(function () {
  var STORAGE_KEY = "zhihua-theme-mode";
  var MODES = ["auto", "light", "dark"];

  function normalize(mode) {
    return MODES.indexOf(mode) >= 0 ? mode : "auto";
  }

  function readMode() {
    try {
      return normalize(localStorage.getItem(STORAGE_KEY));
    } catch (error) {
      return "auto";
    }
  }

  function applyMode(mode) {
    var normalized = normalize(mode);
    document.documentElement.setAttribute("data-theme", normalized);
    try {
      localStorage.setItem(STORAGE_KEY, normalized);
    } catch (error) {
      /* ignore */
    }
    updateButtons(normalized);
  }

  function updateButtons(mode) {
    document.querySelectorAll("[data-theme-mode]").forEach(function (button) {
      var active = button.getAttribute("data-theme-mode") === mode;
      button.classList.toggle("active", active);
      button.setAttribute("aria-pressed", active ? "true" : "false");
    });
  }

  function bindControls() {
    document.querySelectorAll("[data-theme-mode]").forEach(function (button) {
      button.addEventListener("click", function () {
        applyMode(button.getAttribute("data-theme-mode"));
      });
    });
  }

  applyMode(readMode());
  document.addEventListener("DOMContentLoaded", bindControls);
})();