function getPos(element) {
  /* Element.getBoundingClientRect()
   * Return box of the element relatively to viewport.
   */
  const rect = element.getBoundingClientRect();

  /* The properties window.scrollX and window.scrollY
   * return the viewport position relatively to the document
   */
  return {
    x: rect.left + window.scrollX,
    y: rect.top + window.scrollY,
  };
}

// Use this if needed :
// const getTop = element => element.offsetTop + (element.offsetParent && getTop(element.offsetParent));
let sidenotes;
const resize = () => {
  for (const sidenote of sidenotes) {
    if (sidenote.offsetWidth < 200 || window.screen.width < 1400) {
      sidenote.innerHTML = '';
      return;
    }

    const articleRef = sidenote.attributes.for.value;
    const article = document.querySelector(`#${CSS.escape(articleRef)}`);
    const notes = Array.from(article.querySelectorAll('li'))
      .filter(element => element.id.startsWith('user-content-fn'));
    const newSidenotes = notes.map(sidenoteLi => {
      const div = document.createElement('div');
      const refName = sidenoteLi.querySelector('.data-footnote-backref').attributes.href.value;
      const refSideNode = article.querySelector(refName);

      const sup = document.createElement('sup');
      sup.textContent = refSideNode.textContent + ' ';

      for (const element of sidenoteLi.children) {
        const child = element.cloneNode(true);
        div.append(child);
      }

      div.children[0].prepend(sup);
      div.style.top = `${getPos(refSideNode).y}px`;
      div.classList.add('sidenote');

      return div;
    });

    sidenote.replaceChildren(...newSidenotes);

    if (sidenote.offsetWidth < 100 || window.screen.width < 1400) {
      sidenote.innerHTML = '';
      return;
    }
  }
};

window.addEventListener('DOMContentLoaded', () => {
  sidenotes = document.querySelectorAll('.sidenotes');
  if (sidenotes.length > 0) {
    new ResizeObserver(resize).observe(sidenotes[0]);
  }

  if (document.querySelectorAll('.math-display').length > 0) {
    document.head.innerHTML += '<link href="/s/css/katex.css" rel="stylesheet"/>';
  }
});