Merge branch 'dev' into feat/frontend-controllers-adriaan

backend/.env.staging

@@ -0,0 +1,21 @@
+PORT=3000
+DWENGO_DB_HOST=db
+DWENGO_DB_PORT=5432
+DWENGO_DB_USERNAME=postgres
+DWENGO_DB_PASSWORD=postgres
+DWENGO_DB_UPDATE=false
+
+DWENGO_AUTH_STUDENT_URL=http://localhost/idp/realms/student
+DWENGO_AUTH_STUDENT_CLIENT_ID=dwengo
+DWENGO_AUTH_STUDENT_JWKS_ENDPOINT=http://idp:7080/idp/realms/student/protocol/openid-connect/certs
+DWENGO_AUTH_TEACHER_URL=http://localhost/idp/realms/teacher
+DWENGO_AUTH_TEACHER_CLIENT_ID=dwengo
+DWENGO_AUTH_TEACHER_JWKS_ENDPOINT=http://idp:7080/idp/realms/teacher/protocol/openid-connect/certs
+
+# Allow Vite dev-server to access the backend (for testing purposes). Don't forget to remove this in production!
+#DWENGO_CORS_ALLOWED_ORIGINS=http://localhost/,127.0.0.1:80,http://127.0.0.1,http://localhost:80,http://127.0.0.1:80,localhost
+DWENGO_CORS_ALLOWED_ORIGINS=http://localhost/*,http://idp:7080,https://idp:7080
+
+# Logging and monitoring
+
+LOKI_HOST=http://logging:3102

backend/.env.test

@@ -1,3 +1,13 @@
-PORT=3000
-DWENGO_DB_UPDATE=true
+#
+# Test environment configuration
+#
+# Should not need to be modified.
+# See .env.example for more information.
+#
+
+### Dwengo ###
+
+DWENGO_PORT=3000
+
 DWENGO_DB_NAME=":memory:"
+DWENGO_DB_UPDATE=true

backend/.env.test.example

@@ -1,13 +0,0 @@
-#
-# Test environment configuration
-#
-# Should not need to be modified.
-# See .env.example for more information.
-#
-
-### Dwengo ###
-
-DWENGO_PORT=3000
-
-DWENGO_DB_NAME=":memory:"
-DWENGO_DB_UPDATE=true

backend/Dockerfile

@@ -1,38 +1,51 @@
 FROM node:22 AS build-stage
 
-WORKDIR /app
+WORKDIR /app/dwengo
 
 # Install dependencies
 
 COPY package*.json ./
 COPY backend/package.json ./backend/
+# Backend depends on common
+COPY common/package.json ./common/
 
 RUN npm install --silent
 
 # Build the backend
 
 # Root tsconfig.json
-COPY tsconfig.json ./
+COPY tsconfig.json tsconfig.build.json ./
 
-WORKDIR /app/backend
-
-COPY backend ./
-COPY docs /app/docs
+COPY backend ./backend
+COPY common ./common
+COPY docs ./docs
 
 RUN npm run build
 
 FROM node:22 AS production-stage
 
-WORKDIR /app
+WORKDIR /app/dwengo
 
-COPY package-lock.json backend/package.json ./
+# Copy static files
+
+COPY ./backend/i18n ./i18n
+
+# Copy built files
+
+COPY --from=build-stage /app/dwengo/common/dist ./common/dist
+COPY --from=build-stage /app/dwengo/backend/dist ./backend/dist
+
+COPY package*.json ./
+COPY backend/package.json ./backend/
+# Backend depends on common
+COPY common/package.json ./common/
 
 RUN npm install --silent --only=production
 
-COPY ./docs /docs
-COPY ./backend/i18n /app/i18n
-COPY --from=build-stage /app/backend/dist ./dist/
+COPY ./docs ./docs
+COPY ./backend/i18n ./backend/i18n
+COPY ./backend/.env ./backend/.env
 
 EXPOSE 3000
 
-CMD ["node", "--env-file=.env", "dist/app.js"]
+CMD ["node", "--env-file=/app/dwengo/backend/.env", "/app/dwengo/backend/dist/app.js"]

