Documentation/implementation-plan/assigning.md

Assigning Instructor / TA to a Course Section (Sprint 4)

Overview

This document describes the analysis and implementation plan for the admin API that allows assigning or removing an Instructor or Teaching Assistant (TA) for a specific course section.

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Problem Statement

Before this feature, there was no REST API for an admin to directly assign an instructor or TA to a course section.
The database tables (course_instructors, course_tas) and entities already existed but had no corresponding service methods or controller endpoints.

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Analysis

Existing Infrastructure

Component	Location	Status before Sprint 4
course_instructors table	DB	✅ Exists
course_tas table	DB	✅ Exists
CourseInstructor entity	src/modules/enrollments/entities/course-instructor.entity.ts	✅ Exists
CourseTA entity	src/modules/enrollments/entities/course-ta.entity.ts	✅ Exists
EnrollmentsService repositories	enrollments.service.ts lines 58–60	✅ Injected, unused
Service methods (assignInstructor, assignTA, …)	enrollments.service.ts	❌ Missing
Controller endpoints	enrollments.controller.ts	❌ Missing

Entity Schemas

course_instructors

Column	Type	Notes
assignment_id	bigint PK	Auto-increment
section_id	bigint FK	References course_sections
user_id	bigint FK	References users
role	enum	primary, co_instructor, guest
assigned_at	timestamp	Auto-set on insert

Unique constraint: (section_id, user_id) — one assignment per user per section.

course_tas

Column	Type	Notes
assignment_id	bigint PK	Auto-increment
user_id	bigint FK	References users
section_id	bigint FK	References course_sections
responsibilities	text	Optional TA duties description
assigned_at	timestamp	Auto-set on insert

Unique constraint: (section_id, user_id) — one TA assignment per user per section.

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Implementation

New Files

File	Purpose
src/modules/enrollments/dto/assign-instructor.dto.ts	AssignInstructorDto, InstructorAssignmentResponseDto
src/modules/enrollments/dto/assign-ta.dto.ts	AssignTADto, TAAssignmentResponseDto

Modified Files

File	Changes
src/modules/enrollments/dto/index.ts	Exported new DTOs
src/modules/enrollments/exceptions/index.ts	Added 6 new exception classes
src/modules/enrollments/services/enrollments.service.ts	Added 6 new public methods
src/modules/enrollments/controllers/enrollments.controller.ts	Added 6 new endpoints

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API Endpoints

All endpoints are under the base path /api/enrollments and require JWT Bearer authentication.

Instructor Assignment

Assign Instructor to Section

POST /api/enrollments/sections/:sectionId/instructors

• Auth: Bearer JWT
• Roles: admin
• Request Body:

  {
    "userId": 5,
    "role": "primary"
  }
  

  • userId (required) – ID of the user to assign
  • role (optional, default: primary) – primary | co_instructor | guest
• Success: 201 Created → InstructorAssignmentResponseDto
• Errors: 404 section/user not found, 409 already assigned

Remove Instructor from Section

DELETE /api/enrollments/sections/:sectionId/instructors/:assignmentId

• Auth: Bearer JWT
• Roles: admin
• Success: 204 No Content
• Errors: 404 section/assignment not found

List Section Instructors

GET /api/enrollments/sections/:sectionId/instructors

• Auth: Bearer JWT
• Roles: admin, instructor
• Success: 200 OK → InstructorAssignmentResponseDto[]
• Errors: 404 section not found

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TA Assignment

Assign TA to Section

POST /api/enrollments/sections/:sectionId/tas

• Auth: Bearer JWT
• Roles: admin
• Request Body:

  {
    "userId": 7,
    "responsibilities": "Grading assignments, office hours Mon/Wed"
  }
  

  • userId (required) – ID of the user to assign
  • responsibilities (optional) – free-text description of TA duties
• Success: 201 Created → TAAssignmentResponseDto
• Errors: 404 section/user not found, 409 already assigned

Remove TA from Section

DELETE /api/enrollments/sections/:sectionId/tas/:assignmentId

• Auth: Bearer JWT
• Roles: admin
• Success: 204 No Content
• Errors: 404 section/assignment not found

List Section TAs

GET /api/enrollments/sections/:sectionId/tas

• Auth: Bearer JWT
• Roles: admin, instructor
• Success: 200 OK → TAAssignmentResponseDto[]
• Errors: 404 section not found

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Response Shapes

InstructorAssignmentResponseDto

{
  "id": 1,
  "sectionId": 10,
  "userId": 5,
  "role": "primary",
  "assignedAt": "2026-03-11T20:00:00.000Z",
  "firstName": "John",
  "lastName": "Doe",
  "email": "john.doe@example.com"
}

TAAssignmentResponseDto

{
  "id": 2,
  "sectionId": 10,
  "userId": 7,
  "responsibilities": "Grading assignments, office hours Mon/Wed",
  "assignedAt": "2026-03-11T20:00:00.000Z",
  "firstName": "Jane",
  "lastName": "Smith",
  "email": "jane.smith@example.com"
}

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New Exception Classes

Class	HTTP Status	Message
SectionNotFoundException	404	Section with id {id} not found
UserNotFoundException	404	User with id {id} not found
InstructorAlreadyAssignedException	409	This user is already assigned as an instructor for this section
InstructorAssignmentNotFoundException	404	Instructor assignment not found
TAAlreadyAssignedException	409	This user is already assigned as a Teaching Assistant for this section
TAAssignmentNotFoundException	404	Teaching Assistant assignment not found

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Access Control Summary

Endpoint	Admin	Instructor	TA	Student
POST sections/:id/instructors	✅	❌	❌	❌
DELETE sections/:id/instructors/:aid	✅	❌	❌	❌
GET sections/:id/instructors	✅	✅	❌	❌
POST sections/:id/tas	✅	❌	❌	❌
DELETE sections/:id/tas/:aid	✅	❌	❌	❌
GET sections/:id/tas	✅	✅	❌	❌

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Notes

• No database migrations are required — the tables already exist.
• The TypeORM synchronize: false setting means the schema is managed manually. No changes needed.
• The existing buildEnrollmentResponse() method in enrollments.service.ts has the instructor-loading query commented out (// temporarily disabled). Once sections consistently have instructors assigned via this API, that code can be re-enabled.