/** Profile links: what QR codes and invites contain, and how scans are read back. */

const USERNAME = /^[a-z0-9_]{3,32}$/;

/** Shareable profile URL on the website, e.g. https://musicshare.app/u/alice */
export function profileUrl(webBase: string, username: string): string {
  return `${webBase.replace(/\/+$/, '')}/u/${encodeURIComponent(username)}`;
}

/**
 * Pull a username out of anything a QR scan might contain: a website profile
 * URL (any host), the app's deep link (musicshare://u/alice), an Expo Go dev
 * link (exp://…/--/u/alice), or a bare "@alice". Returns null if it isn't one.
 */
export function parseProfileLink(text: string): string | null {
  const raw = text.trim();
  const at = raw.match(/^@([A-Za-z0-9_]+)$/);
  if (at) return valid(at[1]!);

  let url: URL;
  try {
    url = new URL(raw);
  } catch {
    return null;
  }
  // musicshare://u/alice parses with host "u" and path "/alice"
  const path = url.protocol === 'musicshare:' ? `/${url.host}${url.pathname}` : url.pathname.replace(/^\/--/, '');
  const match = path.match(/^\/u\/([^/?#]+)\/?$/);
  return match ? valid(decodeURIComponent(match[1]!)) : null;
}

function valid(name: string): string | null {
  const username = name.toLowerCase();
  return USERNAME.test(username) ? username : null;
}