backend/README.md

@@ -34,7 +34,9 @@ npm run test:unit
 
 ```shell
 # Omgevingsvariabelen
-cp .env.development.example .env
+cp .env.example .env
+# Configureer de .env file met de juiste waarden!
+nano .env
 
 npm run build
 npm run start

backend/config.js

@@ -1,7 +0,0 @@
-// Can be placed in dotenv but found it redundant
-// Import dotenv from "dotenv";
-// Load .env file
-// Dotenv.config();
-export const DWENGO_API_BASE = 'https://dwengo.org/backend/api';
-export const FALLBACK_LANG = 'nl';
-export const FALLBACK_SEQ_NUM = 1;

backend/eslint.config.ts

@@ -8,14 +8,4 @@ export default [
             globals: globals.node,
         },
     },
-
-    {
-        files: ['tests/**/*.ts'],
-        languageOptions: {
-            globals: globals.node,
-        },
-        rules: {
-            'no-console': 'off',
-        },
-    },
 ];

backend/package.json

@@ -1,17 +1,19 @@
 {
-    "name": "dwengo-1-backend",
+    "name": "@dwengo-1/backend",
     "version": "0.1.1",
     "description": "Backend for Dwengo-1",
     "private": true,
     "type": "module",
+    "main": "dist/app.js",
     "scripts": {
-        "build": "cross-env NODE_ENV=production tsc --project tsconfig.json",
+        "build": "cross-env NODE_ENV=production tsc --build",
         "dev": "cross-env NODE_ENV=development tsx watch --env-file=.env.development.local src/app.ts",
         "start": "cross-env NODE_ENV=production node --env-file=.env dist/app.js",
         "format": "prettier --write src/",
         "format-check": "prettier --check src/",
         "lint": "eslint . --fix",
-        "test:unit": "vitest"
+        "pretest:unit": "npm run build",
+        "test:unit": "vitest --run"
     },
     "dependencies": {
         "@mikro-orm/core": "6.4.9",
@@ -24,6 +26,7 @@
         "cross": "^1.0.0",
         "cross-env": "^7.0.3",
         "dotenv": "^16.4.7",
+        "dwengo-1-common": "^0.1.1",
         "express": "^5.0.1",
         "express-jwt": "^8.5.1",
         "gift-pegjs": "^1.0.2",

backend/src/app.ts

@@ -5,15 +5,16 @@ import cors from './middleware/cors.js';
 import { getLogger, Logger } from './logging/initalize.js';
 import { responseTimeLogger } from './logging/responseTimeLogger.js';
 import responseTime from 'response-time';
-import { EnvVars, getNumericEnvVar } from './util/envvars.js';
+import { envVars, getNumericEnvVar } from './util/envVars.js';
 import apiRouter from './routes/router.js';
 import swaggerMiddleware from './swagger.js';
 import swaggerUi from 'swagger-ui-express';
+import { errorHandler } from './middleware/error-handling/error-handler.js';
 
 const logger: Logger = getLogger();
 
 const app: Express = express();
-const port: string | number = getNumericEnvVar(EnvVars.Port);
+const port: string | number = getNumericEnvVar(envVars.Port);
 
 app.use(express.json());
 app.use(cors);
@@ -26,7 +27,9 @@ app.use('/api', apiRouter);
 // Swagger
 app.use('/api-docs', swaggerUi.serve, swaggerMiddleware);
 
-async function startServer() {
+app.use(errorHandler);
+
+async function startServer(): Promise<void> {
     await initORM();
 
     app.listen(port, () => {

backend/src/config.ts

@@ -1,7 +1,7 @@
-import { EnvVars, getEnvVar } from './util/envvars.js';
+import { envVars, getEnvVar } from './util/envVars.js';
 
 // API
-export const DWENGO_API_BASE = getEnvVar(EnvVars.LearningContentRepoApiBaseUrl);
-export const FALLBACK_LANG = getEnvVar(EnvVars.FallbackLanguage);
+export const DWENGO_API_BASE = getEnvVar(envVars.LearningContentRepoApiBaseUrl);
+export const FALLBACK_LANG = getEnvVar(envVars.FallbackLanguage);
 
 export const FALLBACK_SEQ_NUM = 1;

backend/src/controllers/assignments.ts

@@ -1,8 +1,8 @@
 import { Request, Response } from 'express';
 import { createAssignment, getAllAssignments, getAssignment, getAssignmentsSubmissions } from '../services/assignments.js';
-import { AssignmentDTO } from '../interfaces/assignment.js';
+import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
 
-// Typescript is annoy with with parameter forwarding from class.ts
+// Typescript is annoying with parameter forwarding from class.ts
 interface AssignmentParams {
     classid: string;
     id: string;
@@ -41,7 +41,7 @@ export async function createAssignmentHandler(req: Request<AssignmentParams>, re
 }
 
 export async function getAssignmentHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
-    const id = +req.params.id;
+    const id = Number(req.params.id);
     const classid = req.params.classid;
 
     if (isNaN(id)) {
@@ -61,7 +61,7 @@ export async function getAssignmentHandler(req: Request<AssignmentParams>, res:
 
 export async function getAssignmentsSubmissionsHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
     const classid = req.params.classid;
-    const assignmentNumber = +req.params.id;
+    const assignmentNumber = Number(req.params.id);
     const full = req.query.full === 'true';
 
     if (isNaN(assignmentNumber)) {

backend/src/controllers/auth.ts

@@ -1,16 +1,16 @@
-import { EnvVars, getEnvVar } from '../util/envvars.js';
+import { envVars, getEnvVar } from '../util/envVars.js';
 
-type FrontendIdpConfig = {
+interface FrontendIdpConfig {
     authority: string;
     clientId: string;
     scope: string;
     responseType: string;
-};
+}
 
-type FrontendAuthConfig = {
+interface FrontendAuthConfig {
     student: FrontendIdpConfig;
     teacher: FrontendIdpConfig;
-};
+}
 
 const SCOPE = 'openid profile email';
 const RESPONSE_TYPE = 'code';
@@ -18,14 +18,14 @@ const RESPONSE_TYPE = 'code';
 export function getFrontendAuthConfig(): FrontendAuthConfig {
     return {
         student: {
-            authority: getEnvVar(EnvVars.IdpStudentUrl),
-            clientId: getEnvVar(EnvVars.IdpStudentClientId),
+            authority: getEnvVar(envVars.IdpStudentUrl),
+            clientId: getEnvVar(envVars.IdpStudentClientId),
             scope: SCOPE,
             responseType: RESPONSE_TYPE,
         },
         teacher: {
-            authority: getEnvVar(EnvVars.IdpTeacherUrl),
-            clientId: getEnvVar(EnvVars.IdpTeacherClientId),
+            authority: getEnvVar(envVars.IdpTeacherUrl),
+            clientId: getEnvVar(envVars.IdpTeacherClientId),
             scope: SCOPE,
             responseType: RESPONSE_TYPE,
         },

backend/src/controllers/classes.ts

@@ -1,6 +1,6 @@
 import { Request, Response } from 'express';
 import { createClass, getAllClasses, getClass, getClassStudents, getClassStudentsIds, getClassTeacherInvitations } from '../services/classes.js';
-import { ClassDTO } from '../interfaces/class.js';
+import { ClassDTO } from '@dwengo-1/common/interfaces/class';
 
 export async function getAllClassesHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';

backend/src/controllers/error-helper.ts

@@ -0,0 +1,18 @@
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+
+/**
+ * Checks for the presence of required fields and throws a BadRequestException
+ * if any are missing.
+ *
+ * @param fields - An object with key-value pairs to validate.
+ */
+export function requireFields(fields: Record<string, unknown>): void {
+    const missing = Object.entries(fields)
+        .filter(([_, value]) => value === undefined || value === null || value === '')
+        .map(([key]) => key);
+
+    if (missing.length > 0) {
+        const message = `Missing required field${missing.length > 1 ? 's' : ''}: ${missing.join(', ')}`;
+        throw new BadRequestException(message);
+    }
+}

backend/src/controllers/groups.ts

@@ -1,6 +1,6 @@
 import { Request, Response } from 'express';
 import { createGroup, getAllGroups, getGroup, getGroupSubmissions } from '../services/groups.js';
-import { GroupDTO } from '../interfaces/group.js';
+import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 
 // Typescript is annoywith with parameter forwarding from class.ts
 interface GroupParams {
@@ -12,14 +12,14 @@ interface GroupParams {
 export async function getGroupHandler(req: Request<GroupParams>, res: Response): Promise<void> {
     const classId = req.params.classid;
     const full = req.query.full === 'true';
-    const assignmentId = +req.params.assignmentid;
+    const assignmentId = Number(req.params.assignmentid);
 
     if (isNaN(assignmentId)) {
         res.status(400).json({ error: 'Assignment id must be a number' });
         return;
     }
 
-    const groupId = +req.params.groupid!; // Can't be undefined
+    const groupId = Number(req.params.groupid!); // Can't be undefined
 
     if (isNaN(groupId)) {
         res.status(400).json({ error: 'Group id must be a number' });
@@ -40,7 +40,7 @@ export async function getAllGroupsHandler(req: Request, res: Response): Promise<
     const classId = req.params.classid;
     const full = req.query.full === 'true';
 
-    const assignmentId = +req.params.assignmentid;
+    const assignmentId = Number(req.params.assignmentid);
 
     if (isNaN(assignmentId)) {
         res.status(400).json({ error: 'Assignment id must be a number' });
@@ -56,7 +56,7 @@ export async function getAllGroupsHandler(req: Request, res: Response): Promise<
 
 export async function createGroupHandler(req: Request, res: Response): Promise<void> {
     const classid = req.params.classid;
-    const assignmentId = +req.params.assignmentid;
+    const assignmentId = Number(req.params.assignmentid);
 
     if (isNaN(assignmentId)) {
         res.status(400).json({ error: 'Assignment id must be a number' });
@@ -78,14 +78,14 @@ export async function getGroupSubmissionsHandler(req: Request, res: Response): P
     const classId = req.params.classid;
     const full = req.query.full === 'true';
 
-    const assignmentId = +req.params.assignmentid;
+    const assignmentId = Number(req.params.assignmentid);
 
     if (isNaN(assignmentId)) {
         res.status(400).json({ error: 'Assignment id must be a number' });
         return;
     }
 
-    const groupId = +req.params.groupid!; // Can't be undefined
+    const groupId = Number(req.params.groupid); // Can't be undefined
 
     if (isNaN(groupId)) {
         res.status(400).json({ error: 'Group id must be a number' });

backend/src/controllers/learning-objects.ts

@@ -1,20 +1,20 @@
 import { Request, Response } from 'express';
 import { FALLBACK_LANG } from '../config.js';
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../interfaces/learning-content.js';
 import learningObjectService from '../services/learning-objects/learning-object-service.js';
-import { EnvVars, getEnvVar } from '../util/envvars.js';
-import { Language } from '../entities/content/language.js';
-import { BadRequestException } from '../exceptions.js';
+import { Language } from '@dwengo-1/common/util/language';
 import attachmentService from '../services/learning-objects/attachment-service.js';
-import { NotFoundError } from '@mikro-orm/core';
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { envVars, getEnvVar } from '../util/envVars.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
 function getLearningObjectIdentifierFromRequest(req: Request): LearningObjectIdentifier {
     if (!req.params.hruid) {
         throw new BadRequestException('HRUID is required.');
     }
     return {
-        hruid: req.params.hruid as string,
-        language: (req.query.language || getEnvVar(EnvVars.FallbackLanguage)) as Language,
+        hruid: req.params.hruid,
+        language: (req.query.language || getEnvVar(envVars.FallbackLanguage)) as Language,
         version: parseInt(req.query.version as string),
     };
 }
@@ -24,7 +24,7 @@ function getLearningPathIdentifierFromRequest(req: Request): LearningPathIdentif
         throw new BadRequestException('HRUID is required.');
     }
     return {
-        hruid: req.params.hruid as string,
+        hruid: req.params.hruid,
         language: (req.query.language as Language) || FALLBACK_LANG,
     };
 }
@@ -47,6 +47,11 @@ export async function getLearningObject(req: Request, res: Response): Promise<vo
     const learningObjectId = getLearningObjectIdentifierFromRequest(req);
 
     const learningObject = await learningObjectService.getLearningObjectById(learningObjectId);
+
+    if (!learningObject) {
+        throw new NotFoundException('Learning object not found');
+    }
+
     res.json(learningObject);
 }
 
@@ -63,7 +68,7 @@ export async function getAttachment(req: Request, res: Response): Promise<void>
     const attachment = await attachmentService.getAttachment(learningObjectId, name);
 
     if (!attachment) {
-        throw new NotFoundError(`Attachment ${name} not found`);
+        throw new NotFoundException(`Attachment ${name} not found`);
     }
     res.setHeader('Content-Type', attachment.mimeType).send(attachment.content);
 }

backend/src/controllers/learning-paths.ts

@@ -2,13 +2,14 @@ import { Request, Response } from 'express';
 import { themes } from '../data/themes.js';
 import { FALLBACK_LANG } from '../config.js';
 import learningPathService from '../services/learning-paths/learning-path-service.js';
-import { BadRequestException, NotFoundException } from '../exceptions.js';
-import { Language } from '../entities/content/language.js';
+import { Language } from '@dwengo-1/common/util/language';
 import {
     PersonalizationTarget,
     personalizedForGroup,
     personalizedForStudent,
 } from '../services/learning-paths/learning-path-personalization-util.js';
+import { BadRequestException } from '../exceptions/bad-request-exception.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
 
 /**
  * Fetch learning paths based on query parameters.

backend/src/controllers/questions.ts

@@ -1,9 +1,9 @@
 import { Request, Response } from 'express';
 import { createQuestion, deleteQuestion, getAllQuestions, getAnswersByQuestion, getQuestion } from '../services/questions.js';
-import { QuestionDTO, QuestionId } from '../interfaces/question.js';
 import { FALLBACK_LANG, FALLBACK_SEQ_NUM } from '../config.js';
 import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
-import { Language } from '../entities/content/language.js';
+import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
+import { Language } from '@dwengo-1/common/util/language';
 
 function getObjectId(req: Request, res: Response): LearningObjectIdentifier | null {
     const { hruid, version } = req.params;
@@ -17,7 +17,7 @@ function getObjectId(req: Request, res: Response): LearningObjectIdentifier | nu
     return {
         hruid,
         language: (lang as Language) || FALLBACK_LANG,
-        version: +version,
+        version: Number(version),
     };
 }
 

backend/src/controllers/students.ts

@@ -1,101 +1,67 @@
 import { Request, Response } from 'express';
 import {
+    createClassJoinRequest,
     createStudent,
+    deleteClassJoinRequest,
     deleteStudent,
     getAllStudents,
+    getJoinRequestByStudentClass,
+    getJoinRequestsByStudent,
     getStudent,
     getStudentAssignments,
     getStudentClasses,
     getStudentGroups,
+    getStudentQuestions,
     getStudentSubmissions,
 } from '../services/students.js';
-import { StudentDTO } from '../interfaces/student.js';
+import { requireFields } from './error-helper.js';
+import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 
-// TODO: accept arguments (full, ...)
-// TODO: endpoints
 export async function getAllStudentsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
 
-    const students = await getAllStudents(full);
+    const students: StudentDTO[] | string[] = await getAllStudents(full);
 
-    if (!students) {
-        res.status(404).json({ error: `Student not found.` });
-        return;
-    }
-
-    res.json({ students: students });
+    res.json({ students });
 }
 
 export async function getStudentHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const student = await getStudent(username);
 
-    const user = await getStudent(username);
-
-    if (!user) {
-        res.status(404).json({
-            error: `User with username '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.json(user);
+    res.json({ student });
 }
 
-export async function createStudentHandler(req: Request, res: Response) {
+export async function createStudentHandler(req: Request, res: Response): Promise<void> {
+    const username = req.body.username;
+    const firstName = req.body.firstName;
+    const lastName = req.body.lastName;
+    requireFields({ username, firstName, lastName });
+
     const userData = req.body as StudentDTO;
 
-    if (!userData.username || !userData.firstName || !userData.lastName) {
-        res.status(400).json({
-            error: 'Missing required fields: username, firstName, lastName',
-        });
-        return;
-    }
-
-    const newUser = await createStudent(userData);
-
-    if (!newUser) {
-        res.status(500).json({
