Frontend first draft

frontend/pweb/lib/widgets/username.dart

@@ -0,0 +1,43 @@
+import 'package:flutter/material.dart';
+
+import 'package:pweb/generated/i18n/app_localizations.dart';
+
+
+class UsernameField extends StatelessWidget {
+  final TextEditingController controller;
+  final ValueChanged<bool>? onValid;
+
+  const UsernameField({
+    super.key,
+    required this.controller,
+    this.onValid,
+  });
+
+  String? _reportResult(String? msg) {
+    onValid?.call(msg == null);
+    return msg;
+  }
+
+  @override
+  Widget build(BuildContext context) => TextFormField(
+    controller: controller,
+    decoration: InputDecoration(
+      labelText: AppLocalizations.of(context)!.username,
+      hintText: AppLocalizations.of(context)!.usernameHint,
+    ),
+    validator: (value) {
+      return _reportResult((value?.isNotEmpty ?? false) ? null : AppLocalizations.of(context)!.usernameErrorInvalid);
+      // bool isValid = value != null && EmailValidator.validate(value);
+      // if (!isValid) {
+      //   return _reportResult(AppLocalizations.of(context)!.usernameErrorInvalid);
+      // }
+      // final tld = value.split('.').last;
+      // isValid = tlds.contains(tld);
+      // if (!isValid) {
+      //   return _reportResult(AppLocalizations.of(context)!.usernameUnknownTLD(tld));
+      // }
+      // return _reportResult(null);
+    },
+    onChanged: (value) => onValid?.call(value.isNotEmpty),
+  );
+}