How do I use route guards?

// src/app/guards.ts
export const Guards = {
  requireAuth: (redirectTo: string = '/login'): Nutin.RouteGuard => {
    return () => {
      const isAuthenticated = !!localStorage.getItem('user_token');
      return isAuthenticated || redirectTo;
    };
  },
};

export const appRoutes: Nutin.Routes = {
  '/admin': { view: () => new AdminView(), guards: [Guards.requireAuth()] },
};

// Nutin.RouteGuard
type RouteGuard = (params: Record<string, string>) => boolean | string | Promise<boolean | string>;

Guards receive the matched route params (not the raw path or query string), and run in array order, stopping at the first non-true result:

• true — allow; the next guard runs, or the view renders if this was the last one.
• false — block the navigation entirely; the router stays on the current route (no re-render, no history change, no redirect).
• a string — treated as a redirect path; the router navigates there instead, and that target's own guards are evaluated too (a redirect can chain through further guards). During back/forward, reload() or the first load, the redirect replaces the guarded history entry instead of adding one.

Guards can be async/return a Promise — the router awaits the result before deciding.

With generateSEOFiles, guards also run during prerendering, as for an anonymous first visit (empty localStorage). A route a guard blocks or redirects isn't prerendered and is left out of the sitemap; the build logs it.

There's no core-level convention for where guards live — src/app/guards.ts (as above) is a common location, but any module works as long as it's imported by routes.ts.