refactor(api, curriculum): use the shared shuffleArray util (#56444)

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

api-server/src/server/utils/exam.js

@@ -1,18 +1,4 @@
-function shuffleArray(arr) {
-  let currentIndex = arr.length,
-    randomIndex;
-
-  while (currentIndex != 0) {
-    randomIndex = Math.floor(Math.random() * currentIndex);
-    currentIndex--;
-    [arr[currentIndex], arr[randomIndex]] = [
-      arr[randomIndex],
-      arr[currentIndex]
-    ];
-  }
-
-  return arr;
-}
+import { shuffleArray } from '../../../../shared/utils/shuffle-array';
 
 function filterDeprecated(arr) {
   return arr.filter(i => !i.deprecated);

api/src/utils/exam.ts

@@ -1,23 +1,7 @@
 import { Exam, Question } from '@prisma/client';
+import { shuffleArray } from './../../../shared/utils/shuffle-array';
 import { UserExam, GeneratedExam } from './exam-types';
 
-function shuffleArray<T>(arr: T[]): T[] {
-  let currentIndex: number = arr.length;
-  let randomIndex: number;
-
-  while (currentIndex !== 0) {
-    randomIndex = Math.floor(Math.random() * currentIndex);
-    currentIndex--;
-
-    [arr[currentIndex], arr[randomIndex]] = [
-      arr[randomIndex] as T,
-      arr[currentIndex] as T
-    ];
-  }
-
-  return arr;
-}
-
 /**
  * Remove objects from array with deprecated: true.
  *

curriculum/test/utils/sort-challenges.test.js

@@ -1,3 +1,4 @@
+const { shuffleArray } = require('../../../shared/utils/shuffle-array');
 const { sortChallenges } = require('./sort-challenges');
 
 const challenges = [
@@ -222,7 +223,7 @@ const challenges = [
 describe('sortChallenges', () => {
   it('sorts challenges by superblock, block and challenge order', () => {
     const copyOfChallenges = [...challenges];
-    shuffle(copyOfChallenges);
+    shuffleArray(copyOfChallenges);
     const actualChallenges = sortChallenges(copyOfChallenges);
 
     expect(actualChallenges).toEqual(challenges);
@@ -241,11 +242,3 @@ describe('sortChallenges', () => {
     expect(actualChallenges[0]).not.toEqual(copyOfChallenges[0]);
   });
 });
-
-// Use the Fisher–Yates shuffle algorithm to shuffle array
-const shuffle = arr => {
-  for (let i = arr.length - 1; i > 0; i--) {
-    const j = Math.floor(Math.random() * (i + 1));
-    [arr[i], arr[j]] = [arr[j], arr[i]];
-  }
-};

shared/utils/shuffle-array.ts

@@ -4,7 +4,10 @@ export const shuffleArray = <T>(arrToShuffle: Array<T>) => {
 
   for (let i = arr.length - 1; i > 0; i--) {
     const j = Math.floor(Math.random() * (i + 1));
-    [arr[i], arr[j]] = [arr[j], arr[i]];
+
+    // We know that i and j are within the bounds of the array, TS doesn't
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
+    [arr[i], arr[j]] = [arr[j]!, arr[i]!];
   }
 
   return arr;