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/api/evaluate/writing.ts

@@ -1,15 +1,20 @@
 // Next.js API route support: https://nextjs.org/docs/api-routes/introduction
 import type {NextApiRequest, NextApiResponse} from "next";
-import {getFirestore, doc, getDoc} from "firebase/firestore";
+import {getFirestore, doc, getDoc, setDoc} from "firebase/firestore";
 import {withIronSessionApiRoute} from "iron-session/next";
 import {sessionOptions} from "@/lib/session";
 import axios, {AxiosResponse} from "axios";
+import {app} from "@/firebase";
+import {Stat} from "@/interfaces/user";
+import {writingReverseMarking} from "@/utils/score";
 
 interface Body {
 	question: string;
 	answer: string;
+	id: string;
 }
 
+const db = getFirestore(app);
 export default withIronSessionApiRoute(handler, sessionOptions);
 
 async function handler(req: NextApiRequest, res: NextApiResponse) {
@@ -18,9 +23,27 @@ async function handler(req: NextApiRequest, res: NextApiResponse) {
 		return;
 	}
 
-	const backendRequest = await evaluate(req.body as Body);
+	res.status(200).json(null);
 
-	res.status(backendRequest.status).json(backendRequest.data);
+	console.log("🌱 - Still processing");
+	const backendRequest = await evaluate(req.body as Body);
+	console.log("🌱 - Process complete");
+
+	const correspondingStat = (await getDoc(doc(db, "stats", req.body.id))).data() as Stat;
+	const solutions = correspondingStat.solutions.map((x) => ({...x, evaluation: backendRequest.data}));
+	await setDoc(
+		doc(db, "stats", (req.body as Body).id),
+		{
+			solutions,
+			score: {
+				correct: writingReverseMarking[backendRequest.data.overall],
+				total: 100,
+				missing: 0,
+			},
+		},
+		{merge: true},
+	);
+	console.log("🌱 - Updated the DB");
 }
 
 async function evaluate(body: Body): Promise<AxiosResponse> {