Navbar que se encoge

import { useEffect, useRef, useState } from "react";
import { motion } from "framer-motion";
import { Bell, Search } from "lucide-react";

const spring = { type: "spring" as const, stiffness: 300, damping: 30 };

interface ShrinkingNavbarProps {
  threshold?: number;
  /** true: caja de demo con scroll propio. false: navbar fijo arriba que escucha el scroll de la página. */
  contained?: boolean;
}

export default function ShrinkingNavbar({
  threshold = 18,
  contained = true,
}: ShrinkingNavbarProps) {
  const containerRef = useRef<HTMLDivElement>(null);
  const [small, setSmall] = useState(false);

  // Escucha el scroll del contenedor propio si existe; si no, el de la ventana.
  useEffect(() => {
    const el = contained ? containerRef.current : null;
    const read = () => setSmall((el ? el.scrollTop : window.scrollY) > threshold);
    const target: HTMLElement | Window = el ?? window;
    read();
    target.addEventListener("scroll", read, { passive: true });
    return () => target.removeEventListener("scroll", read);
  }, [contained, threshold]);

  const nav = (
    <motion.nav
      animate={{ maxWidth: small ? 250 : 340, height: small ? 44 : 58 }}
      transition={spring}
      style={{ width: "100%" }}
      className="sticky top-0 z-10 flex shrink-0 items-center justify-between rounded-full bg-white/70 dark:bg-black/70 px-5 shadow-[0_1px_2px_rgba(0,0,0,0.03),0_8px_28px_rgba(0,0,0,0.05)] backdrop-blur-[20px]"
    >
      <b>AIMRAN</b>
      <div className="flex gap-3">
        <Search className="h-4 w-4" />
        <Bell className="h-4 w-4" />
      </div>
    </motion.nav>
  );

  if (!contained) {
    return <div className="sticky top-0 z-50 flex justify-center p-4 text-[#1d1d1f] dark:text-[#f5f5f7]">{nav}</div>;
  }

  return (
    <div
      ref={containerRef}
      className="flex h-52 w-full flex-col items-center overflow-y-auto rounded-2xl bg-black/5 p-4 text-[#1d1d1f] dark:text-[#f5f5f7] dark:bg-white/10"
    >
      {nav}
      {/* Contenido de relleno para poder hacer scroll; también da 340 px de ancho natural sin forzar un mínimo */}
      <svg aria-hidden className="h-[326px] w-[340px] max-w-full shrink-0" />
    </div>
  );
}