Refactored evaluation process for improved efficiency:

- Initial response set to null; Frontend now generates a list of anticipated stats;
- Background evaluation dynamically updates DB upon completion;
- Frontend actively monitors and finalizes upon stat evaluation completion.

src/pages/(exam)/ExamPage.tsx

@@ -37,6 +37,7 @@ export default function ExamPage({page}: Props) {
 	const [showAbandonPopup, setShowAbandonPopup] = useState(false);
 	const [avoidRepeated, setAvoidRepeated] = useState(false);
 	const [timeSpent, setTimeSpent] = useState(0);
+	const [statsAwaitingEvaluation, setStatsAwaitingEvaluation] = useState<string[]>([]);
 
 	const [exams, setExams] = useExamStore((state) => [state.exams, state.setExams]);
 	const [userSolutions, setUserSolutions] = useExamStore((state) => [state.userSolutions, state.setUserSolutions]);
@@ -94,6 +95,7 @@ export default function ExamPage({page}: Props) {
 		if (selectedModules.length > 0 && exams.length !== 0 && moduleIndex >= selectedModules.length && !hasBeenUploaded && !showSolutions) {
 			const newStats: Stat[] = userSolutions.map((solution) => ({
 				...solution,
+				id: solution.id || uuidv4(),
 				timeSpent,
 				session: sessionId,
 				exam: solution.exam!,
@@ -111,6 +113,41 @@ export default function ExamPage({page}: Props) {
 		// eslint-disable-next-line react-hooks/exhaustive-deps
 	}, [selectedModules, moduleIndex, hasBeenUploaded]);
 
+	useEffect(() => {
+		if (statsAwaitingEvaluation.length === 0) return setIsEvaluationLoading(false);
+		return setIsEvaluationLoading(true);
+	}, [statsAwaitingEvaluation]);
+
+	useEffect(() => {
+		if (statsAwaitingEvaluation.length > 0) {
+			statsAwaitingEvaluation.forEach(checkIfStatHasBeenEvaluated);
+		}
+		// eslint-disable-next-line react-hooks/exhaustive-deps
+	}, [statsAwaitingEvaluation]);
+
+	const checkIfStatHasBeenEvaluated = (id: string) => {
+		setTimeout(async () => {
+			const statRequest = await axios.get<Stat>(`/api/stats/${id}`);
+			const stat = statRequest.data;
+			if (stat.solutions.every((x) => x.evaluation !== null)) {
+				const userSolution: UserSolution = {
+					id,
+					exercise: stat.exercise,
+					score: stat.score,
+					solutions: stat.solutions,
+					type: stat.type,
+					exam: stat.exam,
+					module: stat.module,
+				};
+
+				setUserSolutions(userSolutions.map((x) => (x.exercise === userSolution.exercise ? userSolution : x)));
+				return setStatsAwaitingEvaluation((prev) => prev.filter((x) => x !== id));
+			}
+
+			return checkIfStatHasBeenEvaluated(id);
+		}, 5 * 1000);
+	};
+
 	const updateExamWithUserSolutions = (exam: Exam): Exam => {
 		if (exam.module === "reading" || exam.module === "listening") {
 			const parts = exam.parts.map((p) =>
@@ -137,20 +174,19 @@ export default function ExamPage({page}: Props) {
 
 			Promise.all(
 				exam.exercises.map(async (exercise) => {
-					if (exercise.type === "writing") {
-						return await evaluateWritingAnswer(exercise, solutions.find((x) => x.exercise === exercise.id)!);
-					}
+					const evaluationID = uuidv4();
+					if (exercise.type === "writing")
+						return await evaluateWritingAnswer(exercise, solutions.find((x) => x.exercise === exercise.id)!, evaluationID);
 
-					if (exercise.type === "interactiveSpeaking" || exercise.type === "speaking") {
-						return await evaluateSpeakingAnswer(exercise, solutions.find((x) => x.exercise === exercise.id)!);
-					}
+					if (exercise.type === "interactiveSpeaking" || exercise.type === "speaking")
+						return await evaluateSpeakingAnswer(exercise, solutions.find((x) => x.exercise === exercise.id)!, evaluationID);
 				}),
 			)
 				.then((responses) => {
+					setStatsAwaitingEvaluation((prev) => [...prev, ...responses.filter((x) => !!x).map((r) => (r as any).id)]);
 					setUserSolutions([...userSolutions, ...responses.filter((x) => !!x)] as any);
 				})
 				.finally(() => {
-					setIsEvaluationLoading(false);
 					setHasBeenUploaded(false);
 				});
 		}