuanceYear}-{certificateSequenceNumber:D3}";
     }
 
-    private CertificateDto MapToDto(Certificate certificate)
+    private CertificateDto MapCertificateToDto(Certificate certificate)
     {
         var student = _students.FirstOrDefault(s => s.StudentId == certificate.StudentId);
         var course = _courses.FirstOrDefault(c => c.CourseId == certificate.CourseId);

api/CourseRegistration.Infrastructure/Repositories/CourseRepository.cs

@@ -39,16 +39,16 @@ public async Task<IEnumerable<Course>> SearchCoursesAsync(string? searchTerm, st
 
         if (!string.IsNullOrWhiteSpace(searchTerm))
         {
-            var lowerSearchTerm = searchTerm.ToLower();
+            var normalizedSearchTerm = searchTerm.ToLower();
             query = query.Where(c => 
-                c.CourseName.ToLower().Contains(lowerSearchTerm) ||
-                (c.Description != null && c.Description.ToLower().Contains(lowerSearchTerm)));
+                c.CourseName.ToLower().Contains(normalizedSearchTerm) ||
+                (c.Description != null && c.Description.ToLower().Contains(normalizedSearchTerm)));
         }
 
         if (!string.IsNullOrWhiteSpace(instructor))
         {
-            var lowerInstructor = instructor.ToLower();
-            query = query.Where(c => c.InstructorName.ToLower().Contains(lowerInstructor));
+            var normalizedInstructorName = instructor.ToLower();
+            query = query.Where(c => c.InstructorName.ToLower().Contains(normalizedInstructorName));
         }
 
         return await query
@@ -72,11 +72,11 @@ public async Task<IEnumerable<Course>> GetActiveCoursesAsync()
     /// </summary>
     public async Task<IEnumerable<Course>> GetAvailableCoursesAsync()
     {
-        var currentDate = DateTime.UtcNow;
+        var currentUtcDateTime = DateTime.UtcNow;
 
         return await _dbSet
             .Include(c => c.Registrations)
-            .Where(c => c.IsActive && c.StartDate > currentDate)
+            .Where(c => c.IsActive && c.StartDate > currentUtcDateTime)
             .OrderBy(c => c.StartDate)
             .ThenBy(c => c.CourseName)
             .ToListAsync();
@@ -90,9 +90,9 @@ public async Task<IEnumerable<Course>> GetCoursesByInstructorAsync(string instru
         if (string.IsNullOrWhiteSpace(instructorName))
             return Enumerable.Empty<Course>();
 
-        var lowerInstructorName = instructorName.ToLower();
+        var normalizedInstructorName = instructorName.ToLower();
         return await _dbSet
-            .Where(c => c.IsActive && c.InstructorName.ToLower().Contains(lowerInstructorName))
+            .Where(c => c.IsActive && c.InstructorName.ToLower().Contains(normalizedInstructorName))
             .OrderBy(c => c.CourseName)
             .ToListAsync();
     }

frontend/script.js

@@ -61,12 +61,12 @@ function initializeForm() {
     addCourseForm.addEventListener('submit', handleFormSubmit);
 
     // Instructor name validation (letters, spaces, periods only)
-    document.getElementById('instructorName').addEventListener('input', function(e) {
-        const value = e.target.value;
+    document.getElementById('instructorName').addEventListener('input', function(event) {
+        const value = event.target.value;
         const validPattern = /^[a-zA-Z\s.]*$/;
 
         if (!validPattern.test(value)) {
-            e.target.value = value.replace(/[^a-zA-Z\s.]/g, '');
+            event.target.value = value.replace(/[^a-zA-Z\s.]/g, '');
         }
     });
 
@@ -80,8 +80,8 @@ function initializeForm() {
 }
 
 // Form Submission Handler
-async function handleFormSubmit(e) {
-    e.preventDefault();
+async function handleFormSubmit(event) {
+    event.preventDefault();
 
     if (!validateForm()) {
         return;
@@ -252,8 +252,8 @@ function clearAllErrors() {
     const errorElements = document.querySelectorAll('.error-message');
     const inputElements = document.querySelectorAll('.form-input, .form-textarea');
 
-    errorElements.forEach(el => el.textContent = '');
-    inputElements.forEach(el => el.classList.remove('error'));
+    errorElements.forEach(errorElement => errorElement.textContent = '');
+    inputElements.forEach(inputElement => inputElement.classList.remove('error'));
 }
 
 function displayValidationErrors(errors) {
@@ -284,19 +284,19 @@ function mapFieldName(apiFieldName) {
 }
 
 // UI State Functions
-function setSubmitButton(loading, text) {
-    submitBtn.disabled = loading;
-    submitText.textContent = text;
+function setSubmitButton(isLoading, buttonText) {
+    submitBtn.disabled = isLoading;
+    submitText.textContent = buttonText;
 
-    if (loading) {
-        submitBtn.innerHTML = `<i class="fas fa-spinner fa-spin"></i> ${text}`;
+    if (isLoading) {
+        submitBtn.innerHTML = `<i class="fas fa-spinner fa-spin"></i> ${buttonText}`;
     } else {
-        submitBtn.innerHTML = `<i class="fas fa-plus"></i> ${text}`;
+        submitBtn.innerHTML = `<i class="fas fa-plus"></i> ${buttonText}`;
     }
 }
 
-function showLoading(show) {
-    loadingOverlay.classList.toggle('hidden', !show);
+function showLoading(isVisible) {
+    loadingOverlay.classList.toggle('hidden', !isVisible);
 }
 
 // Modal Functions
@@ -863,8 +863,8 @@ function applyFilters() {
     let filteredRegistrations = allRegistrations;
 
     if (statusFilter !== '') {
-        filteredRegistrations = filteredRegistrations.filter(reg => 
-            reg.status.toString() === statusFilter
+        filteredRegistrations = filteredRegistrations.filter(registration => 
+            registration.status.toString() === statusFilter
         );
     }