// A page whose rail sits in its flow must not be ready before the rail: the rail would then appear a
// moment after the page and shove its content sideways.
import { describe, expect, it } from "vitest";
import type { ComponentType } from "react";
import { lazyWithPreload, lazyWithPreloadAlongside } from "./lazyWithPreload";

const component = (() => null) as ComponentType<object>;

describe("lazyWithPreloadAlongside", () => {
  it("is ready only once its rail has loaded too", async () => {
    let releaseRail = () => {};
    const rail = lazyWithPreload(
      () =>
        new Promise<{ default: ComponentType<object> }>((resolve) => {
          releaseRail = () => resolve({ default: component });
        }),
    );
    const page = lazyWithPreloadAlongside(async () => ({ default: component }), rail);
    let pageReady = false;
    const loading = page.preload().then(() => {
      pageReady = true;
    });
    await new Promise((r) => setTimeout(r, 0));
    expect(pageReady).toBe(false); // its own code is in, its rail's is not
    releaseRail();
    await loading;
    expect(pageReady).toBe(true);
  });
});