Add Semesters (#42)

* Add `Semester` and `StudentSemester` entities

* Configure a many-to-many relationship between students and semesters

* Fix naming for DB tables and columns

* Add a name to `Semester` entity

* Fix outdated comment

* Add DTOs for semesters

* Replace `StudentGroupCreateDto` with `AssignStudentDto`

This change, in fact, only renames a record so it can be used in other services that require assigninging students to something.

* Add validation tests for the semester DTO

* Implement semester validation

* Implement `AssigningService` and `StudentGroupsService`

* Replace typeparams for `IStudentGroupsService`

* Add tests for assigning endpoints

* Remove `StudentGroup` logic from `GroupsService`

* Implement `SemestersService`

* Implement `StudentSemestersService`

* Add integration tests for semesters endpoints

* Implement endpoints for semesters

* Fix enrollments display

* Configure test data generation for semesters

* Fix a test

Core/Dtos/University/StudentGroupCreateDto.cs → Core/Dtos/University/AssignStudentDto.cs

@@ -3,4 +3,4 @@
 namespace EUniversity.Core.Dtos.University;
 
 [ValidateNever] // Remove data annotations validation
-public record StudentGroupCreateDto(string StudentId);
+public record AssignStudentDto(string StudentId);

Core/Dtos/University/SemesterCreateDto.cs

@@ -0,0 +1,6 @@
+using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
+
+namespace EUniversity.Core.Dtos.University;
+
+[ValidateNever] // Remove data annotations validation
+public record SemesterCreateDto(string Name, DateTimeOffset DateFrom, DateTimeOffset DateTo);

Core/Dtos/University/SemesterPreviewDto.cs

@@ -0,0 +1,3 @@
+namespace EUniversity.Core.Dtos.University;
+
+public record SemesterPreviewDto(int Id, string Name, DateTimeOffset DateFrom, DateTimeOffset DateTo);

Core/Dtos/University/SemesterViewDto.cs

@@ -0,0 +1,5 @@
+namespace EUniversity.Core.Dtos.University;
+
+public record SemesterViewDto(int Id, string Name,
+    DateTimeOffset DateFrom, DateTimeOffset DateTo,
+    IEnumerable<StudentSemesterViewDto> StudentEnrollments);

Core/Dtos/University/StudentSemesterViewDto.cs

@@ -0,0 +1,5 @@
+using EUniversity.Core.Dtos.Users;
+
+namespace EUniversity.Core.Dtos.University;
+
+public record StudentSemesterViewDto(StudentPreviewDto Student, DateTimeOffset EnrollmentDate);

Core/Models/University/Semester.cs

@@ -0,0 +1,34 @@
+namespace EUniversity.Core.Models.University;
+
+/// <summary>
+/// An entity that represents a semester.
+/// </summary>
+public class Semester : IEntity<int>, IHasName
+{
+    public const int MaxNameLength = 100;
+
+    [Key]
+    public int Id { get; set; }
+    /// <summary>
+    /// Name of the semester.
+    /// </summary>
+    [StringLength(MaxNameLength)]
+    public string Name { get; set; } = null!;
+    /// <summary>
+    /// Date when the semester starts.
+    /// </summary>
+    public DateTimeOffset DateFrom { get; set; }
+    /// <summary>
+    /// Date when the semester ends.
+    /// </summary>
+    public DateTimeOffset DateTo { get; set; }
+
+    /// <summary>
+    /// Navigation property to the students which are part of this semester.
+    /// </summary>
+    public ICollection<ApplicationUser> Students { get; set; } = null!;
+    /// <summary>
+    /// Navigation property to the student enrollments of this semester.
+    /// </summary>
+    public ICollection<StudentSemester> StudentEnrollments { get; set; } = null!;
+}

Core/Models/University/StudentSemester.cs

@@ -0,0 +1,38 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace EUniversity.Core.Models.University;
+
+/// <summary>
+/// Represents the entity used for configuring many-to-many relationship
+/// between students and semesters.
+/// </summary>
+public class StudentSemester : IEntity<int>
+{
+    [Key]
+    public int Id { get; set; }
+
+    /// <summary>
+    /// Date when student was added to the semester.
+    /// </summary>
+    public DateTimeOffset EnrollmentDate { get; set; }
+
+    /// <summary>
+    /// Foreign key of the associated student.
+    /// </summary>
+    [ForeignKey(nameof(Student))]
+    public string StudentId { get; set; } = null!;
+    /// <summary>
+    /// Foreign key of the associated semester.
+    /// </summary>
+    [ForeignKey(nameof(Semester))]
+    public int SemesterId { get; set; }
+
+    /// <summary>
+    /// Navigation property for the student associated with this semester.
+    /// </summary>
+    public ApplicationUser Student { get; set; } = null!;
+    /// <summary>
+    /// Navigation property for the semester that the student is part of.
+    /// </summary>
+    public Semester Semester { get; set; } = null!;
+}

