(() => {
  let container;

  function ensureContainer() {
    if (!container) {
      container = document.createElement("div");
      container.className = "toast-container";
      document.body.appendChild(container);
    }
    return container;
  }

  function show({ message, level = "info", timeout = 5000 } = {}) {
    const root = ensureContainer();
    const toast = document.createElement("div");
    toast.className = `toast toast--${level}`;
    toast.setAttribute("role", "alert");
    toast.innerHTML = `
      <span class="toast__icon" aria-hidden="true"></span>
      <p class="toast__message">${message}</p>
      <button type="button" class="toast__close" aria-label="Dismiss">×</button>
    `;
    root.appendChild(toast);

    const close = () => {
      toast.classList.add("hidden");
      setTimeout(() => toast.remove(), 200);
    };

    toast.querySelector(".toast__close").addEventListener("click", close);

    if (timeout > 0) {
      setTimeout(close, timeout);
    }
  }

  window.NotificationCenter = { show };
})();