Add generateInviteLink util function

frontend/src/lib/utils.ts

@@ -1,6 +1,6 @@
 import { clsx, type ClassValue } from "clsx";
 import { twMerge } from "tailwind-merge";
-import { BACKEND_API_URL } from "@/lib/constants";
+import { APP_URL, BACKEND_API_URL } from "@/lib/constants";
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));
@@ -70,3 +70,18 @@ export function formatTime(
 export const getServerFileUrl = (url?: string | null) => {
   return url ? `${BACKEND_API_URL}/files/${url}` : undefined;
 };
+
+export const generateInviteLink = (
+  eventSlug: string,
+  invitationCode: string,
+): string => {
+  const baseUrl = APP_URL;
+
+  if (!baseUrl) {
+    console.warn("NEXT_PUBLIC_APP_URL is not defined in environment variables");
+    // Fallback for development
+    return `/invite/${eventSlug}?code=${invitationCode}`;
+  }
+
+  return `${baseUrl}/invite/${eventSlug}?code=${invitationCode}`;
+};