fix: login field

lib/presentation/pages/auth/login/widgets/phone_field.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 
 import '../../../../../application/auth/check_phone_form/check_phone_form_bloc.dart';
@@ -36,6 +37,9 @@ class _LoginPhoneFieldState extends State<LoginPhoneField> {
 
   void _clearText() {
     _controller.clear();
+    context.read<CheckPhoneFormBloc>().add(
+      const CheckPhoneFormEvent.phoneNumberChanged(''),
+    );
     setState(() {});
   }
 
@@ -44,13 +48,19 @@ class _LoginPhoneFieldState extends State<LoginPhoneField> {
     return AppTextFormField(
       title: 'Masukkan no telepon',
       hintText: '8712671212',
+      helperText: 'Harus diawali angka 8',
       controller: _controller,
       focusNode: _focusNode,
       keyboardType: TextInputType.phone,
+      inputFormatters: [_PhoneAfterCountryCodeFormatter()],
       validator: (value) {
-        if (context.read<CheckPhoneFormBloc>().state.phoneNumber.isEmpty) {
+        final phoneNumber = context.read<CheckPhoneFormBloc>().state.phoneNumber;
+        if (phoneNumber.isEmpty) {
           return 'Masukkan no telepon';
         }
+        if (!phoneNumber.startsWith('8')) {
+          return 'No telepon harus diawali angka 8';
+        }
 
         return null;
       },
@@ -80,3 +90,27 @@ class _LoginPhoneFieldState extends State<LoginPhoneField> {
     );
   }
 }
+
+/// Prefix +62 sudah tampil di field, jadi input harus langsung diawali 8.
+/// Ketikan `0`/`6` di awal ditolak; tempelan `08…`, `62…`, atau `+62…`
+/// dirapikan jadi `8…`.
+class _PhoneAfterCountryCodeFormatter extends TextInputFormatter {
+  @override
+  TextEditingValue formatEditUpdate(
+    TextEditingValue oldValue,
+    TextEditingValue newValue,
+  ) {
+    var digits = newValue.text.replaceAll(RegExp(r'\D'), '');
+    if (digits.startsWith('62')) digits = digits.substring(2);
+    digits = digits.replaceFirst(RegExp(r'^0+'), '');
+
+    if (digits.isEmpty) return const TextEditingValue();
+    if (!digits.startsWith('8')) return oldValue;
+    if (digits == newValue.text) return newValue;
+
+    return TextEditingValue(
+      text: digits,
+      selection: TextSelection.collapsed(offset: digits.length),
+    );
+  }
+}