-            error: 'Something went wrong while creating student',
-        });
-        return;
-    }
-
-    res.status(201).json(newUser);
+    const student = await createStudent(userData);
+    res.json({ student });
 }
 
-export async function deleteStudentHandler(req: Request, res: Response) {
+export async function deleteStudentHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
-
-    const deletedUser = await deleteStudent(username);
-    if (!deletedUser) {
-        res.status(404).json({
-            error: `User with username '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.status(200).json(deletedUser);
+    const student = await deleteStudent(username);
+    res.json({ student });
 }
 
 export async function getStudentClassesHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const classes = await getStudentClasses(username, full);
 
-    res.json({
-        classes: classes,
-    });
+    res.json({ classes });
 }
 
 // TODO
@@ -104,33 +70,75 @@ export async function getStudentClassesHandler(req: Request, res: Response): Pro
 // Have this assignment.
 export async function getStudentAssignmentsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const assignments = getStudentAssignments(username, full);
 
-    res.json({
-        assignments: assignments,
-    });
+    res.json({ assignments });
 }
 
 export async function getStudentGroupsHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
-    const username = req.params.id;
+    const username = req.params.username;
+    requireFields({ username });
 
     const groups = await getStudentGroups(username, full);
 
-    res.json({
-        groups: groups,
-    });
+    res.json({ groups });
 }
 
 export async function getStudentSubmissionsHandler(req: Request, res: Response): Promise<void> {
-    const username = req.params.id;
+    const username = req.params.username;
     const full = req.query.full === 'true';
+    requireFields({ username });
 
     const submissions = await getStudentSubmissions(username, full);
 
-    res.json({
-        submissions: submissions,
-    });
+    res.json({ submissions });
+}
+
+export async function getStudentQuestionsHandler(req: Request, res: Response): Promise<void> {
+    const full = req.query.full === 'true';
+    const username = req.params.username;
+    requireFields({ username });
+
+    const questions = await getStudentQuestions(username, full);
+
+    res.json({ questions });
+}
+
+export async function createStudentRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.body.classId;
+    requireFields({ username, classId });
+
+    const request = await createClassJoinRequest(username, classId);
+    res.json({ request });
+}
+
+export async function getStudentRequestsHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    requireFields({ username });
+
+    const requests = await getJoinRequestsByStudent(username);
+    res.json({ requests });
+}
+
+export async function getStudentRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const request = await getJoinRequestByStudentClass(username, classId);
+    res.json({ request });
+}
+
+export async function deleteClassJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.params.username;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const request = await deleteClassJoinRequest(username, classId);
+    res.json({ request });
 }

backend/src/controllers/submissions.ts

@@ -1,7 +1,7 @@
 import { Request, Response } from 'express';
 import { createSubmission, deleteSubmission, getSubmission } from '../services/submissions.js';
-import { Language, languageMap } from '../entities/content/language.js';
-import { SubmissionDTO } from '../interfaces/submission';
+import { SubmissionDTO } from '@dwengo-1/common/interfaces/submission';
+import { Language, languageMap } from '@dwengo-1/common/util/language';
 
 interface SubmissionParams {
     hruid: string;
@@ -10,7 +10,7 @@ interface SubmissionParams {
 
 export async function getSubmissionHandler(req: Request<SubmissionParams>, res: Response): Promise<void> {
     const lohruid = req.params.hruid;
-    const submissionNumber = +req.params.id;
+    const submissionNumber = Number(req.params.id);
 
     if (isNaN(submissionNumber)) {
         res.status(400).json({ error: 'Submission number is not a number' });
@@ -30,7 +30,7 @@ export async function getSubmissionHandler(req: Request<SubmissionParams>, res:
     res.json(submission);
 }
 
-export async function createSubmissionHandler(req: Request, res: Response) {
+export async function createSubmissionHandler(req: Request, res: Response): Promise<void> {
     const submissionDTO = req.body as SubmissionDTO;
 
     const submission = await createSubmission(submissionDTO);
@@ -43,9 +43,9 @@ export async function createSubmissionHandler(req: Request, res: Response) {
     res.json(submission);
 }
 
-export async function deleteSubmissionHandler(req: Request, res: Response) {
+export async function deleteSubmissionHandler(req: Request, res: Response): Promise<void> {
     const hruid = req.params.hruid;
-    const submissionNumber = +req.params.id;
+    const submissionNumber = Number(req.params.id);
 
     const lang = languageMap[req.query.language as string] || Language.Dutch;
     const version = (req.query.version || 1) as number;

backend/src/controllers/teachers.ts

@@ -4,137 +4,97 @@ import {
     deleteTeacher,
     getAllTeachers,
     getClassesByTeacher,
-    getQuestionsByTeacher,
+    getJoinRequestsByClass,
     getStudentsByTeacher,
     getTeacher,
+    getTeacherQuestions,
+    updateClassJoinRequestStatus,
 } from '../services/teachers.js';
-import { TeacherDTO } from '../interfaces/teacher.js';
+import { requireFields } from './error-helper.js';
+import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
 
 export async function getAllTeachersHandler(req: Request, res: Response): Promise<void> {
     const full = req.query.full === 'true';
 
-    const teachers = await getAllTeachers(full);
+    const teachers: TeacherDTO[] | string[] = await getAllTeachers(full);
 
-    if (!teachers) {
-        res.status(404).json({ error: `Teacher not found.` });
-        return;
-    }
-
-    res.json({ teachers: teachers });
+    res.json({ teachers });
 }
 
 export async function getTeacherHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const teacher = await getTeacher(username);
 
-    const user = await getTeacher(username);
-
-    if (!user) {
-        res.status(404).json({
-            error: `Teacher '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.json(user);
+    res.json({ teacher });
 }
 
-export async function createTeacherHandler(req: Request, res: Response) {
+export async function createTeacherHandler(req: Request, res: Response): Promise<void> {
+    const username = req.body.username;
+    const firstName = req.body.firstName;
+    const lastName = req.body.lastName;
+    requireFields({ username, firstName, lastName });
+
     const userData = req.body as TeacherDTO;
 
-    if (!userData.username || !userData.firstName || !userData.lastName) {
-        res.status(400).json({
-            error: 'Missing required fields: username, firstName, lastName',
-        });
-        return;
-    }
-
-    const newUser = await createTeacher(userData);
-
-    if (!newUser) {
-        res.status(400).json({ error: 'Failed to create teacher' });
-        return;
-    }
-
-    res.status(201).json(newUser);
+    const teacher = await createTeacher(userData);
+    res.json({ teacher });
 }
 
-export async function deleteTeacherHandler(req: Request, res: Response) {
+export async function deleteTeacherHandler(req: Request, res: Response): Promise<void> {
     const username = req.params.username;
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
-
-    const deletedUser = await deleteTeacher(username);
-    if (!deletedUser) {
-        res.status(404).json({
-            error: `User '${username}' not found.`,
-        });
-        return;
-    }
-
-    res.status(200).json(deletedUser);
+    const teacher = await deleteTeacher(username);
+    res.json({ teacher });
 }
 
 export async function getTeacherClassHandler(req: Request, res: Response): Promise<void> {
-    const username = req.params.username as string;
+    const username = req.params.username;
     const full = req.query.full === 'true';
-
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    requireFields({ username });
 
     const classes = await getClassesByTeacher(username, full);
 
-    if (!classes) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ classes: classes });
+    res.json({ classes });
 }
 
 export async function getTeacherStudentHandler(req: Request, res: Response): Promise<void> {
-    const username = req.params.username as string;
+    const username = req.params.username;
     const full = req.query.full === 'true';
-
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    requireFields({ username });
 
     const students = await getStudentsByTeacher(username, full);
 
-    if (!students) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ students: students });
+    res.json({ students });
 }
 
 export async function getTeacherQuestionHandler(req: Request, res: Response): Promise<void> {
-    const username = req.params.username as string;
+    const username = req.params.username;
     const full = req.query.full === 'true';
+    requireFields({ username });
 
-    if (!username) {
-        res.status(400).json({ error: 'Missing required field: username' });
-        return;
-    }
+    const questions = await getTeacherQuestions(username, full);
 
-    const questions = await getQuestionsByTeacher(username, full);
-
-    if (!questions) {
-        res.status(404).json({ error: 'Teacher not found' });
-        return;
-    }
-
-    res.json({ questions: questions });
+    res.json({ questions });
+}
+
+export async function getStudentJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const username = req.query.username as string;
+    const classId = req.params.classId;
+    requireFields({ username, classId });
+
+    const joinRequests = await getJoinRequestsByClass(classId);
+    res.json({ joinRequests });
+}
+
+export async function updateStudentJoinRequestHandler(req: Request, res: Response): Promise<void> {
+    const studentUsername = req.query.studentUsername as string;
+    const classId = req.params.classId;
+    const accepted = req.body.accepted !== 'false'; // Default = true
+    requireFields({ studentUsername, classId });
+
+    const request = await updateClassJoinRequestStatus(studentUsername, classId, accepted);
+    res.json({ request });
 }

backend/src/controllers/themes.ts

@@ -3,25 +3,23 @@ import { themes } from '../data/themes.js';
 import { loadTranslations } from '../util/translation-helper.js';
 
 interface Translations {
-    curricula_page: {
-        [key: string]: { title: string; description?: string };
-    };
+    curricula_page: Record<string, { title: string; description?: string }>;
 }
 
-export function getThemesHandler(req: Request, res: Response) {
-    const language = (req.query.language as string)?.toLowerCase() || 'nl';
+export function getThemesHandler(req: Request, res: Response): void {
+    const language = ((req.query.language as string) || 'nl').toLowerCase();
     const translations = loadTranslations<Translations>(language);
     const themeList = themes.map((theme) => ({
         key: theme.title,
-        title: translations.curricula_page[theme.title]?.title || theme.title,
-        description: translations.curricula_page[theme.title]?.description,
+        title: translations.curricula_page[theme.title].title || theme.title,
+        description: translations.curricula_page[theme.title].description,
         image: `https://dwengo.org/images/curricula/logo_${theme.title}.png`,
     }));
 
     res.json(themeList);
 }
 
-export function getHruidsByThemeHandler(req: Request, res: Response) {
+export function getHruidsByThemeHandler(req: Request, res: Response): void {
     const themeKey = req.params.theme;
 
     if (!themeKey) {

backend/src/data/assignments/assignment-repository.ts

@@ -3,13 +3,13 @@ import { Assignment } from '../../entities/assignments/assignment.entity.js';
 import { Class } from '../../entities/classes/class.entity.js';
 
 export class AssignmentRepository extends DwengoEntityRepository<Assignment> {
-    public findByClassAndId(within: Class, id: number): Promise<Assignment | null> {
+    public async findByClassAndId(within: Class, id: number): Promise<Assignment | null> {
         return this.findOne({ within: within, id: id });
     }
-    public findAllAssignmentsInClass(within: Class): Promise<Assignment[]> {
+    public async findAllAssignmentsInClass(within: Class): Promise<Assignment[]> {
         return this.findAll({ where: { within: within } });
     }
-    public deleteByClassAndId(within: Class, id: number): Promise<void> {
+    public async deleteByClassAndId(within: Class, id: number): Promise<void> {
         return this.deleteWhere({ within: within, id: id });
     }
 }

backend/src/data/assignments/group-repository.ts

@@ -4,7 +4,7 @@ import { Assignment } from '../../entities/assignments/assignment.entity.js';
 import { Student } from '../../entities/users/student.entity.js';
 
 export class GroupRepository extends DwengoEntityRepository<Group> {
-    public findByAssignmentAndGroupNumber(assignment: Assignment, groupNumber: number): Promise<Group | null> {
+    public async findByAssignmentAndGroupNumber(assignment: Assignment, groupNumber: number): Promise<Group | null> {
         return this.findOne(
             {
                 assignment: assignment,
@@ -13,16 +13,16 @@ export class GroupRepository extends DwengoEntityRepository<Group> {
             { populate: ['members'] }
         );
     }
-    public findAllGroupsForAssignment(assignment: Assignment): Promise<Group[]> {
+    public async findAllGroupsForAssignment(assignment: Assignment): Promise<Group[]> {
         return this.findAll({
             where: { assignment: assignment },
             populate: ['members'],
         });
     }
-    public findAllGroupsWithStudent(student: Student): Promise<Group[]> {
+    public async findAllGroupsWithStudent(student: Student): Promise<Group[]> {
         return this.find({ members: student }, { populate: ['members'] });
     }
-    public deleteByAssignmentAndGroupNumber(assignment: Assignment, groupNumber: number) {
+    public async deleteByAssignmentAndGroupNumber(assignment: Assignment, groupNumber: number): Promise<void> {
         return this.deleteWhere({
             assignment: assignment,
             groupNumber: groupNumber,

backend/src/data/assignments/submission-repository.ts

@@ -5,7 +5,10 @@ import { LearningObjectIdentifier } from '../../entities/content/learning-object
 import { Student } from '../../entities/users/student.entity.js';
 
 export class SubmissionRepository extends DwengoEntityRepository<Submission> {
-    public findSubmissionByLearningObjectAndSubmissionNumber(loId: LearningObjectIdentifier, submissionNumber: number): Promise<Submission | null> {
+    public async findSubmissionByLearningObjectAndSubmissionNumber(
+        loId: LearningObjectIdentifier,
+        submissionNumber: number
+    ): Promise<Submission | null> {
         return this.findOne({
             learningObjectHruid: loId.hruid,
             learningObjectLanguage: loId.language,
@@ -14,7 +17,7 @@ export class SubmissionRepository extends DwengoEntityRepository<Submission> {
         });
     }
 
-    public findMostRecentSubmissionForStudent(loId: LearningObjectIdentifier, submitter: Student): Promise<Submission | null> {
+    public async findMostRecentSubmissionForStudent(loId: LearningObjectIdentifier, submitter: Student): Promise<Submission | null> {
         return this.findOne(
             {
                 learningObjectHruid: loId.hruid,
@@ -26,7 +29,7 @@ export class SubmissionRepository extends DwengoEntityRepository<Submission> {
         );
     }
 
-    public findMostRecentSubmissionForGroup(loId: LearningObjectIdentifier, group: Group): Promise<Submission | null> {
+    public async findMostRecentSubmissionForGroup(loId: LearningObjectIdentifier, group: Group): Promise<Submission | null> {
         return this.findOne(
             {
                 learningObjectHruid: loId.hruid,
@@ -38,15 +41,15 @@ export class SubmissionRepository extends DwengoEntityRepository<Submission> {
         );
     }
 
-    public findAllSubmissionsForGroup(group: Group): Promise<Submission[]> {
+    public async findAllSubmissionsForGroup(group: Group): Promise<Submission[]> {
         return this.find({ onBehalfOf: group });
