implement changing username

flutter/lib/pages/account/account.dart

@@ -13,6 +13,7 @@ import 'package:simplecloudnotifier/state/application_log.dart';
 import 'package:simplecloudnotifier/state/globals.dart';
 import 'package:simplecloudnotifier/state/app_auth.dart';
 import 'package:simplecloudnotifier/types/immediate_future.dart';
+import 'package:simplecloudnotifier/utils/dialogs.dart';
 import 'package:simplecloudnotifier/utils/navi.dart';
 import 'package:simplecloudnotifier/utils/toaster.dart';
 import 'package:simplecloudnotifier/utils/ui.dart';
@@ -359,13 +360,15 @@ class _AccountRootPageState extends State<AccountRootPage> {
           mainAxisAlignment: MainAxisAlignment.start,
           children: [
             UI.buttonIconOnly(
-              onPressed: () {/*TODO*/},
+              onPressed: _changeUsername,
               icon: FontAwesomeIcons.pen,
             ),
             const SizedBox(height: 4),
             if (!user.isPro)
               UI.buttonIconOnly(
-                onPressed: () {/*TODO*/},
+                onPressed: () {
+                  Toaster.info("Not Implemented", "Account Upgrading will be implemented in a later version"); // TODO
+                },
                 icon: FontAwesomeIcons.cartCircleArrowUp,
               ),
           ],
@@ -502,4 +505,31 @@ class _AccountRootPageState extends State<AccountRootPage> {
   void _deleteAccount() async {
     //TODO
   }
+
+  void _changeUsername() async {
+    final acc = AppAuth();
+    if (!acc.isAuth()) return;
+
+    var newusername = await UIDialogs.showTextInput(context, 'Change your public username', 'Enter new username');
+    if (newusername == null) return;
+
+    newusername = newusername.trim();
+    if (newusername == '') {
+      Toaster.error("Error", 'Username cannot be empty');
+      return;
+    }
+
+    try {
+      final user = await APIClient.updateUser(acc, acc.userID!, username: newusername);
+      setState(() {
+        futureUser = ImmediateFuture.ofValue(user);
+      });
+      Toaster.success("Success", 'Username changed');
+
+      _backgroundRefresh();
+    } catch (exc, trace) {
+      Toaster.error("Error", 'Failed to update username');
+      ApplicationLog.error('Failed to update username: ' + exc.toString(), trace: trace);
+    }
+  }
 }