export type ThemeMode = "light" | "dark";

export const THEME_STORAGE_KEY = "xunlou-theme";

export function isThemeMode(value: string | null | undefined): value is ThemeMode {
  return value === "light" || value === "dark";
}

export function readStoredTheme(): ThemeMode | null {
  if (typeof window === "undefined") return null;
  try {
    const stored = localStorage.getItem(THEME_STORAGE_KEY);
    return isThemeMode(stored) ? stored : null;
  } catch {
    return null;
  }
}

export function applyTheme(mode: ThemeMode) {
  document.documentElement.setAttribute("data-theme", mode);
  document.documentElement.style.colorScheme = mode;
}

export function persistTheme(mode: ThemeMode) {
  try {
    localStorage.setItem(THEME_STORAGE_KEY, mode);
  } catch {
    /* ignore quota / private mode */
  }
  applyTheme(mode);
}

export const DEFAULT_THEME: ThemeMode = "light";