window.addEventListener('DOMContentLoaded', () => {
  const storageTheme = window.localStorage?.getItem('theme');
  const preferesDark = window.matchMedia('(prefers-color-scheme: dark)').matches;

  let isDark = preferesDark;

  const hid = document.querySelector('#hid');
  const html = document.querySelector('html');
  const aside = document.querySelector('#side-bar');
  const sidenotes = document.querySelector('.sidenotes');
  const harr = document.querySelector('#harr');

  if (storageTheme === 'dark' || storageTheme === 'light') {
    const theme = storageTheme;
    isDark = storageTheme === 'dark';
    hid.classList.add(theme);
    html.classList.add(theme);
    aside.classList.add(theme);
    sidenotes.classList.add(theme);
    harr.classList.add(theme);

    for (const article of document.querySelectorAll('article')) {
      article.classList.add(theme);
    }
  }

  function toogleTheme() {
    const arg = isDark ? ['dark', 'light'] : ['light', 'dark'];
    const theme = arg[1];

    if (!hid.classList.replace(...arg)) {
      hid.classList.add(theme);
    }

    if (!html.classList.replace(...arg)) {
      html.classList.add(theme);
    }

    if (!aside.classList.replace(...arg)) {
      aside.classList.add(theme);
    }

    if (!sidenotes.classList.replace(...arg)) {
      sidenotes.classList.add(theme);
    }

    if (!harr.classList.replace(...arg)) {
      harr.classList.add(theme);
    }

    for (const article of document.querySelectorAll('article')) {
      if (!article.classList.replace(...arg)) {
        article.classList.add(theme);
      }
    }

    isDark = !isDark;
    if (window.localStorage) {
      window.localStorage.setItem('theme', isDark ? 'dark' : 'light');
    }
  }

  const sun = document.querySelector('.sun');
  const moon = document.querySelector('.moon');

  sun.addEventListener('click', toogleTheme);
  moon.addEventListener('click', toogleTheme);

  if (isDark) {
    hid.classList.add('dark');
  } else {
    hid.classList.add('light');
  }
});