     }
 
-    public findAllSubmissionsForStudent(student: Student): Promise<Submission[]> {
+    public async findAllSubmissionsForStudent(student: Student): Promise<Submission[]> {
         return this.find({ submitter: student });
     }
 
-    public deleteSubmissionByLearningObjectAndSubmissionNumber(loId: LearningObjectIdentifier, submissionNumber: number): Promise<void> {
+    public async deleteSubmissionByLearningObjectAndSubmissionNumber(loId: LearningObjectIdentifier, submissionNumber: number): Promise<void> {
         return this.deleteWhere({
             learningObjectHruid: loId.hruid,
             learningObjectLanguage: loId.language,

backend/src/data/classes/class-join-request-repository.ts

@@ -2,15 +2,19 @@ import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { Class } from '../../entities/classes/class.entity.js';
 import { ClassJoinRequest } from '../../entities/classes/class-join-request.entity.js';
 import { Student } from '../../entities/users/student.entity.js';
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
 
 export class ClassJoinRequestRepository extends DwengoEntityRepository<ClassJoinRequest> {
-    public findAllRequestsBy(requester: Student): Promise<ClassJoinRequest[]> {
+    public async findAllRequestsBy(requester: Student): Promise<ClassJoinRequest[]> {
         return this.findAll({ where: { requester: requester } });
     }
-    public findAllOpenRequestsTo(clazz: Class): Promise<ClassJoinRequest[]> {
-        return this.findAll({ where: { class: clazz } });
+    public async findAllOpenRequestsTo(clazz: Class): Promise<ClassJoinRequest[]> {
+        return this.findAll({ where: { class: clazz, status: ClassJoinRequestStatus.Open } }); // TODO check if works like this
     }
-    public deleteBy(requester: Student, clazz: Class): Promise<void> {
+    public async findByStudentAndClass(requester: Student, clazz: Class): Promise<ClassJoinRequest | null> {
+        return this.findOne({ requester, class: clazz });
+    }
+    public async deleteBy(requester: Student, clazz: Class): Promise<void> {
         return this.deleteWhere({ requester: requester, class: clazz });
     }
 }

backend/src/data/classes/class-repository.ts

@@ -4,20 +4,20 @@ import { Student } from '../../entities/users/student.entity.js';
 import { Teacher } from '../../entities/users/teacher.entity';
 
 export class ClassRepository extends DwengoEntityRepository<Class> {
-    public findById(id: string): Promise<Class | null> {
+    public async findById(id: string): Promise<Class | null> {
         return this.findOne({ classId: id }, { populate: ['students', 'teachers'] });
     }
-    public deleteById(id: string): Promise<void> {
+    public async deleteById(id: string): Promise<void> {
         return this.deleteWhere({ classId: id });
     }
-    public findByStudent(student: Student): Promise<Class[]> {
+    public async findByStudent(student: Student): Promise<Class[]> {
         return this.find(
             { students: student },
             { populate: ['students', 'teachers'] } // Voegt student en teacher objecten toe
         );
     }
 
-    public findByTeacher(teacher: Teacher): Promise<Class[]> {
+    public async findByTeacher(teacher: Teacher): Promise<Class[]> {
         return this.find({ teachers: teacher }, { populate: ['students', 'teachers'] });
     }
 }

backend/src/data/classes/teacher-invitation-repository.ts

@@ -4,16 +4,16 @@ import { TeacherInvitation } from '../../entities/classes/teacher-invitation.ent
 import { Teacher } from '../../entities/users/teacher.entity.js';
 
 export class TeacherInvitationRepository extends DwengoEntityRepository<TeacherInvitation> {
-    public findAllInvitationsForClass(clazz: Class): Promise<TeacherInvitation[]> {
+    public async findAllInvitationsForClass(clazz: Class): Promise<TeacherInvitation[]> {
         return this.findAll({ where: { class: clazz } });
     }
-    public findAllInvitationsBy(sender: Teacher): Promise<TeacherInvitation[]> {
+    public async findAllInvitationsBy(sender: Teacher): Promise<TeacherInvitation[]> {
         return this.findAll({ where: { sender: sender } });
     }
-    public findAllInvitationsFor(receiver: Teacher): Promise<TeacherInvitation[]> {
+    public async findAllInvitationsFor(receiver: Teacher): Promise<TeacherInvitation[]> {
         return this.findAll({ where: { receiver: receiver } });
     }
-    public deleteBy(clazz: Class, sender: Teacher, receiver: Teacher): Promise<void> {
+    public async deleteBy(clazz: Class, sender: Teacher, receiver: Teacher): Promise<void> {
         return this.deleteWhere({
             sender: sender,
             receiver: receiver,

backend/src/data/content/attachment-repository.ts

@@ -1,10 +1,10 @@
 import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { Attachment } from '../../entities/content/attachment.entity.js';
-import { Language } from '../../entities/content/language';
+import { Language } from '@dwengo-1/common/util/language';
 import { LearningObjectIdentifier } from '../../entities/content/learning-object-identifier';
 
 export class AttachmentRepository extends DwengoEntityRepository<Attachment> {
-    public findByLearningObjectIdAndName(learningObjectId: LearningObjectIdentifier, name: string): Promise<Attachment | null> {
+    public async findByLearningObjectIdAndName(learningObjectId: LearningObjectIdentifier, name: string): Promise<Attachment | null> {
         return this.findOne({
             learningObject: {
                 hruid: learningObjectId.hruid,
@@ -15,7 +15,11 @@ export class AttachmentRepository extends DwengoEntityRepository<Attachment> {
         });
     }
 
-    public findByMostRecentVersionOfLearningObjectAndName(hruid: string, language: Language, attachmentName: string): Promise<Attachment | null> {
+    public async findByMostRecentVersionOfLearningObjectAndName(
+        hruid: string,
+        language: Language,
+        attachmentName: string
+    ): Promise<Attachment | null> {
         return this.findOne(
             {
                 learningObject: {

backend/src/data/content/learning-object-repository.ts

@@ -1,11 +1,11 @@
 import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
 import { LearningObjectIdentifier } from '../../entities/content/learning-object-identifier.js';
-import { Language } from '../../entities/content/language.js';
+import { Language } from '@dwengo-1/common/util/language';
 import { Teacher } from '../../entities/users/teacher.entity.js';
 
 export class LearningObjectRepository extends DwengoEntityRepository<LearningObject> {
-    public findByIdentifier(identifier: LearningObjectIdentifier): Promise<LearningObject | null> {
+    public async findByIdentifier(identifier: LearningObjectIdentifier): Promise<LearningObject | null> {
         return this.findOne(
             {
                 hruid: identifier.hruid,
@@ -18,7 +18,7 @@ export class LearningObjectRepository extends DwengoEntityRepository<LearningObj
         );
     }
 
-    public findLatestByHruidAndLanguage(hruid: string, language: Language) {
+    public async findLatestByHruidAndLanguage(hruid: string, language: Language): Promise<LearningObject | null> {
         return this.findOne(
             {
                 hruid: hruid,
@@ -33,7 +33,7 @@ export class LearningObjectRepository extends DwengoEntityRepository<LearningObj
         );
     }
 
-    public findAllByTeacher(teacher: Teacher): Promise<LearningObject[]> {
+    public async findAllByTeacher(teacher: Teacher): Promise<LearningObject[]> {
         return this.find(
             { admins: teacher },
             { populate: ['admins'] } // Make sure to load admin relations

backend/src/data/content/learning-path-repository.ts

@@ -1,9 +1,9 @@
 import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { LearningPath } from '../../entities/content/learning-path.entity.js';
-import { Language } from '../../entities/content/language.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 export class LearningPathRepository extends DwengoEntityRepository<LearningPath> {
-    public findByHruidAndLanguage(hruid: string, language: Language): Promise<LearningPath | null> {
+    public async findByHruidAndLanguage(hruid: string, language: Language): Promise<LearningPath | null> {
         return this.findOne({ hruid: hruid, language: language }, { populate: ['nodes', 'nodes.transitions'] });
     }
 

backend/src/data/dwengo-entity-repository.ts

@@ -1,12 +1,14 @@
 import { EntityRepository, FilterQuery } from '@mikro-orm/core';
+import { EntityAlreadyExistsException } from '../exceptions/entity-already-exists-exception.js';
 
 export abstract class DwengoEntityRepository<T extends object> extends EntityRepository<T> {
-    public async save(entity: T) {
-        const em = this.getEntityManager();
-        em.persist(entity);
-        await em.flush();
+    public async save(entity: T, options?: { preventOverwrite?: boolean }): Promise<void> {
+        if (options?.preventOverwrite && (await this.findOne(entity))) {
+            throw new EntityAlreadyExistsException(`A ${this.getEntityName()} with this identifier already exists.`);
+        }
+        await this.getEntityManager().persistAndFlush(entity);
     }
-    public async deleteWhere(query: FilterQuery<T>) {
+    public async deleteWhere(query: FilterQuery<T>): Promise<void> {
         const toDelete = await this.findOne(query);
         const em = this.getEntityManager();
         if (toDelete) {

backend/src/data/questions/answer-repository.ts

@@ -4,7 +4,7 @@ import { Question } from '../../entities/questions/question.entity.js';
 import { Teacher } from '../../entities/users/teacher.entity.js';
 
 export class AnswerRepository extends DwengoEntityRepository<Answer> {
-    public createAnswer(answer: { toQuestion: Question; author: Teacher; content: string }): Promise<Answer> {
+    public async createAnswer(answer: { toQuestion: Question; author: Teacher; content: string }): Promise<Answer> {
         const answerEntity = this.create({
             toQuestion: answer.toQuestion,
             author: answer.author,
@@ -13,13 +13,13 @@ export class AnswerRepository extends DwengoEntityRepository<Answer> {
         });
         return this.insert(answerEntity);
     }
-    public findAllAnswersToQuestion(question: Question): Promise<Answer[]> {
+    public async findAllAnswersToQuestion(question: Question): Promise<Answer[]> {
         return this.findAll({
             where: { toQuestion: question },
             orderBy: { sequenceNumber: 'ASC' },
         });
     }
-    public removeAnswerByQuestionAndSequenceNumber(question: Question, sequenceNumber: number): Promise<void> {
+    public async removeAnswerByQuestionAndSequenceNumber(question: Question, sequenceNumber: number): Promise<void> {
         return this.deleteWhere({
             toQuestion: question,
             sequenceNumber: sequenceNumber,

backend/src/data/questions/question-repository.ts

@@ -5,7 +5,7 @@ import { Student } from '../../entities/users/student.entity.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
 
 export class QuestionRepository extends DwengoEntityRepository<Question> {
-    public createQuestion(question: { loId: LearningObjectIdentifier; author: Student; content: string }): Promise<Question> {
+    public async createQuestion(question: { loId: LearningObjectIdentifier; author: Student; content: string }): Promise<Question> {
         const questionEntity = this.create({
             learningObjectHruid: question.loId.hruid,
             learningObjectLanguage: question.loId.language,
@@ -21,7 +21,7 @@ export class QuestionRepository extends DwengoEntityRepository<Question> {
         questionEntity.content = question.content;
         return this.insert(questionEntity);
     }
-    public findAllQuestionsAboutLearningObject(loId: LearningObjectIdentifier): Promise<Question[]> {
+    public async findAllQuestionsAboutLearningObject(loId: LearningObjectIdentifier): Promise<Question[]> {
         return this.findAll({
             where: {
                 learningObjectHruid: loId.hruid,
@@ -33,7 +33,7 @@ export class QuestionRepository extends DwengoEntityRepository<Question> {
             },
         });
     }
-    public removeQuestionByLearningObjectAndSequenceNumber(loId: LearningObjectIdentifier, sequenceNumber: number): Promise<void> {
+    public async removeQuestionByLearningObjectAndSequenceNumber(loId: LearningObjectIdentifier, sequenceNumber: number): Promise<void> {
         return this.deleteWhere({
             learningObjectHruid: loId.hruid,
             learningObjectLanguage: loId.language,
@@ -54,4 +54,11 @@ export class QuestionRepository extends DwengoEntityRepository<Question> {
             orderBy: { timestamp: 'ASC' },
         });
     }
+
+    public async findAllByAuthor(author: Student): Promise<Question[]> {
+        return this.findAll({
+            where: { author },
+            orderBy: { timestamp: 'DESC' }, // New to old
+        });
+    }
 }

backend/src/data/repositories.ts

@@ -34,8 +34,8 @@ let entityManager: EntityManager | undefined;
 /**
  * Execute all the database operations within the function f in a single transaction.
  */
-export function transactional<T>(f: () => Promise<T>) {
-    entityManager?.transactional(f);
+export async function transactional<T>(f: () => Promise<T>): Promise<void> {
+    await entityManager?.transactional(f);
 }
 
 function repositoryGetter<T extends AnyEntity, R extends EntityRepository<T>>(entity: EntityName<T>): () => R {

backend/src/data/themes.ts

@@ -1,7 +1,4 @@
-export interface Theme {
-    title: string;
-    hruids: string[];
-}
+import { Theme } from '@dwengo-1/common/interfaces/theme';
 
 export const themes: Theme[] = [
     {

backend/src/data/users/student-repository.ts

@@ -1,14 +1,11 @@
 import { Student } from '../../entities/users/student.entity.js';
 import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
-// Import { UserRepository } from './user-repository.js';
-
-// Export class StudentRepository extends UserRepository<Student> {}
 
 export class StudentRepository extends DwengoEntityRepository<Student> {
-    public findByUsername(username: string): Promise<Student | null> {
+    public async findByUsername(username: string): Promise<Student | null> {
         return this.findOne({ username: username });
     }
-    public deleteByUsername(username: string): Promise<void> {
+    public async deleteByUsername(username: string): Promise<void> {
         return this.deleteWhere({ username: username });
     }
 }

backend/src/data/users/teacher-repository.ts

@@ -2,10 +2,10 @@ import { Teacher } from '../../entities/users/teacher.entity.js';
 import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 
 export class TeacherRepository extends DwengoEntityRepository<Teacher> {
-    public findByUsername(username: string): Promise<Teacher | null> {
+    public async findByUsername(username: string): Promise<Teacher | null> {
         return this.findOne({ username: username });
     }
-    public deleteByUsername(username: string): Promise<void> {
+    public async deleteByUsername(username: string): Promise<void> {
         return this.deleteWhere({ username: username });
     }
 }

backend/src/data/users/user-repository.ts

@@ -2,10 +2,10 @@ import { DwengoEntityRepository } from '../dwengo-entity-repository.js';
 import { User } from '../../entities/users/user.entity.js';
 
 export class UserRepository<T extends User> extends DwengoEntityRepository<T> {
-    public findByUsername(username: string): Promise<T | null> {
+    public async findByUsername(username: string): Promise<T | null> {
         return this.findOne({ username } as Partial<T>);
     }
-    public deleteByUsername(username: string): Promise<void> {
+    public async deleteByUsername(username: string): Promise<void> {
         return this.deleteWhere({ username } as Partial<T>);
     }
 }

backend/src/entities/assignments/assignment.entity.ts

@@ -1,7 +1,7 @@
 import { Entity, Enum, ManyToOne, OneToMany, PrimaryKey, Property } from '@mikro-orm/core';
 import { Class } from '../classes/class.entity.js';
 import { Group } from './group.entity.js';
-import { Language } from '../content/language.js';
+import { Language } from '@dwengo-1/common/util/language';
 import { AssignmentRepository } from '../../data/assignments/assignment-repository.js';
 
 @Entity({

backend/src/entities/assignments/submission.entity.ts

@@ -1,8 +1,8 @@
 import { Student } from '../users/student.entity.js';
 import { Group } from './group.entity.js';
 import { Entity, Enum, ManyToOne, PrimaryKey, Property } from '@mikro-orm/core';
