(function () {
  const KEY = "frenchJourney.theme";
  const root = document.documentElement;

  function apply(theme) {
    root.dataset.theme = theme;
    localStorage.setItem(KEY, theme);
    const button = document.querySelector("[data-theme-toggle]");
    if (button) {
      const dark = theme === "dark";
      button.textContent = dark ? "Light" : "Dark";
      button.setAttribute("aria-pressed", String(dark));
    }
  }

  const saved = localStorage.getItem(KEY);
  const preferred = window.matchMedia && window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light";
  apply(saved || preferred);

  window.addEventListener("DOMContentLoaded", () => {
    const button = document.querySelector("[data-theme-toggle]");
    if (!button) return;
    button.onclick = () => apply(root.dataset.theme === "dark" ? "light" : "dark");
    apply(root.dataset.theme || "light");
  });
})();