type Theme = "light" | "dark";

const STORAGE_KEY = "theme";

const getSavedTheme = (): Theme => {
  const raw = localStorage.getItem(STORAGE_KEY);
  if (raw === "light" || raw === "dark") return raw;
  return "dark";
};

const applyTheme = (theme: Theme): void => {
  const html = document.documentElement;
  html.setAttribute("data-theme", theme);
  localStorage.setItem(STORAGE_KEY, theme);
  updateToggleButtons(theme);
};

const cycleTheme = (): void => {
  const current = getSavedTheme();
  const next: Theme = current === "light" ? "dark" : "light";
  applyTheme(next);
};

const updateToggleButtons = (theme: Theme): void => {
  const headerBtn = document.getElementById(
    "theme-toggle",
  ) as HTMLButtonElement | null;
  const footerBtn = document.getElementById(
    "footer-theme-toggle",
  ) as HTMLButtonElement | null;

  const updateButton = (btn: HTMLButtonElement | null): void => {
    if (!btn) return;

    const label = btn.querySelector("[data-theme-label]") as HTMLElement | null;
    if (label) {
      label.textContent = theme;
    }

    const svg = btn.querySelector("svg");
    if (!svg) return;

    if (theme === "light") {
      svg.innerHTML =
        '<circle cx="12" cy="12" r="5"/><path d="M12 1v2M12 21v2M4.22 4.22l1.42 1.42M18.36 18.36l1.42 1.42M1 12h2M21 12h2M4.22 19.78l1.42-1.42M18.36 5.64l1.42-1.42"/>';
      svg.setAttribute("stroke", "currentColor");
      svg.setAttribute("fill", "none");
    } else {
      svg.innerHTML =
        '<path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/>';
      svg.setAttribute("stroke", "currentColor");
      svg.setAttribute("fill", "none");
    }
  };

  updateButton(headerBtn);
  updateButton(footerBtn);
};

const initTheme = (): void => {
  const saved = getSavedTheme();
  applyTheme(saved);

  const headerBtn = document.getElementById(
    "theme-toggle",
  ) as HTMLButtonElement | null;
  const footerBtn = document.getElementById(
    "footer-theme-toggle",
  ) as HTMLButtonElement | null;

  if (headerBtn) {
    headerBtn.addEventListener("click", cycleTheme);
  }

  if (footerBtn) {
    footerBtn.addEventListener("click", cycleTheme);
  }
};

if (document.readyState === "loading") {
  document.addEventListener("DOMContentLoaded", initTheme);
} else {
  initTheme();
}