Separate get exam bussiness logic into a backend asset

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;
+};