Core/Services/IAssigningService.cs

@@ -0,0 +1,53 @@
+using System.Linq.Expressions;
+
+namespace EUniversity.Core.Services;
+
+/// <summary>
+/// Represents an interface for assigning/unassigning entities in a many-to-many relationship.
+/// </summary>
+/// <typeparam name="TAssigningEntity">A type of entity that configures a many-to-many relationship.</typeparam>
+/// <typeparam name="TId1">A type of the ID of the first entity.</typeparam>
+/// <typeparam name="TId2">A type of the ID of the second entity.</typeparam>
+public interface IAssigningService<TAssigningEntity, TId1, TId2>
+    where TAssigningEntity : class
+    where TId1 : IEquatable<TId1>
+    where TId2 : IEquatable<TId2>
+{
+    /// <summary>
+    /// Gets a predicate that can be used for finding
+    /// an instance of assigning entity in the database.
+    /// </summary>
+    /// <param name="id1">ID of the first entity.</param>
+    /// <param name="id2">ID of the second entity.</param>
+    /// <returns>
+    /// A predicate that can be used for finding
+    /// an instance of assigning entity in the database.
+    /// </returns>
+    public Expression<Func<TAssigningEntity, bool>> AssigningEntityPredicate(TId1 id1, TId2 id2);
+
+    /// <summary>
+    /// Adds the first entity to the second based on their IDs.
+    /// </summary>
+    /// <param name="entity1Id">ID of the first entity.</param>
+    /// <param name="entity2Id">ID of the second entity.</param>
+    /// <returns>
+    /// A task that represents the asynchronous operation. If the first entity was
+    /// successfully assigned to the second, it returns <see langword="true" />.
+    /// If the first entity was already assigned to the second, then <see langword="false" />
+    /// is returned.
+    /// </returns>
+    public Task<bool> AssignAsync(TId1 entity1Id, TId2 entity2Id);
+
+    /// <summary>
+    /// Unasigns the first entity from the second based on their IDs.
+    /// </summary>
+    /// <param name="entity1Id">ID of the first entity.</param>
+    /// <param name="entity2Id">ID of the second entity.</param>
+    /// <returns>
+    /// A task that represents the asynchronous operation. If the first entity was
+    /// successfully unassigned from the second, it returns <see langword="true" />.
+    /// If the first entity was not assigned to the second, then <see langword="false" />
+    /// is returned.
+    /// </returns>
+    public Task<bool> UnassignAsync(TId1 entity1Id, TId2 entity2Id);
+}

Core/Services/University/IGroupsService.cs

@@ -6,30 +6,4 @@ namespace EUniversity.Core.Services.University;
 public interface IGroupsService :
     ICrudService<Group, int, GroupPreviewDto, GroupViewDto, GroupCreateDto, GroupCreateDto>
 {
-    /// <summary>
-    /// Adds a student to a group based on the information.
-    /// </summary>
-    /// <param name="studentId">ID of the student to add to the group.</param>
-    /// <param name="groupId">ID of the group to which the user will be added.</param>
-    /// <returns>
-    /// A task that represents the asynchronous operation. If the student was
-    /// successfully added to the group, it returns <see langword="true" />.
-    /// If the student was already part of the group., then <see langword="false" />
-    /// is returned.
-    /// </returns>
-    Task<bool> AddStudentAsync(string studentId, int groupId);
-
-    /// <summary>
-    /// Removes a student from a group based on the information provided in the
-    /// <see cref="StudentGroupCreateDto" /> asynchronously.
-    /// </summary>
-    /// <param name="studentId">ID of the student to remove from the group.</param>
-    /// <param name="groupId">ID of the group from which the user will be removed.</param>
-    /// <returns>
-    /// A task that represents the asynchronous operation. If the student was
-    /// successfully removed from the group, it returns <see langword="true" />.
-    /// If the student was not part of the group., then <see langword="false" />
-    /// is returned.
-    /// </returns>
-    Task<bool> RemoveStudentAsync(string studentId, int groupId);
 }

Core/Services/University/ISemestersService.cs

@@ -0,0 +1,10 @@
+using EUniversity.Core.Dtos.University;
+using EUniversity.Core.Models.University;
+
+namespace EUniversity.Core.Services.University;
+
+public interface ISemestersService :
+    ICrudService<Semester, int, SemesterPreviewDto, SemesterViewDto, SemesterCreateDto, SemesterCreateDto>
+{
+
+}

Core/Services/University/IStudentGroupsService.cs

@@ -0,0 +1,11 @@
+using EUniversity.Core.Models.University;
+
+namespace EUniversity.Core.Services.University;
+
+/// <summary>
+/// Represents an interface of the service which configures
+/// the 'Students->Groups' many-to-many relationship.
+/// </summary>
+public interface IStudentGroupsService : IAssigningService<StudentGroup, int, string>
+{
+}

