feat(platform): add assets cache to ImageLoader

Author: RuggeroVisintin

src/platform/gfx/ImageLoader.ts

@@ -6,18 +6,24 @@ import { ImageAsset } from "./ImageAsset";
  * Loads a given image asset
  */
 export class ImageLoader {
+    private _assetsCache: Record<string, ImageAsset> = {};
+
     public async load(src: string): Promise<ImageAsset> {
+        if (this._assetsCache[src]) return this._assetsCache[src];
+
         return new Promise((resolve, reject) => {  
             const type = this.getTypeFromFileName(src);
 
             const image = new Image();
             image.onerror = reject;
 
             image.onload = async () => {
-                resolve(new ImageAsset(
+                this._assetsCache[src] = new ImageAsset(
                     await createImageBitmap(image), 
                     type
-                ));
+                );
+
+                resolve(this._assetsCache[src]);
             };
 
             image.src = src;

test/unit/platform/gfx/ImageLoader.test.ts

@@ -22,5 +22,24 @@ describe('platform/gfx/ImageLoader', () => {
                 await imageLoader.load('test.png');
             }).rejects.toThrow('Error');
         })
+
+        it('Should cache assets that are already loaded', async () => {
+            const spy = jest.fn().mockResolvedValueOnce(() => { });
+            
+            global.Image = jest.fn().mockImplementation(() => ({
+                onload: jest.fn(),
+                set src(value: string) { 
+                    spy();
+                    this.onload();
+                }
+            }))
+
+            const imageLoader = new ImageLoader();
+
+            await imageLoader.load('test.png');
+            await imageLoader.load('test.png');
+
+            expect(spy).toHaveBeenCalledTimes(1);
+        })
     })
 })