-import { Language } from '../content/language.js';
 import { SubmissionRepository } from '../../data/assignments/submission-repository.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 @Entity({ repository: () => SubmissionRepository })
 export class Submission {
@@ -16,7 +16,7 @@ export class Submission {
     learningObjectLanguage!: Language;
 
     @PrimaryKey({ type: 'numeric' })
-    learningObjectVersion: number = 1;
+    learningObjectVersion = 1;
 
     @PrimaryKey({ type: 'integer', autoincrement: true })
     submissionNumber?: number;

backend/src/entities/classes/class-join-request.entity.ts

@@ -2,12 +2,7 @@ import { Entity, Enum, ManyToOne } from '@mikro-orm/core';
 import { Student } from '../users/student.entity.js';
 import { Class } from './class.entity.js';
 import { ClassJoinRequestRepository } from '../../data/classes/class-join-request-repository.js';
-
-export enum ClassJoinRequestStatus {
-    Open = 'open',
-    Accepted = 'accepted',
-    Declined = 'declined',
-}
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
 
 @Entity({
     repository: () => ClassJoinRequestRepository,

backend/src/entities/content/educational-goal.entity.ts

@@ -0,0 +1,10 @@
+import { Embeddable, Property } from '@mikro-orm/core';
+
+@Embeddable()
+export class EducationalGoal {
+    @Property({ type: 'string' })
+    source!: string;
+
+    @Property({ type: 'string' })
+    id!: string;
+}

backend/src/entities/content/language.ts

@@ -1,193 +0,0 @@
-export enum Language {
-    Afar = 'aa',
-    Abkhazian = 'ab',
-    Afrikaans = 'af',
-    Akan = 'ak',
-    Albanian = 'sq',
-    Amharic = 'am',
-    Arabic = 'ar',
-    Aragonese = 'an',
-    Armenian = 'hy',
-    Assamese = 'as',
-    Avaric = 'av',
-    Avestan = 'ae',
-    Aymara = 'ay',
-    Azerbaijani = 'az',
-    Bashkir = 'ba',
-    Bambara = 'bm',
-    Basque = 'eu',
-    Belarusian = 'be',
-    Bengali = 'bn',
-    Bihari = 'bh',
-    Bislama = 'bi',
-    Bosnian = 'bs',
-    Breton = 'br',
-    Bulgarian = 'bg',
-    Burmese = 'my',
-    Catalan = 'ca',
-    Chamorro = 'ch',
-    Chechen = 'ce',
-    Chinese = 'zh',
-    ChurchSlavic = 'cu',
-    Chuvash = 'cv',
-    Cornish = 'kw',
-    Corsican = 'co',
-    Cree = 'cr',
-    Czech = 'cs',
-    Danish = 'da',
-    Divehi = 'dv',
-    Dutch = 'nl',
-    Dzongkha = 'dz',
-    English = 'en',
-    Esperanto = 'eo',
-    Estonian = 'et',
-    Ewe = 'ee',
-    Faroese = 'fo',
-    Fijian = 'fj',
-    Finnish = 'fi',
-    French = 'fr',
-    Frisian = 'fy',
-    Fulah = 'ff',
-    Georgian = 'ka',
-    German = 'de',
-    Gaelic = 'gd',
-    Irish = 'ga',
-    Galician = 'gl',
-    Manx = 'gv',
-    Greek = 'el',
-    Guarani = 'gn',
-    Gujarati = 'gu',
-    Haitian = 'ht',
-    Hausa = 'ha',
-    Hebrew = 'he',
-    Herero = 'hz',
-    Hindi = 'hi',
-    HiriMotu = 'ho',
-    Croatian = 'hr',
-    Hungarian = 'hu',
-    Igbo = 'ig',
-    Icelandic = 'is',
-    Ido = 'io',
-    SichuanYi = 'ii',
-    Inuktitut = 'iu',
-    Interlingue = 'ie',
-    Interlingua = 'ia',
-    Indonesian = 'id',
-    Inupiaq = 'ik',
-    Italian = 'it',
-    Javanese = 'jv',
-    Japanese = 'ja',
-    Kalaallisut = 'kl',
-    Kannada = 'kn',
-    Kashmiri = 'ks',
-    Kanuri = 'kr',
-    Kazakh = 'kk',
-    Khmer = 'km',
-    Kikuyu = 'ki',
-    Kinyarwanda = 'rw',
-    Kirghiz = 'ky',
-    Komi = 'kv',
-    Kongo = 'kg',
-    Korean = 'ko',
-    Kuanyama = 'kj',
-    Kurdish = 'ku',
-    Lao = 'lo',
-    Latin = 'la',
-    Latvian = 'lv',
-    Limburgan = 'li',
-    Lingala = 'ln',
-    Lithuanian = 'lt',
-    Luxembourgish = 'lb',
-    LubaKatanga = 'lu',
-    Ganda = 'lg',
-    Macedonian = 'mk',
-    Marshallese = 'mh',
-    Malayalam = 'ml',
-    Maori = 'mi',
-    Marathi = 'mr',
-    Malay = 'ms',
-    Malagasy = 'mg',
-    Maltese = 'mt',
-    Mongolian = 'mn',
-    Nauru = 'na',
-    Navajo = 'nv',
-    SouthNdebele = 'nr',
-    NorthNdebele = 'nd',
-    Ndonga = 'ng',
-    Nepali = 'ne',
-    NorwegianNynorsk = 'nn',
-    NorwegianBokmal = 'nb',
-    Norwegian = 'no',
-    Chichewa = 'ny',
-    Occitan = 'oc',
-    Ojibwa = 'oj',
-    Oriya = 'or',
-    Oromo = 'om',
-    Ossetian = 'os',
-    Punjabi = 'pa',
-    Persian = 'fa',
-    Pali = 'pi',
-    Polish = 'pl',
-    Portuguese = 'pt',
-    Pashto = 'ps',
-    Quechua = 'qu',
-    Romansh = 'rm',
-    Romanian = 'ro',
-    Rundi = 'rn',
-    Russian = 'ru',
-    Sango = 'sg',
-    Sanskrit = 'sa',
-    Sinhala = 'si',
-    Slovak = 'sk',
-    Slovenian = 'sl',
-    NorthernSami = 'se',
-    Samoan = 'sm',
-    Shona = 'sn',
-    Sindhi = 'sd',
-    Somali = 'so',
-    Sotho = 'st',
-    Spanish = 'es',
-    Sardinian = 'sc',
-    Serbian = 'sr',
-    Swati = 'ss',
-    Sundanese = 'su',
-    Swahili = 'sw',
-    Swedish = 'sv',
-    Tahitian = 'ty',
-    Tamil = 'ta',
-    Tatar = 'tt',
-    Telugu = 'te',
-    Tajik = 'tg',
-    Tagalog = 'tl',
-    Thai = 'th',
-    Tibetan = 'bo',
-    Tigrinya = 'ti',
-    Tonga = 'to',
-    Tswana = 'tn',
-    Tsonga = 'ts',
-    Turkmen = 'tk',
-    Turkish = 'tr',
-    Twi = 'tw',
-    Uighur = 'ug',
-    Ukrainian = 'uk',
-    Urdu = 'ur',
-    Uzbek = 'uz',
-    Venda = 've',
-    Vietnamese = 'vi',
-    Volapuk = 'vo',
-    Welsh = 'cy',
-    Walloon = 'wa',
-    Wolof = 'wo',
-    Xhosa = 'xh',
-    Yiddish = 'yi',
-    Yoruba = 'yo',
-    Zhuang = 'za',
-    Zulu = 'zu',
-}
-
-export const languageMap: Record<string, Language> = {
-    nl: Language.Dutch,
-    fr: Language.French,
-    en: Language.English,
-    de: Language.German,
-};

backend/src/entities/content/learning-object-identifier.ts

@@ -1,9 +1,11 @@
-import { Language } from './language.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 export class LearningObjectIdentifier {
     constructor(
         public hruid: string,
         public language: Language,
         public version: number
-    ) {}
+    ) {
+        // Do nothing
+    }
 }

backend/src/entities/content/learning-object.entity.ts

@@ -1,28 +1,12 @@
-import { Embeddable, Embedded, Entity, Enum, ManyToMany, OneToMany, PrimaryKey, Property } from '@mikro-orm/core';
-import { Language } from './language.js';
+import { Embedded, Entity, Enum, ManyToMany, OneToMany, PrimaryKey, Property } from '@mikro-orm/core';
 import { Attachment } from './attachment.entity.js';
 import { Teacher } from '../users/teacher.entity.js';
 import { DwengoContentType } from '../../services/learning-objects/processing/content-type.js';
 import { v4 } from 'uuid';
 import { LearningObjectRepository } from '../../data/content/learning-object-repository.js';
-
-@Embeddable()
-export class EducationalGoal {
-    @Property({ type: 'string' })
-    source!: string;
-
-    @Property({ type: 'string' })
-    id!: string;
-}
-
-@Embeddable()
-export class ReturnValue {
-    @Property({ type: 'string' })
-    callbackUrl!: string;
-
-    @Property({ type: 'json' })
-    callbackSchema!: string;
-}
+import { EducationalGoal } from './educational-goal.entity.js';
+import { ReturnValue } from './return-value.entity.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 @Entity({ repository: () => LearningObjectRepository })
 export class LearningObject {
@@ -36,7 +20,7 @@ export class LearningObject {
     language!: Language;
 
     @PrimaryKey({ type: 'number' })
-    version: number = 1;
+    version = 1;
 
     @Property({ type: 'uuid', unique: true })
     uuid = v4();
@@ -62,7 +46,7 @@ export class LearningObject {
     targetAges?: number[] = [];
 
     @Property({ type: 'bool' })
-    teacherExclusive: boolean = false;
+    teacherExclusive = false;
 
     @Property({ type: 'array' })
     skosConcepts: string[] = [];
@@ -74,10 +58,10 @@ export class LearningObject {
     educationalGoals: EducationalGoal[] = [];
 
     @Property({ type: 'string' })
-    copyright: string = '';
+    copyright = '';
 
     @Property({ type: 'string' })
-    license: string = '';
+    license = '';
 
     @Property({ type: 'smallint', nullable: true })
     difficulty?: number;
@@ -91,7 +75,7 @@ export class LearningObject {
     returnValue!: ReturnValue;
 
     @Property({ type: 'bool' })
-    available: boolean = true;
+    available = true;
 
     @Property({ type: 'string', nullable: true })
     contentLocation?: string;

backend/src/entities/content/learning-path-node.entity.ts

@@ -1,7 +1,7 @@
 import { Entity, Enum, ManyToOne, OneToMany, PrimaryKey, Property, Rel } from '@mikro-orm/core';
-import { Language } from './language.js';
 import { LearningPath } from './learning-path.entity.js';
 import { LearningPathTransition } from './learning-path-transition.entity.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 @Entity()
 export class LearningPathNode {

backend/src/entities/content/learning-path.entity.ts

@@ -1,8 +1,8 @@
 import { Entity, Enum, ManyToMany, OneToMany, PrimaryKey, Property } from '@mikro-orm/core';
-import { Language } from './language.js';
 import { Teacher } from '../users/teacher.entity.js';
 import { LearningPathRepository } from '../../data/content/learning-path-repository.js';
 import { LearningPathNode } from './learning-path-node.entity.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 @Entity({ repository: () => LearningPathRepository })
 export class LearningPath {

backend/src/entities/content/return-value.entity.ts

@@ -0,0 +1,10 @@
+import { Embeddable, Property } from '@mikro-orm/core';
+
+@Embeddable()
+export class ReturnValue {
+    @Property({ type: 'string' })
+    callbackUrl!: string;
+
+    @Property({ type: 'json' })
+    callbackSchema!: string;
+}

backend/src/entities/questions/question.entity.ts

@@ -1,7 +1,7 @@
 import { Entity, Enum, ManyToOne, PrimaryKey, Property } from '@mikro-orm/core';
-import { Language } from '../content/language.js';
 import { Student } from '../users/student.entity.js';
 import { QuestionRepository } from '../../data/questions/question-repository.js';
+import { Language } from '@dwengo-1/common/util/language';
 
 @Entity({ repository: () => QuestionRepository })
 export class Question {
@@ -15,7 +15,7 @@ export class Question {
     learningObjectLanguage!: Language;
 
     @PrimaryKey({ type: 'number' })
-    learningObjectVersion: number = 1;
+    learningObjectVersion = 1;
 
     @PrimaryKey({ type: 'integer', autoincrement: true })
     sequenceNumber?: number;

backend/src/entities/users/student.entity.ts

@@ -13,12 +13,4 @@ export class Student extends User {
 
     @ManyToMany(() => Group)
     groups!: Collection<Group>;
-
-    constructor(
-        public username: string,
-        public firstName: string,
-        public lastName: string
-    ) {
-        super();
-    }
 }

backend/src/entities/users/teacher.entity.ts

@@ -7,12 +7,4 @@ import { TeacherRepository } from '../../data/users/teacher-repository.js';
 export class Teacher extends User {
     @ManyToMany(() => Class)
     classes!: Collection<Class>;
-
-    constructor(
-        public username: string,
-        public firstName: string,
-        public lastName: string
-    ) {
-        super();
-    }
 }

backend/src/entities/users/user.entity.ts

@@ -6,8 +6,8 @@ export abstract class User {
     username!: string;
 
     @Property()
-    firstName: string = '';
+    firstName = '';
 
     @Property()
-    lastName: string = '';
+    lastName = '';
 }

backend/src/exceptions.ts

@@ -1,42 +0,0 @@
-/**
- * Exception for HTTP 400 Bad Request
- */
-export class BadRequestException extends Error {
-    public status = 400;
-
-    constructor(error: string) {
-        super(error);
-    }
-}
-
-/**
- * Exception for HTTP 401 Unauthorized
- */
-export class UnauthorizedException extends Error {
-    status = 401;
-    constructor(message: string = 'Unauthorized') {
-        super(message);
-    }
-}
-
-/**
- * Exception for HTTP 403 Forbidden
- */
-export class ForbiddenException extends Error {
-    status = 403;
-
-    constructor(message: string = 'Forbidden') {
-        super(message);
-    }
-}
-
-/**
- * Exception for HTTP 404 Not Found
- */
-export class NotFoundException extends Error {
-    public status = 404;
-
-    constructor(error: string) {
-        super(error);
-    }
-}

backend/src/exceptions/bad-request-exception.ts

@@ -0,0 +1,10 @@
+import { ExceptionWithHttpState } from './exception-with-http-state.js';
+
+/**
+ * Exception for HTTP 400 Bad Request
+ */
+export class BadRequestException extends ExceptionWithHttpState {
+    constructor(error: string) {
+        super(400, error);
+    }
+}

backend/src/exceptions/conflict-exception.ts

@@ -0,0 +1,12 @@
+import { ExceptionWithHttpState } from './exception-with-http-state.js';
+
+/**
+ * Exception for HTTP 409 Conflict
+ */
+export class ConflictException extends ExceptionWithHttpState {
+    public status = 409;
+
+    constructor(error: string) {
+        super(409, error);
+    }
+}

backend/src/exceptions/entity-already-exists-exception.ts

@@ -0,0 +1,7 @@
+import { ConflictException } from './conflict-exception.js';
+
+export class EntityAlreadyExistsException extends ConflictException {
+    constructor(message: string) {
+        super(message);
+    }
+}

backend/src/exceptions/exception-with-http-state.ts

@@ -0,0 +1,11 @@
+/**
+ * Exceptions which are associated with a HTTP error code.
+ */
+export abstract class ExceptionWithHttpState extends Error {
+    constructor(
+        public status: number,
+        public error: string
+    ) {
+        super(error);
+    }
+}

backend/src/exceptions/forbidden-exception.ts

@@ -0,0 +1,12 @@
+import { ExceptionWithHttpState } from './exception-with-http-state.js';
+
+/**
+ * Exception for HTTP 403 Forbidden
+ */
+export class ForbiddenException extends ExceptionWithHttpState {
+    status = 403;
+
+    constructor(message = 'Forbidden') {
+        super(403, message);
+    }
+}

backend/src/exceptions/not-found-exception.ts

@@ -0,0 +1,12 @@
+import { ExceptionWithHttpState } from './exception-with-http-state.js';
+
+/**
+ * Exception for HTTP 404 Not Found
+ */
+export class NotFoundException extends ExceptionWithHttpState {
+    public status = 404;
+
+    constructor(error: string) {
+        super(404, error);
+    }
+}

backend/src/exceptions/unauthorized-exception.ts

@@ -0,0 +1,10 @@
+import { ExceptionWithHttpState } from './exception-with-http-state.js';
+
+/**
+ * Exception for HTTP 401 Unauthorized
+ */
+export class UnauthorizedException extends ExceptionWithHttpState {
+    constructor(message = 'Unauthorized') {
+        super(401, message);
+    }
+}

backend/src/interfaces/answer.ts

@@ -1,14 +1,7 @@
-import { mapToUserDTO, UserDTO } from './user.js';
-import { mapToQuestionDTO, mapToQuestionId, QuestionDTO, QuestionId } from './question.js';
+import { mapToUserDTO } from './user.js';
+import { mapToQuestionDTO, mapToQuestionDTOId } from './question.js';
 import { Answer } from '../entities/questions/answer.entity.js';
-
-export interface AnswerDTO {
-    author: UserDTO;
-    toQuestion: QuestionDTO;
-    sequenceNumber: number;
-    timestamp: string;
-    content: string;
-}
+import { AnswerDTO, AnswerId } from '@dwengo-1/common/interfaces/answer';
 
 /**
  * Convert a Question entity to a DTO format.
@@ -23,16 +16,10 @@ export function mapToAnswerDTO(answer: Answer): AnswerDTO {
     };
 }
 
-export interface AnswerId {
-    author: string;
-    toQuestion: QuestionId;
-    sequenceNumber: number;
-}
-
-export function mapToAnswerId(answer: AnswerDTO): AnswerId {
+export function mapToAnswerDTOId(answer: Answer): AnswerId {
     return {
         author: answer.author.username,
-        toQuestion: mapToQuestionId(answer.toQuestion),
-        sequenceNumber: answer.sequenceNumber,
+        toQuestion: mapToQuestionDTOId(answer.toQuestion),
+        sequenceNumber: answer.sequenceNumber!,
     };
 }

backend/src/interfaces/assignment.ts

@@ -1,18 +1,9 @@
+import { languageMap } from '@dwengo-1/common/util/language';
 import { FALLBACK_LANG } from '../config.js';
 import { Assignment } from '../entities/assignments/assignment.entity.js';
 import { Class } from '../entities/classes/class.entity.js';
-import { languageMap } from '../entities/content/language.js';
-import { GroupDTO } from './group.js';
-
-export interface AssignmentDTO {
-    id: number;
-    class: string; // Id of class 'within'
-    title: string;
-    description: string;
-    learningPath: string;
-    language: string;
-    groups?: GroupDTO[] | string[]; // TODO
-}
+import { getLogger } from '../logging/initalize.js';
+import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
 
 export function mapToAssignmentDTOId(assignment: Assignment): AssignmentDTO {
     return {
@@ -46,5 +37,7 @@ export function mapToAssignment(assignmentData: AssignmentDTO, cls: Class): Assi
