nEngine/packages/render/test/asset-coordinator.test.ts

import { describe, expect, it } from "vitest";
import type { AssetEntry } from "@nengine/core";
import { AssetCoordinator, MAX_ASSET_REQUEST_IDS } from "../src/sync/asset-coordinator.js";

const index = (ids: string[]): Record<string, { kind: "image" | "audio"; mime: string; size: number }> => {
  const out: Record<string, { kind: "image" | "audio"; mime: string; size: number }> = {};
  for (const id of ids) out[id] = { kind: "image", mime: "image/png", size: 1 };
  return out;
};

const entry = (id: string): Record<string, AssetEntry> => ({ [id]: { kind: "image", mime: "image/png", data: "x" } });

describe("AssetCoordinator (D37 on-demand asset requests)", () => {
  it("requests only wanted ids known to the server index", () => {
    const c = new AssetCoordinator();
    c.setIndex(index(["grass-1", "water-1"]));
    c.want(["grass-1", "water-1", "missing-asset"]);
    expect(c.requestBatch()).toEqual(["grass-1", "water-1"]);
    expect(c.requestBatch()).toEqual([]);
  });

  it("dedupes: never re-requests ids that are pending or loaded", () => {
    const c = new AssetCoordinator();
    c.setIndex(index(["a", "b", "c"]));
    c.want(["a", "b", "c"]);
    const batch1 = c.requestBatch();
    expect(batch1).toEqual(["a", "b", "c"]);
    // all pending — nothing new
    expect(c.requestBatch()).toEqual([]);
    // a response for a and b arrives; c's request is still in flight
    c.applyAssets({ ...entry("a"), ...entry("b") });
    expect(c.has("a")).toBe(true);
    expect(c.has("b")).toBe(true);
    expect(c.has("c")).toBe(false);
    expect(c.requestBatch()).toEqual([]); // c still pending
    // c's response arrives — nothing left to request
    c.applyAssets(entry("c"));
    expect(c.has("c")).toBe(true);
    expect(c.requestBatch()).toEqual([]);
  });

  it("caps a batch at MAX_ASSET_REQUEST_IDS", () => {
    const ids = Array.from({ length: MAX_ASSET_REQUEST_IDS + 10 }, (_, i) => `a${i}`);
    const c = new AssetCoordinator();
    c.setIndex(index(ids));
    c.want(ids);
    const batch = c.requestBatch();
    expect(batch).toHaveLength(MAX_ASSET_REQUEST_IDS);
    const rest = c.requestBatch();
    expect(rest).toHaveLength(10);
  });

  it("new wanted ids from a later snapshot are requested after a prior batch resolved", () => {
    const c = new AssetCoordinator();
    c.setIndex(index(["a"]));
    c.want(["a"]);
    expect(c.requestBatch()).toEqual(["a"]);
    c.applyAssets(entry("a"));
    // a fresh snapshot adds a new referenced asset
    c.setIndex(index(["a", "b"]));
    c.want(["b"]);
    expect(c.requestBatch()).toEqual(["b"]);
  });

  it("applyAssets with an empty frame changes nothing", () => {
    const c = new AssetCoordinator();
    c.setIndex(index(["a"]));
    c.want(["a"]);
    expect(c.requestBatch()).toEqual(["a"]);
    c.applyAssets({});
    expect(c.has("a")).toBe(false);
    expect(c.requestBatch()).toEqual([]); // still pending until a response arrives
  });
});