const KEY = "fieldbook-theme";

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

export function readTheme(): Theme {
  try {
    const stored = localStorage.getItem(KEY);
    if (stored === "light" || stored === "dark") return stored;
    if (window.matchMedia("(prefers-color-scheme: dark)").matches) return "dark";
  } catch {
    /* ignore */
  }
  return "light";
}

export function applyTheme(theme: Theme) {
  document.documentElement.dataset.theme = theme;
  try {
    localStorage.setItem(KEY, theme);
  } catch {
    /* ignore */
  }
}

export function toggleTheme(): Theme {
  const next: Theme = readTheme() === "dark" ? "light" : "dark";
  applyTheme(next);
  return next;
}