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import { describe, expect, mock, test } from "bun:test";

import { asyncDerived } from "../src/async.js";
import { signal } from "../src/signals.js";

function sleep(ms: number): Promise<void> {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve();
    }, ms);
  });
}

describe("asyncDerived", () => {
  test("should return pending state as an initial state", () => {
    const $c = asyncDerived(() => {
      return new Promise(() => {});
    });

    expect($c.get().isSettled).toBe(false);
  });

  test("should change to resolved state when the promise is resolved", async () => {
    const p = new Promise<void>((resolve) => {
      resolve();
    });

    const $c = asyncDerived(() => {
      return p;
    });

    await p;

    expect($c.get().isResolved).toBe(true);
  });

  test("should change to rejected state when the promise is rejected", async () => {
    const p = new Promise<void>((_, reject) => {
      reject(new Error("Sample Error"));
    });

    const $c = asyncDerived(() => {
      return p;
    });

    await p.catch(() => {});

    expect($c.get().isRejected).toBe(true);
  });

  test("should re-run when the inner dependencies got update", async () => {
    const $s = signal(1);

    const $c = asyncDerived(async (ctx) => {
      return $s.get(ctx) + 1;
    });

    await sleep(1);

    expect($c.get().isResolved).toBe(true);
    expect(($c.get() as any).data).toBe(2);

    $s.set(2);

    await sleep(1);

    expect($c.get().isResolved).toBe(true);
    expect(($c.get() as any).data).toBe(3);
  });

  test("should notify abort via AbortSignal", async () => {
    const fn = mock((_n: number) => {});
    const $s = signal(1);

    asyncDerived(async (ctx, abortSignal) => {
      const n = $s.get(ctx);

      abortSignal.addEventListener(
        "abort",
        () => {
          fn(n);
        },
        { once: true },
      );

      return n + 1;
    });

    $s.set(2);
    $s.set(3);

    await sleep(1);

    expect(fn.mock.calls).toEqual([[1], [2]]);
  });
});