/**
 * Theme utilities — read / write the dark-mode preference and
 * apply it to <html>.
 *
 * Dark mode is a class-based Tailwind strategy (see
 * tailwind.config.js). The class is toggled on `<html>` and the
 * CSS in `app/globals.css` does the heavy lifting via the
 * `.dark { --surface-XXX }` overrides.
 *
 * The settings live in the same `1driver_settings` localStorage
 * key as the rest of AppSettings — see `lib/pocketbase.ts:231`
 * for the writer. We don't import the pocketbase module here so
 * that `applyDarkMode` can run during the pre-hydration
 * `import` phase in `app/layout.tsx` without dragging PB into
 * a server-only context.
 */

const SETTINGS_KEY = '1driver_settings';

function readSettings(): { darkMode?: boolean } {
  if (typeof window === 'undefined') return {};
  try {
    const raw = window.localStorage.getItem(SETTINGS_KEY);
    if (!raw) return {};
    return JSON.parse(raw) as { darkMode?: boolean };
  } catch {
    return {};
  }
}

/** Apply the persisted dark-mode preference to <html>. */
export function applyDarkMode(): void {
  if (typeof document === 'undefined') return;
  const { darkMode } = readSettings();
  document.documentElement.classList.toggle('dark', Boolean(darkMode));
}

/** Toggle the preference, persist it, and apply it. */
export function setDarkMode(enabled: boolean): void {
  if (typeof document === 'undefined') return;
  document.documentElement.classList.toggle('dark', enabled);

  // Persist alongside the rest of AppSettings — merge with whatever
  // is already there so we don't blow away locationInterval etc.
  let current: Record<string, unknown> = {};
  try {
    const raw = window.localStorage.getItem(SETTINGS_KEY);
    if (raw) current = JSON.parse(raw);
  } catch {
    /* corrupted JSON — start fresh */
  }
  current.darkMode = enabled;
  window.localStorage.setItem(SETTINGS_KEY, JSON.stringify(current));
}