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/eventModify.ts

@@ -0,0 +1,99 @@
+import { getEvent, getMyAccount, unhideElementById } from './generalUseHelpers.js';
+
+const queryString = window.location.search;
+const urlParams = new URLSearchParams(queryString);
+const eventId = urlParams.get('event');
+
+async function modifyEvent()
+{
+    // Pobieranie danych z formularza
+    const title = (document.getElementById('title') as HTMLInputElement).value;
+    const location = (document.getElementById('location') as HTMLInputElement).value;
+    const description = (document.getElementById('description') as HTMLTextAreaElement).value;
+    const eventDateRaw = (document.getElementById('eventDate') as HTMLInputElement).value;
+
+    // Walidacja prostych pól
+    if (!title || !location || !eventDateRaw)
+    {
+        alert("Należy uzupełnić wszystkie pola!");
+        return;
+    }
+
+    const eventDate = new Date(eventDateRaw).toISOString();
+
+    const payload = {
+        title,
+        location,
+        description,
+        eventDate,
+    };
+
+    try
+    {
+        const response = await fetch('/api/events/' + eventId, {
+        method: 'PUT',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify(payload)
+        });
+
+        if (!response.ok)
+        {
+            const errorText = await response.text();
+            throw new Error(errorText);
+        }
+
+        alert("Wydarzenie zmodyfikowane!");
+        window.location.href = "/"; // Przekierowanie do strony głównej
+    } catch (error) {
+       console.error("Błąd podczas modyfikowania:", error);
+       alert("Nie udało się zmodyfikować wydarzenia: " + error);
+    }
+}
+
+document.addEventListener("DOMContentLoaded", async () => {
+    var container = document.getElementById("mainContainer");
+    const saveBtn = document.getElementById("saveBtn");
+    var user = await getMyAccount();
+    if (user) {
+        if (user.isOrganisation) {
+            unhideElementById(document, "mainContainer");
+        }
+        unhideElementById(document, "logout-btn");
+    } else {
+        unhideElementById(document, "joinnow-btn");
+        unhideElementById(document, "signin-btn");
+    }
+
+    if (saveBtn)
+    {
+        saveBtn.addEventListener("click", (e) => {
+            e.preventDefault();
+            createEvent();
+        });
+    }
+    if (eventId !== null && container !== null) {
+
+        try {
+            const titleInput       = document.getElementById(      'title') as HTMLInputElement;
+            const locationInput    = document.getElementById(   'location') as HTMLInputElement;
+            const descriptionInput = document.getElementById('description') as HTMLInputElement;
+            const dateInput        = document.getElementById(  'eventDate') as HTMLInputElement;
+            var ev = await getEvent(eventId);
+
+            if (ev === null) {
+                container.innerHTML = "<p class='text-muted'>Brak wydarzeń do wyświetlenia.</p>";
+                return;
+            } else {
+                      titleInput.value = ev.title                  || '';
+                   locationInput.value = ev.location               || '';
+                descriptionInput.value = ev.description            || '';
+                       dateInput.value = ev.eventDate.slice(0, 16) || '';
+            }
+
+        } catch (err) {
+            console.log(err);
+            container.innerHTML = `<p class="text-danger">` + err + `</p>`;
+        }
+        
+    }
+});