deck: Implemented Fisher-Yates shuffling algorithm to shuffle the deck

Fixes: #2

backend/tests/deck.test.ts

@@ -1,7 +1,28 @@
-import { makeCard } from '../uno-game-engine/deck';
+import { shuffle, makeCard } from '../uno-game-engine/deck';
 describe('testing deck.ts', () => {
     test('makeCard', () => {
         const card = makeCard('number', 'blue', '3');
         expect(card.color).toBe('blue');
     });
 });
+describe('shuffle function', () => {
+    test('should change order of elements', () => {
+        // Create a mock deck
+        const deck = [
+            makeCard('number', 'red', '1'),
+            makeCard('number', 'blue', '2'),
+            makeCard('number', 'red', '1'),
+            makeCard('number', 'yellow', '1'),
+        ];
+
+        // Create a copy of the deck for comparison
+        const originalDeck = [...deck];
+        shuffle(deck);
+
+        // Check that the order of elements has changed
+        const orderChanged = deck.some(
+            (card, index) => card !== originalDeck[index]
+        );
+        expect(orderChanged).toBe(true);
+    });
+});

backend/uno-game-engine/deck.ts

@@ -74,7 +74,10 @@ export function makeCard(
  * This function shuffles the elements of the given array *in place* . The function behaves in a type-agnostic way.
  * Time complexity: O(n)
  */
-export function shuffle(deck: Array<any>) {
-    //todo: Implement a generic shuffling algorithm
-    [deck[0], deck[1]] = [deck[1], deck[0]];
+export function shuffle(deck: Array<UNOCard>) {
+    // Fisher-Yates shuffle algorithm to shuffle card deck
+    for (let i = deck.length - 1; i > 0; i--) {
+        const j = Math.floor(Math.random() * i);
+        [deck[i], deck[j]] = [deck[j], deck[i]];
+    }
 }