fix: front-end improvements

makes some fields visible and other hidden depending on the result of
some API calls, e.g. visitor is logged in -> show "Log out" button

WebApp/ts/eventList.ts

@@ -1,19 +1,26 @@
-var isAscending: boolean = false;
+import { getEvent, getMyAccount, unhideElementById } from './generalUseHelpers.js';
+
+var isAscending: boolean = false;
 
 function toggleListSortOrder() {
     isAscending = !isAscending;
     loadEvents();
 }
 
+async function getEvents() {
+    const res = await fetch("/api/events" + (isAscending ? "?sort=asc" : ""));
+    if (!res.ok) throw new Error("Błąd pobierania wydarzeń");
+
+    const events = await res.json();
+    return events;
+}
+
 async function loadEvents() {
     const container = document.getElementById("eventList");
     if (!container) return;
 
     try {
-        const res = await fetch("/api/events" + (isAscending ? "?sort=asc" : ""));
-        if (!res.ok) throw new Error("Błąd pobierania wydarzeń");
-
-        const events = await res.json();
+        var events = await getEvents();
 
         if (events.length === 0) {
             container.innerHTML = "<p class='text-muted'>Brak wydarzeń do wyświetlenia.</p>";
@@ -41,6 +48,20 @@ async function loadEvents() {
 }
 
 document.addEventListener("DOMContentLoaded", async () => {
+
+    var user = await getMyAccount();
+
+    if (user) {
+        if (user.isOrganisation) {
+            unhideElementById(document, "mainContainer");
+            unhideElementById(document, "addnewevent-btn");
+        }
+        unhideElementById(document, "logout-btn");
+    } else {
+        unhideElementById(document, "joinnow-btn");
+        unhideElementById(document, "signin-btn");
+    }
+
     loadEvents();
     // listen for clicks
     const listSortToggleButton = document.getElementById("list-sort-btn");