     assignment.learningPathLanguage = languageMap[assignmentData.language] || FALLBACK_LANG;
     assignment.within = cls;
 
+    getLogger().debug(assignment);
+
     return assignment;
 }

backend/src/interfaces/class.ts

@@ -2,14 +2,7 @@ import { Collection } from '@mikro-orm/core';
 import { Class } from '../entities/classes/class.entity.js';
 import { Student } from '../entities/users/student.entity.js';
 import { Teacher } from '../entities/users/teacher.entity.js';
-
-export interface ClassDTO {
-    id: string;
-    displayName: string;
-    teachers: string[];
-    students: string[];
-    joinRequests: string[];
-}
+import { ClassDTO } from '@dwengo-1/common/interfaces/class';
 
 export function mapToClassDTO(cls: Class): ClassDTO {
     return {

backend/src/interfaces/group.ts

@@ -1,12 +1,7 @@
 import { Group } from '../entities/assignments/group.entity.js';
-import { AssignmentDTO, mapToAssignmentDTO } from './assignment.js';
-import { mapToStudentDTO, StudentDTO } from './student.js';
-
-export interface GroupDTO {
-    assignment: number | AssignmentDTO;
-    groupNumber: number;
-    members: string[] | StudentDTO[];
-}
+import { mapToAssignmentDTO } from './assignment.js';
+import { mapToStudentDTO } from './student.js';
+import { GroupDTO } from '@dwengo-1/common/interfaces/group';
 
 export function mapToGroupDTO(group: Group): GroupDTO {
     return {

backend/src/interfaces/learning-content.ts

@@ -1,112 +0,0 @@
-import { Language } from '../entities/content/language';
-
-export interface Transition {
-    default: boolean;
-    _id: string;
-    next: {
-        _id: string;
-        hruid: string;
-        version: number;
-        language: string;
-    };
-}
-
-export interface LearningObjectIdentifier {
-    hruid: string;
-    language: Language;
-    version?: number;
-}
-
-export interface LearningObjectNode {
-    _id: string;
-    learningobject_hruid: string;
-    version: number;
-    language: Language;
-    start_node?: boolean;
-    transitions: Transition[];
-    created_at: string;
-    updatedAt: string;
-    done?: boolean; // True if a submission exists for this node by the user for whom the learning path is customized.
-}
-
-export interface LearningPath {
-    _id: string;
-    language: string;
-    hruid: string;
-    title: string;
-    description: string;
-    image?: string; // Image might be missing, so it's optional
-    num_nodes: number;
-    num_nodes_left: number;
-    nodes: LearningObjectNode[];
-    keywords: string;
-    target_ages: number[];
-    min_age: number;
-    max_age: number;
-    __order: number;
-}
-
-export interface LearningPathIdentifier {
-    hruid: string;
-    language: Language;
-}
-
-export interface EducationalGoal {
-    source: string;
-    id: string;
-}
-
-export interface ReturnValue {
-    callback_url: string;
-    callback_schema: Record<string, any>;
-}
-
-export interface LearningObjectMetadata {
-    _id: string;
-    uuid: string;
-    hruid: string;
-    version: number;
-    language: Language;
-    title: string;
-    description: string;
-    difficulty: number;
-    estimated_time: number;
-    available: boolean;
-    teacher_exclusive: boolean;
-    educational_goals: EducationalGoal[];
-    keywords: string[];
-    target_ages: number[];
-    content_type: string; // Markdown, image, etc.
-    content_location?: string;
-    skos_concepts?: string[];
-    return_value?: ReturnValue;
-}
-
-export interface FilteredLearningObject {
-    key: string;
-    _id: string;
-    uuid: string;
-    version: number;
-    title: string;
-    htmlUrl: string;
-    language: Language;
-    difficulty: number;
-    estimatedTime?: number;
-    available: boolean;
-    teacherExclusive: boolean;
-    educationalGoals: EducationalGoal[];
-    keywords: string[];
-    description: string;
-    targetAges: number[];
-    contentType: string;
-    contentLocation?: string;
-    skosConcepts?: string[];
-    returnValue?: ReturnValue;
-}
-
-export interface LearningPathResponse {
-    success: boolean;
-    source: string;
-    data: LearningPath[] | null;
-    message?: string;
-}

backend/src/interfaces/question.ts

@@ -1,24 +1,21 @@
 import { Question } from '../entities/questions/question.entity.js';
-import { LearningObjectIdentifier } from '../entities/content/learning-object-identifier.js';
-import { mapToStudentDTO, StudentDTO } from './student.js';
+import { mapToStudentDTO } from './student.js';
+import { QuestionDTO, QuestionId } from '@dwengo-1/common/interfaces/question';
+import { LearningObjectIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
-export interface QuestionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
-    sequenceNumber?: number;
-    author: StudentDTO;
-    timestamp?: string;
-    content: string;
+function getLearningObjectIdentifier(question: Question): LearningObjectIdentifier {
+    return {
+        hruid: question.learningObjectHruid,
+        language: question.learningObjectLanguage,
+        version: question.learningObjectVersion,
+    };
 }
 
 /**
  * Convert a Question entity to a DTO format.
  */
 export function mapToQuestionDTO(question: Question): QuestionDTO {
-    const learningObjectIdentifier = {
-        hruid: question.learningObjectHruid,
-        language: question.learningObjectLanguage,
-        version: question.learningObjectVersion,
-    };
+    const learningObjectIdentifier = getLearningObjectIdentifier(question);
 
     return {
         learningObjectIdentifier,
@@ -29,14 +26,11 @@ export function mapToQuestionDTO(question: Question): QuestionDTO {
     };
 }
 
-export interface QuestionId {
-    learningObjectIdentifier: LearningObjectIdentifier;
-    sequenceNumber: number;
-}
+export function mapToQuestionDTOId(question: Question): QuestionId {
+    const learningObjectIdentifier = getLearningObjectIdentifier(question);
 
-export function mapToQuestionId(question: QuestionDTO): QuestionId {
     return {
-        learningObjectIdentifier: question.learningObjectIdentifier,
+        learningObjectIdentifier,
         sequenceNumber: question.sequenceNumber!,
     };
 }

backend/src/interfaces/student-request.ts

@@ -0,0 +1,23 @@
+import { mapToStudentDTO } from './student.js';
+import { ClassJoinRequest } from '../entities/classes/class-join-request.entity.js';
+import { getClassJoinRequestRepository } from '../data/repositories.js';
+import { Student } from '../entities/users/student.entity.js';
+import { Class } from '../entities/classes/class.entity.js';
+import { ClassJoinRequestDTO } from '@dwengo-1/common/interfaces/class-join-request';
+import { ClassJoinRequestStatus } from '@dwengo-1/common/util/class-join-request';
+
+export function mapToStudentRequestDTO(request: ClassJoinRequest): ClassJoinRequestDTO {
+    return {
+        requester: mapToStudentDTO(request.requester),
+        class: request.class.classId!,
+        status: request.status,
+    };
+}
+
+export function mapToStudentRequest(student: Student, cls: Class): ClassJoinRequest {
+    return getClassJoinRequestRepository().create({
+        requester: student,
+        class: cls,
+        status: ClassJoinRequestStatus.Open,
+    });
+}

backend/src/interfaces/student.ts

@@ -1,17 +1,6 @@
 import { Student } from '../entities/users/student.entity.js';
-
-export interface StudentDTO {
-    id: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-    endpoints?: {
-        classes: string;
-        questions: string;
-        invitations: string;
-        groups: string;
-    };
-}
+import { getStudentRepository } from '../data/repositories.js';
+import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 
 export function mapToStudentDTO(student: Student): StudentDTO {
     return {
@@ -23,7 +12,9 @@ export function mapToStudentDTO(student: Student): StudentDTO {
 }
 
 export function mapToStudent(studentData: StudentDTO): Student {
-    const student = new Student(studentData.username, studentData.firstName, studentData.lastName);
-
-    return student;
+    return getStudentRepository().create({
+        username: studentData.username,
+        firstName: studentData.firstName,
+        lastName: studentData.lastName,
+    });
 }

backend/src/interfaces/submission.ts

@@ -1,26 +1,7 @@
 import { Submission } from '../entities/assignments/submission.entity.js';
-import { Language } from '../entities/content/language.js';
-import { GroupDTO, mapToGroupDTO } from './group.js';
-import { mapToStudent, mapToStudentDTO, StudentDTO } from './student.js';
-import { LearningObjectIdentifier } from './learning-content.js';
-
-export interface SubmissionDTO {
-    learningObjectIdentifier: LearningObjectIdentifier;
-
-    submissionNumber?: number;
-    submitter: StudentDTO;
-    time?: Date;
-    group?: GroupDTO;
-    content: string;
-}
-
-export interface SubmissionDTOId {
-    learningObjectHruid: string;
-    learningObjectLanguage: Language;
-    learningObjectVersion: number;
-
-    submissionNumber?: number;
-}
+import { mapToGroupDTO } from './group.js';
+import { mapToStudent, mapToStudentDTO } from './student.js';
+import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
 
 export function mapToSubmissionDTO(submission: Submission): SubmissionDTO {
     return {

backend/src/interfaces/teacher-invitation.ts

@@ -1,12 +1,7 @@
 import { TeacherInvitation } from '../entities/classes/teacher-invitation.entity.js';
-import { ClassDTO, mapToClassDTO } from './class.js';
-import { mapToUserDTO, UserDTO } from './user.js';
-
-export interface TeacherInvitationDTO {
-    sender: string | UserDTO;
-    receiver: string | UserDTO;
-    class: string | ClassDTO;
-}
+import { mapToClassDTO } from './class.js';
+import { mapToUserDTO } from './user.js';
+import { TeacherInvitationDTO } from '@dwengo-1/common/interfaces/teacher-invitation';
 
 export function mapToTeacherInvitationDTO(invitation: TeacherInvitation): TeacherInvitationDTO {
     return {

backend/src/interfaces/teacher.ts

@@ -1,17 +1,6 @@
 import { Teacher } from '../entities/users/teacher.entity.js';
-
-export interface TeacherDTO {
-    id: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-    endpoints?: {
-        classes: string;
-        questions: string;
-        invitations: string;
-        groups: string;
-    };
-}
+import { getTeacherRepository } from '../data/repositories.js';
+import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
 
 export function mapToTeacherDTO(teacher: Teacher): TeacherDTO {
     return {
@@ -22,8 +11,10 @@ export function mapToTeacherDTO(teacher: Teacher): TeacherDTO {
     };
 }
 
-export function mapToTeacher(TeacherData: TeacherDTO): Teacher {
-    const teacher = new Teacher(TeacherData.username, TeacherData.firstName, TeacherData.lastName);
-
-    return teacher;
+export function mapToTeacher(teacherData: TeacherDTO): Teacher {
+    return getTeacherRepository().create({
+        username: teacherData.username,
+        firstName: teacherData.firstName,
+        lastName: teacherData.lastName,
+    });
 }

backend/src/interfaces/user.ts

@@ -1,17 +1,5 @@
 import { User } from '../entities/users/user.entity.js';
-
-export interface UserDTO {
-    id?: string;
-    username: string;
-    firstName: string;
-    lastName: string;
-    endpoints?: {
-        self: string;
-        classes: string;
-        questions: string;
-        invitations: string;
-    };
-}
+import { UserDTO } from '@dwengo-1/common/interfaces/user';
 
 export function mapToUserDTO(user: User): UserDTO {
     return {

backend/src/logging/initalize.ts

@@ -1,7 +1,7 @@
 import { createLogger, format, Logger as WinstonLogger, transports } from 'winston';
 import LokiTransport from 'winston-loki';
 import { LokiLabels } from 'loki-logger-ts';
-import { EnvVars, getEnvVar } from '../util/envvars.js';
+import { envVars, getEnvVar } from '../util/envVars.js';
 
 export class Logger extends WinstonLogger {
     constructor() {
@@ -9,7 +9,7 @@ export class Logger extends WinstonLogger {
     }
 }
 
-const Labels: LokiLabels = {
+const lokiLabels: LokiLabels = {
     source: 'Dwengo-Backend',
     service: 'API',
     host: 'localhost',
@@ -22,28 +22,28 @@ function initializeLogger(): Logger {
         return logger;
     }
 
-    const logLevel = getEnvVar(EnvVars.LogLevel);
+    const logLevel = getEnvVar(envVars.LogLevel);
 
     const consoleTransport = new transports.Console({
-        level: getEnvVar(EnvVars.LogLevel),
+        level: getEnvVar(envVars.LogLevel),
         format: format.combine(format.cli(), format.colorize()),
     });
 
-    if (getEnvVar(EnvVars.RunMode) === 'dev') {
+    if (getEnvVar(envVars.RunMode) === 'dev') {
         return createLogger({
             transports: [consoleTransport],
         });
     }
 
-    const lokiHost = getEnvVar(EnvVars.LokiHost);
+    const lokiHost = getEnvVar(envVars.LokiHost);
 
     const lokiTransport: LokiTransport = new LokiTransport({
         host: lokiHost,
-        labels: Labels,
+        labels: lokiLabels,
         level: logLevel,
         json: true,
         format: format.combine(format.timestamp(), format.json()),
-        onConnectionError: (err) => {
+        onConnectionError: (err): void => {
             // eslint-disable-next-line no-console
             console.error(`Connection error: ${err}`);
         },

backend/src/logging/mikroOrmLogger.ts

@@ -5,35 +5,54 @@ import { LokiLabels } from 'loki-logger-ts';
 export class MikroOrmLogger extends DefaultLogger {
     private logger: Logger = getLogger();
 
-    log(namespace: LoggerNamespace, message: string, context?: LogContext) {
+    static createMessage(namespace: LoggerNamespace, messageArg: string, context?: LogContext): unknown {
+        const labels: LokiLabels = {
+            service: 'ORM',
+        };
+
+        let message: string;
+        if (context?.label) {
+            message = `[${namespace}] (${context.label}) ${messageArg}`;
+        } else {
+            message = `[${namespace}] ${messageArg}`;
+        }
+
+        return {
+            message: message,
+            labels: labels,
+            context: context,
+        };
+    }
+
+    log(namespace: LoggerNamespace, message: string, context?: LogContext): void {
         if (!this.isEnabled(namespace, context)) {
             return;
         }
 
         switch (namespace) {
             case 'query':
-                this.logger.debug(this.createMessage(namespace, message, context));
+                this.logger.debug(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             case 'query-params':
                 // TODO Which log level should this be?
-                this.logger.info(this.createMessage(namespace, message, context));
+                this.logger.info(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             case 'schema':
-                this.logger.info(this.createMessage(namespace, message, context));
+                this.logger.info(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             case 'discovery':
-                this.logger.debug(this.createMessage(namespace, message, context));
+                this.logger.debug(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             case 'info':
-                this.logger.info(this.createMessage(namespace, message, context));
+                this.logger.info(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             case 'deprecated':
-                this.logger.warn(this.createMessage(namespace, message, context));
+                this.logger.warn(MikroOrmLogger.createMessage(namespace, message, context));
                 break;
             default:
                 switch (context?.level) {
                     case 'info':
-                        this.logger.info(this.createMessage(namespace, message, context));
+                        this.logger.info(MikroOrmLogger.createMessage(namespace, message, context));
                         break;
                     case 'warning':
                         this.logger.warn(message);
@@ -47,23 +66,4 @@ export class MikroOrmLogger extends DefaultLogger {
                 }
         }
     }
-
-    private createMessage(namespace: LoggerNamespace, messageArg: string, context?: LogContext) {
-        const labels: LokiLabels = {
-            service: 'ORM',
-        };
-
-        let message: string;
-        if (context?.label) {
-            message = `[${namespace}] (${context?.label}) ${messageArg}`;
-        } else {
-            message = `[${namespace}] ${messageArg}`;
-        }
-
-        return {
-            message: message,
-            labels: labels,
-            context: context,
-        };
-    }
 }

backend/src/logging/responseTimeLogger.ts

