Make Separate Get Methods for Subentities (#47)

* Add `EnrollmentDate` property to`StudentGroup`

* Introduce `StudentGroupViewDto`

* Add `IAssigningService.GetAssigningEntitiesPageAsync<TViewDto>`

* Implement `GetAssigningEntitiesPageAsync`

* Extend integration tests for assigning endpoints

* Fix tests

* Implement GET methods for assigned entities

* Enhance fake data generation for `StudentGroup`

Core/Dtos/University/StudentGroupViewDto.cs

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

Core/Models/University/StudentGroup.cs

@@ -11,6 +11,11 @@ public class StudentGroup : IEntity<int>
     [Key]
     public int Id { get; set; }
 
+    /// <summary>
+    /// Date when student was added to the group.
+    /// </summary>
+    public DateTimeOffset EnrollmentDate { get; set; }
+
     /// <summary>
     /// Foreign key of the associated student.
     /// </summary>

Core/Services/IAssigningService.cs

@@ -1,4 +1,6 @@
-using System.Linq.Expressions;
+using EUniversity.Core.Filters;
+using EUniversity.Core.Pagination;
+using System.Linq.Expressions;
 
 namespace EUniversity.Core.Services;
 
@@ -25,6 +27,19 @@ public interface IAssigningService<TAssigningEntity, TId1, TId2>
     /// </returns>
     public Expression<Func<TAssigningEntity, bool>> AssigningEntityPredicate(TId1 id1, TId2 id2);
 
+    /// <summary>
+    /// Retrieves a page with assigning entities DTOs asynchronously.
+    /// </summary>
+    /// <param name="id1">ID of the entity for which assigned entities should be returned.</param>
+    /// <param name="properties"><see cref="PaginationProperties"/> object specifying pagination parameters.</param>
+    /// <param name="filter">An optional filter to apply.</param>
+    /// <returns>
+    /// A task that represents the asynchronous operation, containing 
+    /// the page with assigning entities DTOs asynchronously.
+    /// </returns>
+    /// <typeparam name="TViewDto">A type of the DTO to which entities will be mapped.</typeparam>
+    public Task<Page<TViewDto>> GetAssigningEntitiesPageAsync<TViewDto>(TId1 id1, PaginationProperties properties, IFilter<TAssigningEntity>? filter = null);
+
     /// <summary>
     /// Adds the first entity to the second based on their IDs.
     /// </summary>

EUniversity/Controllers/University/GroupsController.cs

@@ -6,6 +6,7 @@
 using EUniversity.Core.Policy;
 using EUniversity.Core.Services;
 using EUniversity.Core.Services.University;
+using EUniversity.Infrastructure.Services.University;
 using Mapster;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
@@ -141,6 +142,37 @@ public async Task<IActionResult> DeleteGroupAsync([FromRoute] int id)
         return result ? NoContent() : NotFound();
     }
 
+    /// <summary>
+    /// Gets a page with all students that are part of the group with the given ID.
+    /// </summary>
+    /// <remarks>
+    /// If there is no items in the requested page, then empty page will be returned.
+    /// </remarks>
+    /// <response code="200">Returns requested page with students that are part of the group.</response>
+    /// <response code="400">Bad request</response>
+    /// <response code="401">Unauthorized user call</response>
+    /// <response code="404">Group does not exist</response>
+    [HttpGet]
+    [Route("{groupId:int}/students")]
+    [Authorize(Policies.Default)]
+    [ProducesResponseType(typeof(Page<StudentGroupViewDto>), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> GetStudentsInGroupAsync(
+        [FromRoute] int groupId,
+        [FromQuery] PaginationProperties properties)
+    {
+        if (!await _existenceChecker.ExistsAsync<Group, int>(groupId))
+        {
+            return NotFound(
+                CustomResponses.NotFound("The group with the specified ID does not exist.",
+                HttpContext));
+        }
+        return Ok(await _studentGroupsService
+            .GetAssigningEntitiesPageAsync<StudentGroupViewDto>(groupId, properties));
+    }
+
     /// <summary>
     /// Adds a student to a group.
     /// </summary>

EUniversity/Controllers/University/SemestersController.cs

@@ -10,6 +10,7 @@
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using SharpGrip.FluentValidation.AutoValidation.Mvc.Attributes;
+using System.Text.RegularExpressions;
 
 namespace EUniversity.Controllers.University;
 
@@ -141,6 +142,36 @@ public async Task<IActionResult> DeleteSemesterAsync([FromRoute] int id)
         return result ? NoContent() : NotFound();
     }
 
+    /// <summary>
+    /// Gets a page with all students related to the semester with the given ID.
+    /// </summary>
+    /// <remarks>
+    /// If there is no items in the requested page, then empty page will be returned.
+    /// </remarks>
+    /// <response code="200">Returns requested page with students related to the semester.</response>
+    /// <response code="400">Bad request</response>
+    /// <response code="401">Unauthorized user call</response>
+    [HttpGet]
+    [Route("{semesterId:int}/students")]
+    [Authorize(Policies.Default)]
+    [ProducesResponseType(typeof(Page<StudentSemesterViewDto>), StatusCodes.Status200OK)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status401Unauthorized)]
+    [ProducesResponseType(StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> GetStudentsInSemesterAsync(
+        [FromRoute] int semesterId,
+        [FromQuery] PaginationProperties properties)
+    {
+        if (!await _existenceChecker.ExistsAsync<Semester, int>(semesterId))
+        {
+            return NotFound(
+                CustomResponses.NotFound("The semester with the specified ID does not exist.",
+                HttpContext));
+        }
+        return Ok(await _studentSemestersService
+            .GetAssigningEntitiesPageAsync<StudentSemesterViewDto>(semesterId, properties));
+    }
+
     /// <summary>
     /// Adds a student to a semester.
     /// </summary>