import { expect, test } from "bun:test";
import { LazyPromise } from "./LazyPromise";

test("normal `Promise` is *not* lazy", async () => {
  let started = false;
  const promise = new Promise((resolve, _reject) => {
    started = true;
    resolve("foo");
  });
  expect(started).toBe(true);
  expect(await promise).toEqual("foo");
});

test("`LazyPromise` is lazy", async () => {
  let started = false;
  const promise = new LazyPromise(() => {
    started = true;
    return "foo";
  });
  expect(started).toBe(false);
  await promise;
  expect(started).toBe(true);
  expect(await promise).toEqual("foo");
});

test("`LazyPromise` can reject", async () => {
  let started = false;
  const promise = new LazyPromise(() => {
    started = true;
    throw new Error("oops");
  });
  expect(started).toBe(false);
  expect(async () => promise).toThrow("oops");
  expect(started).toBe(true);
});

test("`LazyPromise` supports `.finally(…)` and `.catch(…)`", async () => {
  let started = false;
  const { promise: reachedFinally, resolve: resolveFinally } =
    Promise.withResolvers<string>();
  const promise = new LazyPromise(() => {
    started = true;
    throw new Error("oops");
  });
  expect(started).toBe(false);
  expect(async () => promise).toThrow("oops");
  expect(started).toBe(true);
  void promise
    .finally(() => {
      resolveFinally("hello");
    })
    .catch(() => {});
  expect(await reachedFinally).toEqual("hello");
});