export default function debounce(fn, delay) {
  // TODO: Return a debounced function that delays execution until delay ms have passed
  throw new Error('Not implemented');
}

import debounce from './debounce';

const wait = (ms) => new Promise((r) => setTimeout(r, ms));

describe('debounce', () => {
  test('calls function after delay', async () => {
    let calls = 0;
    const debounced = debounce(() => { calls += 1; }, 120);

    debounced();
    expect(calls).toBe(0);

    await wait(140);
    expect(calls).toBe(1);
  });

  test('resets timer on rapid calls (only last executes)', async () => {
    let calls = 0;
    const debounced = debounce(() => { calls += 1; }, 100);

    debounced();
    await wait(50);
    debounced();
    await wait(50);
    debounced();

    await wait(90);
    expect(calls).toBe(0);

    await wait(20);
    expect(calls).toBe(1);
  });

  test('passes arguments (and preserves this via apply)', async () => {
    let last = '';
    const debounced = debounce(function (name) {
      last = `Hi ${name}`;
    }, 80);

    debounced.call({ tag: 'ctx' }, 'Alice');
    await wait(100);
    expect(last).toBe('Hi Alice');
  });
});