Stop StoneHandler.getFoilStones() from mutating shared level data

src/components/stone-handler/stone-handler.spec.ts

@@ -139,6 +139,34 @@ describe('StoneHandler - Latest Optimizations', () => {
     });
   });
 
+  describe('getFoilStones - shared level data integrity', () => {
+    it('does not mutate the foilStones array on the shared level data', () => {
+      const levelData = {
+        puzzles: [{ targetStones: ['A', 'B'], foilStones: ['C', 'D', 'E'] }],
+      };
+      const originalFoilStones = [...levelData.puzzles[0].foilStones];
+
+      const handler = new StoneHandler(mockContext, mockCanvas, 0, levelData);
+      // The puzzle_completed analytics event reads the foil stones more than once.
+      handler.getFoilStones();
+      handler.getFoilStones();
+
+      expect(levelData.puzzles[0].foilStones).toEqual(originalFoilStones);
+    });
+
+    it('does not drop foil stones from level data when a puzzle has more than eight stones', () => {
+      const levelData = {
+        puzzles: [{ targetStones: ['A'], foilStones: ['B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J'] }],
+      };
+      const originalFoilStones = [...levelData.puzzles[0].foilStones];
+
+      const handler = new StoneHandler(mockContext, mockCanvas, 0, levelData);
+      handler.getFoilStones();
+
+      expect(levelData.puzzles[0].foilStones).toEqual(originalFoilStones);
+    });
+  });
+
   describe('Performance Improvements', () => {
     it('should skip disposed stones in draw loop', () => {
       const mockStones = [

src/components/stone-handler/stone-handler.ts

@@ -252,27 +252,30 @@ export default class StoneHandler {
   }
 
   public getFoilStones() {
-    this.currentPuzzleData.targetStones.forEach((e) => {
-      const index = this.currentPuzzleData.foilStones.indexOf(e);
+    const targetStones = this.currentPuzzleData.targetStones;
+    // Work on a copy so the shared level data (currentPuzzleData.foilStones) is never mutated.
+    const foilStones = [...this.currentPuzzleData.foilStones];
+
+    targetStones.forEach((e) => {
+      const index = foilStones.indexOf(e);
       if (index !== -1) {
-        this.currentPuzzleData.foilStones.splice(index, 1);
+        foilStones.splice(index, 1);
       }
     });
 
-    const totalStonesCount =
-      this.currentPuzzleData.targetStones.length +
-      this.currentPuzzleData.foilStones.length;
+    const totalStonesCount = targetStones.length + foilStones.length;
 
     if (totalStonesCount > 8) {
       const extraStonesCount = totalStonesCount - 8;
 
-      this.currentPuzzleData.foilStones.splice(0, extraStonesCount);
+      foilStones.splice(0, extraStonesCount);
     }
 
-    this.currentPuzzleData.targetStones.forEach((e) => {
-      this.currentPuzzleData.foilStones.push(e);
+    targetStones.forEach((e) => {
+      foilStones.push(e);
     });
-    return this.currentPuzzleData.foilStones.sort(() => Math.random() - 0.5);
+
+    return foilStones.sort(() => Math.random() - 0.5);
   }
 
   /**

src/scenes/gameplay-scene/gameplay-flow-manager.ts

@@ -492,6 +492,7 @@ export class GameplayFlowManager {
         const itemSelected = puzzleType === "Word"
           ? (droppedLetters ?? "TIMEOUT")
           : (pickedStone?.text ?? "TIMEOUT");
+        const foilStones = this.stoneHandler.getFoilStones();
 
         this.analyticsIntegration.track(
             AnalyticsEventType.PUZZLE_COMPLETED,
@@ -503,9 +504,7 @@ export class GameplayFlowManager {
                 puzzle_number: this.currentPuzzleIndex,
                 item_selected: itemSelected,
                 target: this.stoneHandler.getCorrectTargetStone(),
-                foils: Array.isArray(this.stoneHandler.getFoilStones())
-                    ? this.stoneHandler.getFoilStones().join(',')
-                    : this.stoneHandler.getFoilStones(),
+                foils: Array.isArray(foilStones) ? foilStones.join(',') : foilStones,
                 response_time: (endTime - this.puzzleTime) / 1000,
             }
         );