function wait (ms) {
  return new Promise(resolve => setTimeout(() => resolve(), ms));
}

export default async function capture(browser, url) {
  // Load the specified page
  const page = await browser.newPage();
  await page.goto(url, {waitUntil: 'load'});

  // Get the height of the rendered page
  const bodyHandle = await page.$('body');
  const { height } = await bodyHandle.boundingBox();
  await bodyHandle.dispose();

  // Scroll one viewport at a time, pausing to let content load
  const viewportHeight = page.viewport().height;
  let viewportIncr = 0;
  while (viewportIncr + viewportHeight < height) {
    await page.evaluate(_viewportHeight => {
      window.scrollBy(0, _viewportHeight);
    }, viewportHeight);
    await wait(20);
    viewportIncr = viewportIncr + viewportHeight;
  }

  // Scroll back to top
  await page.evaluate(_ => {
    window.scrollTo(0, 0);
  });

  // Some extra delay to let images load
  await wait(100);

  return await page.screenshot({type: 'png'});
}