Core/Services/University/IStudentSemestersService.cs

@@ -0,0 +1,7 @@
+using EUniversity.Core.Models.University;
+
+namespace EUniversity.Core.Services.University;
+
+public interface IStudentSemestersService : IAssigningService<StudentSemester, int, string>
+{
+}

Core/Validation/University/StudentGroupCreateDtoValidator.cs → Core/Validation/University/AssignStudentDtoValidator.cs

@@ -7,9 +7,9 @@
 
 namespace EUniversity.Core.Validation.University;
 
-public class StudentGroupCreateDtoValidator : AbstractValidator<StudentGroupCreateDto>
+public class AssignStudentDtoValidator : AbstractValidator<AssignStudentDto>
 {
-    public StudentGroupCreateDtoValidator(UserManager<ApplicationUser> userManager)
+    public AssignStudentDtoValidator(UserManager<ApplicationUser> userManager)
     {
         RuleFor(sg => sg.StudentId)
             .NotEmpty()

Core/Validation/University/SemesterCreateDtoValidator.cs

@@ -0,0 +1,29 @@
+using EUniversity.Core.Dtos.University;
+using EUniversity.Core.Models.University;
+using FluentValidation;
+
+namespace EUniversity.Core.Validation.University;
+
+public class SemesterCreateDtoValidator : AbstractValidator<SemesterCreateDto>
+{
+    public SemesterCreateDtoValidator()
+    {
+        RuleFor(s => s.Name)
+            .NotEmpty()
+            .WithErrorCode(ValidationErrorCodes.PropertyRequired)
+            .WithMessage("Semester name is required");
+        RuleFor(s => s.Name)
+            .MaximumLength(Semester.MaxNameLength)
+            .WithErrorCode(ValidationErrorCodes.PropertyTooLarge)
+            .WithMessage($"Semester name cannot exceed {Semester.MaxNameLength} characters");
+
+        RuleFor(s => s.DateFrom)
+            .LessThan(s => s.DateTo)
+            .WithErrorCode(ValidationErrorCodes.InvalidRange)
+            .WithMessage("The from date must be earlier than the to date");
+        RuleFor(s => s.DateTo)
+            .GreaterThan(DateTimeOffset.Now)
+            .WithErrorCode(ValidationErrorCodes.InvalidRange)
+            .WithMessage("The to date must be in the future");
+    }
+}

Core/Validation/ValidationErrorCodes.cs

@@ -8,6 +8,7 @@ public static class ValidationErrorCodes
     public const string PropertyTooLarge = "PropertyTooLargeError";
     public const string InvalidProperty = "InvalidPropertyError";
     public const string InvalidEmail = "InvalidEmailError";
+    public const string InvalidRange = "InvalidRangeError";
     public const string Equal = "EqualError";
     public const string EmptyCollection = "EmptyCollectionError";
 

EUniversity.Tests/Validation/University/StudentGroupCreateDtoValidatorTests.cs → EUniversity.Tests/Validation/University/AssignStudentDtoValidatorTests.cs

@@ -5,9 +5,9 @@
 
 namespace EUniversity.Tests.Validation.University;
 
-public class StudentGroupCreateDtoValidatorTests : UsersValidatorTests
+public class AssignStudentDtoValidatorTests : UsersValidatorTests
 {
-    private StudentGroupCreateDtoValidator _validator;
+    private AssignStudentDtoValidator _validator;
 
     [OneTimeSetUp]
     public void OneTimeSetUp()
@@ -19,7 +19,7 @@ public void OneTimeSetUp()
     public async Task Dto_Valid_Succeeds()
     {
         // Arrange
-        StudentGroupCreateDto dto = new(TestStudentId);
+        AssignStudentDto dto = new(TestStudentId);
 
         // Act
         var result = await _validator.TestValidateAsync(dto);
@@ -35,7 +35,7 @@ public async Task Dto_Valid_Succeeds()
     public async Task StudentId_Empty_FailsWithPropertyRequiredError(string studentId)
     {
         // Arrange
-        StudentGroupCreateDto dto = new(studentId);
+        AssignStudentDto dto = new(studentId);
 
         // Act
         var result = await _validator.TestValidateAsync(dto);
@@ -49,7 +49,7 @@ public async Task StudentId_Empty_FailsWithPropertyRequiredError(string studentI
     public async Task StudentId_UserDoesNotExist_FailsWithInvalidForeignKeyError()
     {
         // Arrange
-        StudentGroupCreateDto dto = new(NonExistentUserId);
+        AssignStudentDto dto = new(NonExistentUserId);
 
         // Act
         var result = await _validator.TestValidateAsync(dto);
@@ -65,7 +65,7 @@ public async Task StudentId_UserDoesNotExist_FailsWithInvalidForeignKeyError()
     public async Task StudentId_UserWithoutStudentRole_FailsWithUserIsNotInRoleError(string userId)
     {
         // Arrange
-        StudentGroupCreateDto dto = new(userId);
+        AssignStudentDto dto = new(userId);
 
         // Act
         var result = await _validator.TestValidateAsync(dto);