type ClientNavigate = (to: string, options: { replace: boolean }) => void | Promise<void>;

interface SessionLifecycle {
  onStart?: () => void | Promise<void>;
  onEnd?: () => void;
}

let navigateFn: ClientNavigate | null = null;
let sessionLifecycle: SessionLifecycle = {};

export function registerClientNavigate(fn: ClientNavigate): void {
  navigateFn = fn;
}

export function registerSessionLifecycle(lifecycle: SessionLifecycle): void {
  sessionLifecycle = lifecycle;
}

export function resetClientNavigate(): void {
  navigateFn = null;
  sessionLifecycle = {};
}

export function notifySessionStart(): void {
  void sessionLifecycle.onStart?.();
}

export function notifySessionEnd(): void {
  sessionLifecycle.onEnd?.();
}

/**
 * Stay inside the already-loaded SPA when possible.
 * A full `location.replace` makes nginx look up a real file (e.g. `/auth/login`) and 404.
 */
export function clientReplace(to: string): void {
  if (!navigateFn) {
    window.location.replace(to);
    return;
  }

  void Promise.resolve(navigateFn(to, { replace: true })).catch(() => {
    window.location.replace(to);
  });
}