/**
 * Detects preferred style variant and sets the "style_variant" cookie accordingly.
 * Reloads the page if the variant changes.
 */

(function () {
  function getCookie(name) {
    const match = document.cookie.split('; ').find(r => r.startsWith(name + '='));
    return match ? decodeURIComponent(match.split('=')[1]) : '';
  }

  function setCookie(name, value, maxAgeSeconds) {
    document.cookie = name + '=' + encodeURIComponent(value) + '; path=/; max-age=' + maxAgeSeconds;
  }

  function getUrlParam(name) {
    try {
      return new URLSearchParams(window.location.search).get(name) || '';
    } catch (e) {
      return '';
    }
  }

  const urlStyle = getUrlParam('style');
  const current = getCookie('style_variant');
  const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
  const desired = prefersDark ? '01-evening' : 'default';
  const MAX_AGE = 31536000; // 1 year

  // If URL parameter is present
  if (urlStyle) {
    if (current !== urlStyle) {
      setCookie('style_variant', urlStyle, MAX_AGE);
      location.reload();
    }
    return;
  }

  // No cookie yet -> set according to preference
  if (!current) {
    setCookie('style_variant', desired, MAX_AGE);
    location.reload();
    return;
  }

  // If cookie already equals desired, nothing to do
  if (current === desired) {
    return;
  }

  // Allow automatic switching between default and 01-evening based on preference
  if ((current === 'default' || current === '01-evening') && desired !== current) {
    setCookie('style_variant', desired, MAX_AGE);
    location.reload();
    return;
  }

  // Cookie contains another custom variant -> do not override automatically
})();