import { AsyncTaskQueue } from "../src/index";

test("example evaluates correctly", async () => {
  jest.useFakeTimers();

  const THROTTLE_DELAY_MS = 100;

  const q = new AsyncTaskQueue<number>(
    async () => {/* no-op */ },
  )
    // Handler will receive up to 4 items per batch.
    .batchSize(4)
    // Handler will be called at most once per 100 milliseconds.
    .throttleMs(THROTTLE_DELAY_MS);

  // Add items to the queue.
  for (let n = 0; n < 1000; n++) {
    q.push(n);
  }

  // Advance the clock incrementally and asynchronously so that we yield to the
  // task queue control loop frequently. This should allow it to complete its
  // work more or less as it would with real timers.
  //
  // Advance timers by a shorter duration than THROTTLE_DELAY_MS to test that
  // the task queue throttles correctly according to wall time and not merely
  // according to event loop ticks.
  const fakeTimerIncrementMs = Math.ceil(THROTTLE_DELAY_MS / 2);
  for (
    let mockDelayMs = 0;
    mockDelayMs < 4000;
    mockDelayMs += fakeTimerIncrementMs
  ) {
    await jest.advanceTimersByTimeAsync(fakeTimerIncrementMs);
  }

  expect(q.size()).toBeLessThan(850);
  expect(q.size()).toBeGreaterThan(825);

  q.drain();
  expect(q.size()).toEqual(0);
});