@@ -1,7 +1,7 @@
 import { getLogger, Logger } from './initalize.js';
 import { Request, Response } from 'express';
 
-export function responseTimeLogger(req: Request, res: Response, time: number) {
+export function responseTimeLogger(req: Request, res: Response, time: number): void {
     const logger: Logger = getLogger();
 
     const method = req.method;

backend/src/middleware/auth/auth.ts

@@ -1,12 +1,13 @@
-import { EnvVars, getEnvVar } from '../../util/envvars.js';
+import { envVars, getEnvVar } from '../../util/envVars.js';
 import { expressjwt } from 'express-jwt';
+import * as jwt from 'jsonwebtoken';
 import { JwtPayload } from 'jsonwebtoken';
 import jwksClient from 'jwks-rsa';
 import * as express from 'express';
-import * as jwt from 'jsonwebtoken';
 import { AuthenticatedRequest } from './authenticated-request.js';
 import { AuthenticationInfo } from './authentication-info.js';
-import { ForbiddenException, UnauthorizedException } from '../../exceptions.js';
+import { UnauthorizedException } from '../../exceptions/unauthorized-exception.js';
+import { ForbiddenException } from '../../exceptions/forbidden-exception.js';
 
 const JWKS_CACHE = true;
 const JWKS_RATE_LIMIT = true;
@@ -32,12 +33,12 @@ function createJwksClient(uri: string): jwksClient.JwksClient {
 
 const idpConfigs = {
     student: {
-        issuer: getEnvVar(EnvVars.IdpStudentUrl),
-        jwksClient: createJwksClient(getEnvVar(EnvVars.IdpStudentJwksEndpoint)),
+        issuer: getEnvVar(envVars.IdpStudentUrl),
+        jwksClient: createJwksClient(getEnvVar(envVars.IdpStudentJwksEndpoint)),
     },
     teacher: {
-        issuer: getEnvVar(EnvVars.IdpTeacherUrl),
-        jwksClient: createJwksClient(getEnvVar(EnvVars.IdpTeacherJwksEndpoint)),
+        issuer: getEnvVar(envVars.IdpTeacherUrl),
+        jwksClient: createJwksClient(getEnvVar(envVars.IdpTeacherJwksEndpoint)),
     },
 };
 
@@ -63,7 +64,7 @@ const verifyJwtToken = expressjwt({
         }
         return signingKey.getPublicKey();
     },
-    audience: getEnvVar(EnvVars.IdpAudience),
+    audience: getEnvVar(envVars.IdpAudience),
     algorithms: [JWT_ALGORITHM],
     credentialsRequired: false,
     requestProperty: REQUEST_PROPERTY_FOR_JWT_PAYLOAD,
@@ -74,7 +75,7 @@ const verifyJwtToken = expressjwt({
  */
 function getAuthenticationInfo(req: AuthenticatedRequest): AuthenticationInfo | undefined {
     if (!req.jwtPayload) {
-        return;
+        return undefined;
     }
     const issuer = req.jwtPayload.iss;
     let accountType: 'student' | 'teacher';
@@ -84,8 +85,9 @@ function getAuthenticationInfo(req: AuthenticatedRequest): AuthenticationInfo |
     } else if (issuer === idpConfigs.teacher.issuer) {
         accountType = 'teacher';
     } else {
-        return;
+        return undefined;
     }
+
     return {
         accountType: accountType,
         username: req.jwtPayload[JWT_PROPERTY_NAMES.username]!,
@@ -100,10 +102,10 @@ function getAuthenticationInfo(req: AuthenticatedRequest): AuthenticationInfo |
  * Add the AuthenticationInfo object with the information about the current authentication to the request in order
  * to avoid that the routers have to deal with the JWT token.
  */
-const addAuthenticationInfo = (req: AuthenticatedRequest, res: express.Response, next: express.NextFunction) => {
+function addAuthenticationInfo(req: AuthenticatedRequest, _res: express.Response, next: express.NextFunction): void {
     req.auth = getAuthenticationInfo(req);
     next();
-};
+}
 
 export const authenticateUser = [verifyJwtToken, addAuthenticationInfo];
 
@@ -113,9 +115,8 @@ export const authenticateUser = [verifyJwtToken, addAuthenticationInfo];
  * @param accessCondition Predicate over the current AuthenticationInfo. Access is only granted when this evaluates
  *                        to true.
  */
-export const authorize =
-    (accessCondition: (auth: AuthenticationInfo) => boolean) =>
-    (req: AuthenticatedRequest, res: express.Response, next: express.NextFunction): void => {
+export function authorize(accessCondition: (auth: AuthenticationInfo) => boolean) {
+    return (req: AuthenticatedRequest, _res: express.Response, next: express.NextFunction): void => {
         if (!req.auth) {
             throw new UnauthorizedException();
         } else if (!accessCondition(req.auth)) {
@@ -124,6 +125,7 @@ export const authorize =
             next();
         }
     };
+}
 
 /**
  * Middleware which rejects all unauthenticated users, but accepts all authenticated users.

backend/src/middleware/auth/authentication-info.d.ts

@@ -1,11 +1,11 @@
 /**
  * Object with information about the user who is currently logged in.
  */
-export type AuthenticationInfo = {
+export interface AuthenticationInfo {
     accountType: 'student' | 'teacher';
     username: string;
     name?: string;
     firstName?: string;
     lastName?: string;
     email?: string;
-};
+}

backend/src/middleware/cors.ts

@@ -1,7 +1,7 @@
 import cors from 'cors';
-import { EnvVars, getEnvVar } from '../util/envvars.js';
+import { envVars, getEnvVar } from '../util/envVars.js';
 
 export default cors({
-    origin: getEnvVar(EnvVars.CorsAllowedOrigins).split(','),
-    allowedHeaders: getEnvVar(EnvVars.CorsAllowedHeaders).split(','),
+    origin: getEnvVar(envVars.CorsAllowedOrigins).split(','),
+    allowedHeaders: getEnvVar(envVars.CorsAllowedHeaders).split(','),
 });

backend/src/middleware/error-handling/error-handler.ts

@@ -0,0 +1,15 @@
+import { NextFunction, Request, Response } from 'express';
+import { getLogger, Logger } from '../../logging/initalize.js';
+import { ExceptionWithHttpState } from '../../exceptions/exception-with-http-state.js';
+
+const logger: Logger = getLogger();
+
+export function errorHandler(err: unknown, _req: Request, res: Response, _: NextFunction): void {
+    if (err instanceof ExceptionWithHttpState) {
+        logger.warn(`An error occurred while handling a request: ${err} (-> HTTP ${err.status})`);
+        res.status(err.status).json(err);
+    } else {
+        logger.error(`Unexpected error occurred while handing a request: ${JSON.stringify(err)}`);
+        res.status(500).json(err);
+    }
+}

backend/src/mikro-orm.config.ts

@@ -1,6 +1,6 @@
 import { LoggerOptions, Options } from '@mikro-orm/core';
 import { PostgreSqlDriver } from '@mikro-orm/postgresql';
-import { EnvVars, getEnvVar, getNumericEnvVar } from './util/envvars.js';
+import { envVars, getEnvVar, getNumericEnvVar } from './util/envVars.js';
 import { SqliteDriver } from '@mikro-orm/sqlite';
 import { MikroOrmLogger } from './logging/mikroOrmLogger.js';
 
@@ -42,33 +42,35 @@ const entities = [
     Question,
 ];
 
-function config(testingMode: boolean = false): Options {
+function config(testingMode = false): Options {
     if (testingMode) {
         return {
             driver: SqliteDriver,
-            dbName: getEnvVar(EnvVars.DbName),
+            dbName: getEnvVar(envVars.DbName),
             subscribers: [new SqliteAutoincrementSubscriber()],
             entities: entities,
+            persistOnCreate: false, // Do not implicitly save entities when they are created via `create`.
             // EntitiesTs: entitiesTs,
 
             // Workaround: vitest: `TypeError: Unknown file extension ".ts"` (ERR_UNKNOWN_FILE_EXTENSION)
             // (see https://mikro-orm.io/docs/guide/project-setup#testing-the-endpoint)
-            dynamicImportProvider: (id) => import(id),
+            dynamicImportProvider: async (id) => import(id),
         };
     }
 
     return {
         driver: PostgreSqlDriver,
-        host: getEnvVar(EnvVars.DbHost),
-        port: getNumericEnvVar(EnvVars.DbPort),
-        dbName: getEnvVar(EnvVars.DbName),
-        user: getEnvVar(EnvVars.DbUsername),
-        password: getEnvVar(EnvVars.DbPassword),
+        host: getEnvVar(envVars.DbHost),
+        port: getNumericEnvVar(envVars.DbPort),
+        dbName: getEnvVar(envVars.DbName),
+        user: getEnvVar(envVars.DbUsername),
+        password: getEnvVar(envVars.DbPassword),
         entities: entities,
+        persistOnCreate: false, // Do not implicitly save entities when they are created via `create`.
         // EntitiesTs: entitiesTs,
 
         // Logging
-        debug: getEnvVar(EnvVars.LogLevel) === 'debug',
+        debug: getEnvVar(envVars.LogLevel) === 'debug',
         loggerFactory: (options: LoggerOptions) => new MikroOrmLogger(options),
     };
 }

backend/src/orm.ts

@@ -1,10 +1,10 @@
 import { EntityManager, MikroORM } from '@mikro-orm/core';
 import config from './mikro-orm.config.js';
-import { EnvVars, getEnvVar } from './util/envvars.js';
+import { envVars, getEnvVar } from './util/envVars.js';
 import { getLogger, Logger } from './logging/initalize.js';
 
 let orm: MikroORM | undefined;
-export async function initORM(testingMode: boolean = false) {
+export async function initORM(testingMode = false): Promise<void> {
     const logger: Logger = getLogger();
 
     logger.info('Initializing ORM');
@@ -12,7 +12,7 @@ export async function initORM(testingMode: boolean = false) {
 
     orm = await MikroORM.init(config(testingMode));
     // Update the database scheme if necessary and enabled.
-    if (getEnvVar(EnvVars.DbUpdate)) {
+    if (getEnvVar(envVars.DbUpdate)) {
         await orm.schema.updateSchema();
     } else {
         const diff = await orm.schema.getUpdateSchemaSQL();

backend/src/routes/assignments.ts

@@ -19,7 +19,7 @@ router.get('/:id', getAssignmentHandler);
 
 router.get('/:id/submissions', getAssignmentsSubmissionsHandler);
 
-router.get('/:id/questions', (req, res) => {
+router.get('/:id/questions', (_req, res) => {
     res.json({
         questions: ['0'],
     });

backend/src/routes/auth.ts

@@ -4,21 +4,21 @@ import { authenticatedOnly, studentsOnly, teachersOnly } from '../middleware/aut
 const router = express.Router();
 
 // Returns auth configuration for frontend
-router.get('/config', (req, res) => {
+router.get('/config', (_req, res) => {
     res.json(getFrontendAuthConfig());
 });
 
-router.get('/testAuthenticatedOnly', authenticatedOnly, (req, res) => {
+router.get('/testAuthenticatedOnly', authenticatedOnly, (_req, res) => {
     /* #swagger.security = [{ "student": [ ] }, { "teacher": [ ] }] */
     res.json({ message: 'If you see this, you should be authenticated!' });
 });
 
-router.get('/testStudentsOnly', studentsOnly, (req, res) => {
+router.get('/testStudentsOnly', studentsOnly, (_req, res) => {
     /* #swagger.security = [{ "student": [ ] }] */
     res.json({ message: 'If you see this, you should be a student!' });
 });
 
-router.get('/testTeachersOnly', teachersOnly, (req, res) => {
+router.get('/testTeachersOnly', teachersOnly, (_req, res) => {
     /* #swagger.security = [{ "teacher": [ ] }] */
     res.json({ message: 'If you see this, you should be a teacher!' });
 });

backend/src/routes/groups.ts

@@ -14,7 +14,7 @@ router.get('/:groupid', getGroupHandler);
 router.get('/:groupid/submissions', getGroupSubmissionsHandler);
 
 // The list of questions a group has made
-router.get('/:id/questions', (req, res) => {
+router.get('/:id/questions', (_req, res) => {
     res.json({
         questions: ['0'],
     });

backend/src/routes/student-join-requests.ts

@@ -0,0 +1,19 @@
+import express from 'express';
+import {
+    createStudentRequestHandler,
+    deleteClassJoinRequestHandler,
+    getStudentRequestHandler,
+    getStudentRequestsHandler,
+} from '../controllers/students.js';
+
+const router = express.Router({ mergeParams: true });
+
+router.get('/', getStudentRequestsHandler);
+
+router.post('/', createStudentRequestHandler);
+
+router.get('/:classId', getStudentRequestHandler);
+
+router.delete('/:classId', deleteClassJoinRequestHandler);
+
+export default router;

backend/src/routes/students.ts

@@ -7,8 +7,11 @@ import {
     getStudentClassesHandler,
     getStudentGroupsHandler,
     getStudentHandler,
+    getStudentQuestionsHandler,
     getStudentSubmissionsHandler,
 } from '../controllers/students.js';
+import joinRequestRouter from './student-join-requests.js';
+
 const router = express.Router();
 
 // Root endpoint used to search objects
@@ -16,30 +19,26 @@ router.get('/', getAllStudentsHandler);
 
 router.post('/', createStudentHandler);
 
-router.delete('/', deleteStudentHandler);
-
 router.delete('/:username', deleteStudentHandler);
 
 // Information about a student's profile
 router.get('/:username', getStudentHandler);
 
 // The list of classes a student is in
-router.get('/:id/classes', getStudentClassesHandler);
+router.get('/:username/classes', getStudentClassesHandler);
 
 // The list of submissions a student has made
-router.get('/:id/submissions', getStudentSubmissionsHandler);
+router.get('/:username/submissions', getStudentSubmissionsHandler);
 
 // The list of assignments a student has
-router.get('/:id/assignments', getStudentAssignmentsHandler);
+router.get('/:username/assignments', getStudentAssignmentsHandler);
 
 // The list of groups a student is in
-router.get('/:id/groups', getStudentGroupsHandler);
+router.get('/:username/groups', getStudentGroupsHandler);
 
 // A list of questions a user has created
-router.get('/:id/questions', (req, res) => {
-    res.json({
-        questions: ['0'],
-    });
-});
+router.get('/:username/questions', getStudentQuestionsHandler);
+
+router.use('/:username/joinRequests', joinRequestRouter);
 
 export default router;

backend/src/routes/submissions.ts

@@ -3,7 +3,7 @@ import { createSubmissionHandler, deleteSubmissionHandler, getSubmissionHandler
 const router = express.Router({ mergeParams: true });
 
 // Root endpoint used to search objects
-router.get('/', (req, res) => {
+router.get('/', (_req, res) => {
     res.json({
         submissions: ['0', '1'],
     });

backend/src/routes/teachers.ts

@@ -3,10 +3,12 @@ import {
     createTeacherHandler,
     deleteTeacherHandler,
     getAllTeachersHandler,
+    getStudentJoinRequestHandler,
     getTeacherClassHandler,
     getTeacherHandler,
     getTeacherQuestionHandler,
     getTeacherStudentHandler,
+    updateStudentJoinRequestHandler,
 } from '../controllers/teachers.js';
 const router = express.Router();
 
@@ -15,8 +17,6 @@ router.get('/', getAllTeachersHandler);
 
 router.post('/', createTeacherHandler);
 
-router.delete('/', deleteTeacherHandler);
-
 router.get('/:username', getTeacherHandler);
 
 router.delete('/:username', deleteTeacherHandler);
@@ -27,8 +27,12 @@ router.get('/:username/students', getTeacherStudentHandler);
 
 router.get('/:username/questions', getTeacherQuestionHandler);
 
+router.get('/:username/joinRequests/:classId', getStudentJoinRequestHandler);
+
+router.put('/:username/joinRequests/:classId/:studentUsername', updateStudentJoinRequestHandler);
+
 // Invitations to other classes a teacher received
-router.get('/:id/invitations', (req, res) => {
+router.get('/:id/invitations', (_req, res) => {
     res.json({
         invitations: ['0'],
     });

backend/src/services/assignments.ts

@@ -1,6 +1,9 @@
 import { getAssignmentRepository, getClassRepository, getGroupRepository, getSubmissionRepository } from '../data/repositories.js';
-import { AssignmentDTO, mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
-import { mapToSubmissionDTO, mapToSubmissionDTOId, SubmissionDTO, SubmissionDTOId } from '../interfaces/submission.js';
+import { mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../interfaces/assignment.js';
+import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
+import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
+import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
+import { getLogger } from '../logging/initalize.js';
 
 export async function getAllAssignments(classid: string, full: boolean): Promise<AssignmentDTO[]> {
     const classRepository = getClassRepository();
@@ -37,7 +40,7 @@ export async function createAssignment(classid: string, assignmentData: Assignme
 
         return mapToAssignmentDTO(newAssignment);
     } catch (e) {
-        console.error(e);
+        getLogger().error(e);
         return null;
     }
 }
@@ -83,7 +86,7 @@ export async function getAssignmentsSubmissions(
     const groups = await groupRepository.findAllGroupsForAssignment(assignment);
 
     const submissionRepository = getSubmissionRepository();
-    const submissions = (await Promise.all(groups.map((group) => submissionRepository.findAllSubmissionsForGroup(group)))).flat();
+    const submissions = (await Promise.all(groups.map(async (group) => submissionRepository.findAllSubmissionsForGroup(group)))).flat();
 
     if (full) {
         return submissions.map(mapToSubmissionDTO);

backend/src/services/classes.ts

@@ -1,11 +1,27 @@
