#144

DataLayer/Repositories/IStudentSubjectRegistrationRepository.cs

@@ -12,4 +12,5 @@ public Task<List<StudentSubjectRegistration>> GetBySubjectAsync(
 
 	//public Task<List<StudentSubjectRegistration>> GetByStudentAndTimeAsync(int studentId, DayOfWeek day, ScheduleSlotInDay slot, CancellationToken cancellationToken = default);
 	Task<List<StudentSubjectRegistration>> GetRegistrationsByStudent(int studentId);
+	Task<int> CountMainRegistrationsForSubjectAsync(int subjectId);
 }

DataLayer/Repositories/StudentSubjectRegistrationDbRepository.cs

@@ -1,4 +1,5 @@
 using MensaGymnazium.IntranetGen3.Model;
+using MensaGymnazium.IntranetGen3.Primitives;
 
 namespace MensaGymnazium.IntranetGen3.DataLayer.Repositories;
 
@@ -13,4 +14,11 @@ public Task<List<StudentSubjectRegistration>> GetRegistrationsByStudent(int stud
 	{
 		return Data.Where(ssr => ssr.StudentId == studentId).ToListAsync();
 	}
+
+	public async Task<int> CountMainRegistrationsForSubjectAsync(int subjectId)
+	{
+		return await Data.CountAsync(
+			ssr => ssr.SubjectId == subjectId
+			&& ssr.RegistrationType == StudentRegistrationType.Main);
+	}
 }

Facades/SubjectRegistrationsManagerFacade.cs

@@ -63,6 +63,13 @@ public async Task CreateRegistrationAsync(StudentSubjectRegistrationCreateDto st
 								"Přihlášku není možné vytvořit. Je před, nebo již po termínu přihlašování");
 		}
 
+		// Verify subject isn't full
+		if (await subjectRegistrationsManagerService
+				.IsSubjectCapacityFullAsync(studentSubjectRegistrationCreateDto.SubjectId.Value))
+		{
+			throw new OperationFailedException("Předmět je již plný");
+		}
+
 		// Create registration
 		var currentUser = applicationAuthenticationService.GetCurrentUser();
 		Contract.Requires<SecurityException>(currentUser.StudentId is not null);

Services/SubjectRegistration/ISubjectRegistrationsManagerService.cs

@@ -33,4 +33,7 @@ public StudentSubjectRegistration CreateNewSubjectRegistration(
 	/// <param name="cancellationToken"></param>
 	/// <returns></returns>
 	public Task CancelRegistrationAsync(int registrationId, int callerStudentId, CancellationToken cancellationToken = default);
+
+	/// <returns>True, if the number of registrations for this subject reached the subject's capacity</returns>
+	Task<bool> IsSubjectCapacityFullAsync(int subjectId);
 }

Services/SubjectRegistration/SubjectRegistrationsManagerService.cs

@@ -14,17 +14,20 @@ internal sealed class SubjectRegistrationsManagerService : ISubjectRegistrations
 	private readonly IApplicationSettingsEntries applicationSettingsEntries;
 	private readonly IUnitOfWork unitOfWork;
 	private readonly IStudentSubjectRegistrationRepository studentSubjectRegistrationRepository;
+	private readonly ISubjectRepository subjectRepository;
 
 	public SubjectRegistrationsManagerService(
 		ITimeService timeService,
 		IApplicationSettingsEntries applicationSettingsEntries,
 		IUnitOfWork unitOfWork,
-		IStudentSubjectRegistrationRepository studentSubjectRegistrationRepository)
+		IStudentSubjectRegistrationRepository studentSubjectRegistrationRepository,
+		ISubjectRepository subjectRepository)
 	{
 		this.timeService = timeService;
 		this.applicationSettingsEntries = applicationSettingsEntries;
 		this.unitOfWork = unitOfWork;
 		this.studentSubjectRegistrationRepository = studentSubjectRegistrationRepository;
+		this.subjectRepository = subjectRepository;
 	}
 	public bool IsRegistrationPeriodActive()
 	{
@@ -70,4 +73,17 @@ public async Task CancelRegistrationAsync(int registrationId, int callerStudentI
 
 		unitOfWork.AddForDelete(studentSubjectRegistration);
 	}
+
+	public async Task<bool> IsSubjectCapacityFullAsync(int subjectId)
+	{
+		var subject = await subjectRepository.GetObjectAsync(subjectId);
+		if (subject.Capacity is null)
+		{
+			return false; // No capacity => no limit
+		}
+
+		var registrationsForSubject = await studentSubjectRegistrationRepository.CountMainRegistrationsForSubjectAsync(subjectId);
+
+		return registrationsForSubject >= subject.Capacity.Value;
+	}
 }