Separate get exam bussiness logic into a backend asset

src/pages/api/exam/[module]/index.ts

@@ -1,14 +1,11 @@
 // Next.js API route support: https://nextjs.org/docs/api-routes/introduction
 import type {NextApiRequest, NextApiResponse} from "next";
 import {app} from "@/firebase";
-import {getFirestore, collection, getDocs, query, where, setDoc, doc} from "firebase/firestore";
+import {getFirestore, setDoc, doc} from "firebase/firestore";
 import {withIronSessionApiRoute} from "iron-session/next";
 import {sessionOptions} from "@/lib/session";
-import {shuffle} from "lodash";
 import {Exam} from "@/interfaces/exam";
-import {Stat} from "@/interfaces/user";
+import { getExams } from "@/utils/exams.be";
-import {v4} from "uuid";
-
 const db = getFirestore(app);
 
 export default withIronSessionApiRoute(handler, sessionOptions);
@@ -26,31 +23,12 @@ async function GET(req: NextApiRequest, res: NextApiResponse) {
 		return;
 	}
 
-	const {module, avoidRepeated} = req.query as {module: string; avoidRepeated: string};
+	const {
-	const moduleRef = collection(db, module);
-
-	const q = query(moduleRef, where("isDiagnostic", "==", false));
-	const snapshot = await getDocs(q);
-
-	const exams: Exam[] = shuffle(
-		snapshot.docs.map((doc) => ({
-			id: doc.id,
-			...doc.data(),
 		module,
-		})),
+		avoidRepeated,
-	) as Exam[];
+	} = req.query as {module: string; avoidRepeated: string};
-
-	if (avoidRepeated === "true") {
-		const statsQ = query(collection(db, "stats"), where("user", "==", req.session.user.id));
-		const statsSnapshot = await getDocs(statsQ);
-
-		const stats: Stat[] = statsSnapshot.docs.map((doc) => ({id: doc.id, ...doc.data()})) as unknown as Stat[];
-		const filteredExams = exams.filter((x) => !stats.map((s) => s.exam).includes(x.id));
-
-		res.status(200).json(filteredExams.length > 0 ? filteredExams : exams);
-		return;
-	}
 
+	const exams: Exam[] = await getExams(db, module, avoidRepeated, req.session.user.id);
 	res.status(200).json(exams);
 }
 

src/utils/exams.be.ts

@@ -0,0 +1,52 @@
+import {
+  collection,
+  getDocs,
+  query,
+  where,
+  setDoc,
+  doc,
+  Firestore,
+} from "firebase/firestore";
+import { shuffle } from "lodash";
+import { Exam } from "@/interfaces/exam";
+import { Stat } from "@/interfaces/user";
+
+export const getExams = async (
+  db: Firestore,
+  module: string,
+  avoidRepeated: string,
+  // added userId as due to assignments being set from the teacher to the student
+  // we need to make sure we are serving exams not executed by the user and not
+  // by the teacher that performed the request
+  userId: string
+): Promise<Exam[]> => {
+  const moduleRef = collection(db, module);
+
+  const q = query(moduleRef, where("isDiagnostic", "==", false));
+  const snapshot = await getDocs(q);
+
+  const exams: Exam[] = shuffle(
+    snapshot.docs.map((doc) => ({
+      id: doc.id,
+      ...doc.data(),
+      module,
+    }))
+  ) as Exam[];
+
+  if (avoidRepeated === "true") {
+    const statsQ = query(collection(db, "stats"), where("user", "==", userId));
+    const statsSnapshot = await getDocs(statsQ);
+
+    const stats: Stat[] = statsSnapshot.docs.map((doc) => ({
+      id: doc.id,
+      ...doc.data(),
+    })) as unknown as Stat[];
+    const filteredExams = exams.filter(
+      (x) => !stats.map((s) => s.exam).includes(x.id)
+    );
+
+    return filteredExams.length > 0 ? filteredExams : exams;
+  }
+
+  return exams;
+};