type NavigationListener = (loading: boolean) => void;

let listeners = new Set<NavigationListener>();
let loading = false;

function notify() {
  listeners.forEach((listener) => listener(loading));
}

export function subscribeNavigationLoading(listener: NavigationListener) {
  listeners.add(listener);
  listener(loading);
  return () => {
    listeners.delete(listener);
  };
}

export function startNavigation() {
  if (loading) return;
  loading = true;
  notify();
}

export function stopNavigation() {
  if (!loading) return;
  loading = false;
  notify();
}

export function isNavigationLoading() {
  return loading;
}

export function isInternalNavigationClick(
  event: MouseEvent,
  anchor: HTMLAnchorElement
): boolean {
  if (event.defaultPrevented) return false;
  if (event.button !== 0) return false;
  if (event.metaKey || event.ctrlKey || event.shiftKey || event.altKey) return false;
  if (anchor.target === "_blank") return false;
  if (anchor.hasAttribute("download")) return false;

  const href = anchor.getAttribute("href");
  if (
    !href ||
    href.startsWith("#") ||
    href.startsWith("mailto:") ||
    href.startsWith("tel:") ||
    href.startsWith("javascript:")
  ) {
    return false;
  }

  try {
    const url = new URL(href, window.location.href);
    if (url.origin !== window.location.origin) return false;
    if (
      url.pathname === window.location.pathname &&
      url.search === window.location.search &&
      !url.hash
    ) {
      return false;
    }
    return true;
  } catch {
    return false;
  }
}