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 sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

describe('debounce', () => {
  test('does not call synchronously and runs after delay', async () => {
    const calls = [];
    const debounced = debounce((value) => { calls.push(value); }, 80);

    debounced('A');

    expect(calls).toEqual([]);

    await sleep(90);
    expect(calls).toEqual(['A']);
  });

  test('rapid calls only run the latest argument after the final delay', async () => {
    const calls = [];
    const debounced = debounce((value) => { calls.push(value); }, 100);

    debounced('A'); // t=0
    await sleep(50);
    debounced('B'); // t=50
    await sleep(40);
    debounced('C'); // t=90

    await sleep(95);
    expect(calls).toEqual([]);

    await sleep(20);
    expect(calls).toEqual(['C']);
  });

  test('preserves this context and arguments', async () => {
    const calls = [];
    const debounced = debounce(function (value) {
      calls.push(`${this.tag}:${value}`);
    }, 60);

    debounced.call({ tag: 'search-box' }, 'react');
    await sleep(80);

    expect(calls).toEqual(['search-box:react']);
  });
});