[oden] Memoize textures by path

src/assets.ts

@@ -1,7 +1,14 @@
 import * as io from "./io.ts";
 import * as gfx from "./graphics.ts";
 
-export async function load_texture(path: string): Promise<gfx.Texture> {
-  const buffer = await io.load(path);
-  return gfx.create_texture(buffer, path);
+const LOADED_TEXTURES = new Map<string, Promise<gfx.Texture>>();
+
+export function load_texture(path: string): Promise<gfx.Texture> {
+  let promise = LOADED_TEXTURES.get(path);
+  if (!promise) {
+    promise = io.load(path).then((buffer) => gfx.create_texture(buffer, path));
+    LOADED_TEXTURES.set(path, promise);
+  }
+
+  return promise;
 }