 import { getClassRepository, getStudentRepository, getTeacherInvitationRepository, getTeacherRepository } from '../data/repositories.js';
-import { ClassDTO, mapToClassDTO } from '../interfaces/class.js';
-import { mapToStudentDTO, StudentDTO } from '../interfaces/student.js';
-import { mapToTeacherInvitationDTO, mapToTeacherInvitationDTOIds, TeacherInvitationDTO } from '../interfaces/teacher-invitation.js';
+import { mapToClassDTO } from '../interfaces/class.js';
+import { mapToStudentDTO } from '../interfaces/student.js';
+import { mapToTeacherInvitationDTO, mapToTeacherInvitationDTOIds } from '../interfaces/teacher-invitation.js';
 import { getLogger } from '../logging/initalize.js';
+import { NotFoundException } from '../exceptions/not-found-exception.js';
+import { Class } from '../entities/classes/class.entity.js';
+import { ClassDTO } from '@dwengo-1/common/interfaces/class';
+import { TeacherInvitationDTO } from '@dwengo-1/common/interfaces/teacher-invitation';
+import { StudentDTO } from '@dwengo-1/common/interfaces/student';
 
 const logger = getLogger();
 
+export async function fetchClass(classId: string): Promise<Class> {
+    const classRepository = getClassRepository();
+    const cls = await classRepository.findById(classId);
+
+    if (!cls) {
+        throw new NotFoundException('Class with id not found');
+    }
+
+    return cls;
+}
+
 export async function getAllClasses(full: boolean): Promise<ClassDTO[] | string[]> {
     const classRepository = getClassRepository();
     const classes = await classRepository.find({}, { populate: ['students', 'teachers'] });
@@ -23,11 +39,15 @@ export async function getAllClasses(full: boolean): Promise<ClassDTO[] | string[
 export async function createClass(classData: ClassDTO): Promise<ClassDTO | null> {
     const teacherRepository = getTeacherRepository();
     const teacherUsernames = classData.teachers || [];
-    const teachers = (await Promise.all(teacherUsernames.map((id) => teacherRepository.findByUsername(id)))).filter((teacher) => teacher !== null);
+    const teachers = (await Promise.all(teacherUsernames.map(async (id) => teacherRepository.findByUsername(id)))).filter(
+        (teacher) => teacher !== null
+    );
 
     const studentRepository = getStudentRepository();
     const studentUsernames = classData.students || [];
-    const students = (await Promise.all(studentUsernames.map((id) => studentRepository.findByUsername(id)))).filter((student) => student !== null);
+    const students = (await Promise.all(studentUsernames.map(async (id) => studentRepository.findByUsername(id)))).filter(
+        (student) => student !== null
+    );
 
     const classRepository = getClassRepository();
 

backend/src/services/groups.ts

@@ -6,8 +6,11 @@ import {
     getSubmissionRepository,
 } from '../data/repositories.js';
 import { Group } from '../entities/assignments/group.entity.js';
-import { GroupDTO, mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
-import { mapToSubmissionDTO, mapToSubmissionDTOId, SubmissionDTO, SubmissionDTOId } from '../interfaces/submission.js';
+import { mapToGroupDTO, mapToGroupDTOId } from '../interfaces/group.js';
+import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
+import { GroupDTO } from '@dwengo-1/common/interfaces/group';
+import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
+import { getLogger } from '../logging/initalize.js';
 
 export async function getGroup(classId: string, assignmentNumber: number, groupNumber: number, full: boolean): Promise<GroupDTO | null> {
     const classRepository = getClassRepository();
@@ -42,9 +45,11 @@ export async function createGroup(groupData: GroupDTO, classid: string, assignme
     const studentRepository = getStudentRepository();
 
     const memberUsernames = (groupData.members as string[]) || []; // TODO check if groupdata.members is a list
-    const members = (await Promise.all([...memberUsernames].map((id) => studentRepository.findByUsername(id)))).filter((student) => student !== null);
+    const members = (await Promise.all([...memberUsernames].map(async (id) => studentRepository.findByUsername(id)))).filter(
+        (student) => student !== null
+    );
 
-    console.log(members);
+    getLogger().debug(members);
 
     const classRepository = getClassRepository();
     const cls = await classRepository.findById(classid);
@@ -70,7 +75,7 @@ export async function createGroup(groupData: GroupDTO, classid: string, assignme
 
         return newGroup;
     } catch (e) {
-        console.log(e);
+        getLogger().error(e);
         return null;
     }
 }
@@ -94,8 +99,7 @@ export async function getAllGroups(classId: string, assignmentNumber: number, fu
     const groups = await groupRepository.findAllGroupsForAssignment(assignment);
 
     if (full) {
-        console.log('full');
-        console.log(groups);
+        getLogger().debug({ full: full, groups: groups });
         return groups.map(mapToGroupDTO);
     }
 

backend/src/services/learning-objects.ts

@@ -1,6 +1,13 @@
 import { DWENGO_API_BASE } from '../config.js';
 import { fetchWithLogging } from '../util/api-helper.js';
-import { FilteredLearningObject, LearningObjectMetadata, LearningObjectNode, LearningPathResponse } from '../interfaces/learning-content.js';
+
+import {
+    FilteredLearningObject,
+    LearningObjectMetadata,
+    LearningObjectNode,
+    LearningPathResponse,
+} from '@dwengo-1/common/interfaces/learning-content';
+import { getLogger } from '../logging/initalize.js';
 
 function filterData(data: LearningObjectMetadata, htmlUrl: string): FilteredLearningObject {
     return {
@@ -37,7 +44,7 @@ export async function getLearningObjectById(hruid: string, language: string): Pr
     );
 
     if (!metadata) {
-        console.error(`⚠️ WARNING: Learning object "${hruid}" not found.`);
+        getLogger().error(`⚠️ WARNING: Learning object "${hruid}" not found.`);
         return null;
     }
 
@@ -48,7 +55,7 @@ export async function getLearningObjectById(hruid: string, language: string): Pr
 /**
  * Generic function to fetch learning paths
  */
-function fetchLearningPaths(arg0: string[], language: string, arg2: string): LearningPathResponse | PromiseLike<LearningPathResponse> {
+function fetchLearningPaths(_arg0: string[], _language: string, _arg2: string): LearningPathResponse | PromiseLike<LearningPathResponse> {
     throw new Error('Function not implemented.');
 }
 
@@ -60,7 +67,7 @@ async function fetchLearningObjects(hruid: string, full: boolean, language: stri
         const learningPathResponse: LearningPathResponse = await fetchLearningPaths([hruid], language, `Learning path for HRUID "${hruid}"`);
 
         if (!learningPathResponse.success || !learningPathResponse.data?.length) {
-            console.error(`⚠️ WARNING: Learning path "${hruid}" exists but contains no learning objects.`);
+            getLogger().error(`⚠️ WARNING: Learning path "${hruid}" exists but contains no learning objects.`);
             return [];
         }
 
@@ -74,7 +81,7 @@ async function fetchLearningObjects(hruid: string, full: boolean, language: stri
             objects.filter((obj): obj is FilteredLearningObject => obj !== null)
         );
     } catch (error) {
-        console.error('❌ Error fetching learning objects:', error);
+        getLogger().error('❌ Error fetching learning objects:', error);
         return [];
     }
 }

backend/src/services/learning-objects/attachment-service.ts

@@ -1,9 +1,10 @@
 import { getAttachmentRepository } from '../../data/repositories.js';
 import { Attachment } from '../../entities/content/attachment.entity.js';
-import { LearningObjectIdentifier } from '../../interfaces/learning-content.js';
+
+import { LearningObjectIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
 const attachmentService = {
-    getAttachment(learningObjectId: LearningObjectIdentifier, attachmentName: string): Promise<Attachment | null> {
+    async getAttachment(learningObjectId: LearningObjectIdentifier, attachmentName: string): Promise<Attachment | null> {
         const attachmentRepo = getAttachmentRepository();
 
         if (learningObjectId.version) {

backend/src/services/learning-objects/database-learning-object-provider.ts

@@ -1,13 +1,12 @@
 import { LearningObjectProvider } from './learning-object-provider.js';
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
 import { getLearningObjectRepository, getLearningPathRepository } from '../../data/repositories.js';
-import { Language } from '../../entities/content/language.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
 import { getUrlStringForLearningObject } from '../../util/links.js';
 import processingService from './processing/processing-service.js';
 import { NotFoundError } from '@mikro-orm/core';
 import learningObjectService from './learning-object-service.js';
 import { getLogger, Logger } from '../../logging/initalize.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
 const logger: Logger = getLogger();
 
@@ -41,10 +40,10 @@ function convertLearningObject(learningObject: LearningObject | null): FilteredL
     };
 }
 
-function findLearningObjectEntityById(id: LearningObjectIdentifier): Promise<LearningObject | null> {
+async function findLearningObjectEntityById(id: LearningObjectIdentifier): Promise<LearningObject | null> {
     const learningObjectRepo = getLearningObjectRepository();
 
-    return learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language as Language);
+    return learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language);
 }
 
 /**
@@ -65,11 +64,11 @@ const databaseLearningObjectProvider: LearningObjectProvider = {
     async getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
         const learningObjectRepo = getLearningObjectRepository();
 
-        const learningObject = await learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language as Language);
+        const learningObject = await learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language);
         if (!learningObject) {
             return null;
         }
-        return await processingService.render(learningObject, (id) => findLearningObjectEntityById(id));
+        return await processingService.render(learningObject, async (id) => findLearningObjectEntityById(id));
     },
 
     /**
@@ -96,7 +95,7 @@ const databaseLearningObjectProvider: LearningObjectProvider = {
             throw new NotFoundError('The learning path with the given ID could not be found.');
         }
         const learningObjects = await Promise.all(
-            learningPath.nodes.map((it) => {
+            learningPath.nodes.map(async (it) => {
                 const learningObject = learningObjectService.getLearningObjectById({
                     hruid: it.learningObjectHruid,
                     language: it.language,

backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts

@@ -1,5 +1,8 @@
 import { DWENGO_API_BASE } from '../../config.js';
 import { fetchWithLogging } from '../../util/api-helper.js';
+import dwengoApiLearningPathProvider from '../learning-paths/dwengo-api-learning-path-provider.js';
+import { LearningObjectProvider } from './learning-object-provider.js';
+import { getLogger, Logger } from '../../logging/initalize.js';
 import {
     FilteredLearningObject,
     LearningObjectIdentifier,
@@ -7,10 +10,7 @@ import {
     LearningObjectNode,
     LearningPathIdentifier,
     LearningPathResponse,
-} from '../../interfaces/learning-content.js';
-import dwengoApiLearningPathProvider from '../learning-paths/dwengo-api-learning-path-provider.js';
-import { LearningObjectProvider } from './learning-object-provider.js';
-import { getLogger, Logger } from '../../logging/initalize.js';
+} from '@dwengo-1/common/interfaces/learning-content';
 
 const logger: Logger = getLogger();
 
@@ -66,12 +66,13 @@ async function fetchLearningObjects(learningPathId: LearningPathIdentifier, full
         }
 
         const objects = await Promise.all(
-            nodes.map(async (node) =>
-                dwengoApiLearningObjectProvider.getLearningObjectById({
+            nodes.map(async (node) => {
+                const learningObjectId: LearningObjectIdentifier = {
                     hruid: node.learningobject_hruid,
                     language: learningPathId.language,
-                })
-            )
+                };
+                return dwengoApiLearningObjectProvider.getLearningObjectById(learningObjectId);
+            })
         );
         return objects.filter((obj): obj is FilteredLearningObject => obj !== null);
     } catch (error) {
@@ -90,7 +91,7 @@ const dwengoApiLearningObjectProvider: LearningObjectProvider = {
             metadataUrl,
             `Metadata for Learning Object HRUID "${id.hruid}" (language ${id.language})`,
             {
-                params: id,
+                params: { ...id },
             }
         );
 
@@ -123,7 +124,7 @@ const dwengoApiLearningObjectProvider: LearningObjectProvider = {
     async getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
         const htmlUrl = `${DWENGO_API_BASE}/learningObject/getRaw`;
         const html = await fetchWithLogging<string>(htmlUrl, `Metadata for Learning Object HRUID "${id.hruid}" (language ${id.language})`, {
-            params: id,
+            params: { ...id },
         });
 
         if (!html) {

backend/src/services/learning-objects/learning-object-provider.ts

@@ -1,4 +1,4 @@
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
 export interface LearningObjectProvider {
     /**

backend/src/services/learning-objects/learning-object-service.ts

@@ -1,11 +1,11 @@
-import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
 import dwengoApiLearningObjectProvider from './dwengo-api-learning-object-provider.js';
 import { LearningObjectProvider } from './learning-object-provider.js';
-import { EnvVars, getEnvVar } from '../../util/envvars.js';
+import { envVars, getEnvVar } from '../../util/envVars.js';
 import databaseLearningObjectProvider from './database-learning-object-provider.js';
+import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '@dwengo-1/common/interfaces/learning-content';
 
 function getProvider(id: LearningObjectIdentifier): LearningObjectProvider {
-    if (id.hruid.startsWith(getEnvVar(EnvVars.UserContentPrefix))) {
+    if (id.hruid.startsWith(getEnvVar(envVars.UserContentPrefix))) {
         return databaseLearningObjectProvider;
     }
     return dwengoApiLearningObjectProvider;
@@ -18,28 +18,28 @@ const learningObjectService = {
     /**
      * Fetches a single learning object by its HRUID
      */
-    getLearningObjectById(id: LearningObjectIdentifier): Promise<FilteredLearningObject | null> {
+    async getLearningObjectById(id: LearningObjectIdentifier): Promise<FilteredLearningObject | null> {
         return getProvider(id).getLearningObjectById(id);
     },
 
     /**
      * Fetch full learning object data (metadata)
      */
-    getLearningObjectsFromPath(id: LearningPathIdentifier): Promise<FilteredLearningObject[]> {
+    async getLearningObjectsFromPath(id: LearningPathIdentifier): Promise<FilteredLearningObject[]> {
         return getProvider(id).getLearningObjectsFromPath(id);
     },
 
     /**
      * Fetch only learning object HRUIDs
      */
-    getLearningObjectIdsFromPath(id: LearningPathIdentifier): Promise<string[]> {
+    async getLearningObjectIdsFromPath(id: LearningPathIdentifier): Promise<string[]> {
         return getProvider(id).getLearningObjectIdsFromPath(id);
     },
 
     /**
      * Obtain a HTML-rendering of the learning object with the given identifier (as a string).
      */
-    getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
+    async getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
         return getProvider(id).getLearningObjectHTML(id);
     },
 };

backend/src/services/learning-objects/processing/audio/audio-processor.ts

@@ -14,7 +14,7 @@ class AudioProcessor extends StringProcessor {
         super(DwengoContentType.AUDIO_MPEG);
     }
 
-    protected renderFn(audioUrl: string): string {
+    override renderFn(audioUrl: string): string {
         return DOMPurify.sanitize(`<audio controls>
             <source src="${audioUrl}" type=${type}>
             Your browser does not support the audio element.

backend/src/services/learning-objects/processing/extern/extern-processor.ts

@@ -15,7 +15,7 @@ class ExternProcessor extends StringProcessor {
         super(DwengoContentType.EXTERN);
     }
 
-    override renderFn(externURL: string) {
+    override renderFn(externURL: string): string {
         if (!isValidHttpUrl(externURL)) {
             throw new ProcessingError('The url is not valid: ' + externURL);
         }