Errores

{
  "error": {
    "type": "invalid_request_error",
    "code": "missing_field",
    "message": "El campo 'link_id' es requerido.",
    "param": "link_id",
    "doc_url": "https://docs.rail.cl/guides/errors#missing_field"
  }
}

async function railFetch<T>(path: string, opts: RequestInit): Promise<T> {
  const res = await fetch(`https://api.rail.cl${path}`, opts);
  if (!res.ok) {
    const body = await res.json().catch(() => ({}));
    const err = body.error ?? {};
    throw new RailError(res.status, err.code, err.message, err.param);
  }
  return res.json();
}

class RailError extends Error {
  constructor(
    public status: number,
    public code: string,
    message: string,
    public param?: string,
  ) {
    super(message);
  }
}

try {
  await railFetch('/v1/refresh_intents', { ... });
} catch (e) {
  if (e instanceof RailError) {
    if (e.code === 'refresh_intent_in_progress') {
      // No es error real — ya está corriendo
      return;
    }
    if (e.code === 'rejected_credentials') {
      // Notificá al user para que re-conecte
    }
    if (e.status >= 500) {
      // Transient, reintentar con backoff
    }
  }
}