Fix fingerprint: adaptive auth screen (login/register by state), auto-prompt biometric on open, optimistic switch, real error messages

lib/auth_screen.dart

@@ -4,7 +4,7 @@ import 'package:login_vault_app/auth_service.dart';
 import 'package:login_vault_app/dashboard_screen.dart';
 import 'package:login_vault_app/theme_provider.dart';
 
-/// First screen: register, or (if registered) re-authenticate.
+/// First screen: register (if not yet), or re-authenticate (if registered).
 /// If a valid session exists, skip straight to the Dashboard.
 class AuthScreen extends StatefulWidget {
   final AuthService auth;
@@ -24,9 +24,39 @@ class _AuthScreenState extends State<AuthScreen> {
   @override
   void initState() {
     super.initState();
+    _initMode();
+  }
+
+  /// Decide login vs register based on whether an account exists.
+  Future<void> _initMode() async {
+    final registered = await widget.auth.isRegistered();
+    if (!mounted) return;
+    setState(() => _isLogin = registered);
+    // If already registered and biometric is enabled, prompt fingerprint
+    // automatically (unless a valid session already skips to dashboard).
+    if (registered && await widget.auth.isBiometricEnabled()) {
+      final timeout = await widget.auth.getTimeoutMinutes();
+      final valid = await widget.auth.hasValidSession(timeout);
+      if (!valid) {
+        _promptBiometricOnOpen();
+        return; // skip silent-auth path; biometric handles entry
+      }
+    }
     _trySilentAuth();
   }
 
+  /// Auto-prompt fingerprint on open when enabled; on success go to dashboard
+  /// (email may be empty for google-less accounts, fallback to stored email).
+  Future<void> _promptBiometricOnOpen() async {
+    final (ok, err) = await widget.auth.authenticateWithBiometrics();
+    if (!mounted) return;
+    if (ok) {
+      final email = await widget.auth.getEmail() ?? '';
+      _goToDashboard(email);
+    }
+    // on failure, the auth screen stays; user can tap Masuk manually
+  }
+
   /// On open: if a valid session is present, go straight to Dashboard.
   Future<void> _trySilentAuth() async {
     final timeout = await widget.auth.getTimeoutMinutes();
@@ -51,7 +81,7 @@ class _AuthScreenState extends State<AuthScreen> {
     );
   }
 
-  Future<void> _submitEmail() async {
+  Future<void> _submit() async {
     setState(() => _busy = true);
     final email = _emailCtrl.text.trim();
     final pass = _passCtrl.text;
@@ -113,20 +143,9 @@ class _AuthScreenState extends State<AuthScreen> {
             const SizedBox(height: 12),
             _busy
                 ? const CircularProgressIndicator()
-                : Column(
-                    children: [
-                      ElevatedButton(
-                        onPressed: _submitEmail,
-                        child: Text(_isLogin ? 'Masuk' : 'Daftar'),
-                      ),
-                      TextButton(
-                        onPressed: () =>
-                            setState(() => _isLogin = !_isLogin),
-                        child: Text(_isLogin
-                            ? 'Belum punya akun? Daftar'
-                            : 'Sudah punya akun? Masuk'),
-                      ),
-                    ],
+                : ElevatedButton(
+                    onPressed: _submit,
+                    child: Text(_isLogin ? 'Masuk' : 'Daftar'),
                   ),
           ],
         ),

lib/auth_service.dart

@@ -1,3 +1,6 @@
+import 'dart:io';
+import 'dart:async';
+import 'package:flutter/services.dart';
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import 'package:local_auth/local_auth.dart';
 import 'package:shared_preferences/shared_preferences.dart';
@@ -50,39 +53,41 @@ class AuthService {
     }
   }
 
-  /// Prompt the OS biometric dialog. Returns true on success.
-  /// [errorOut] receives a human-readable reason when it fails.
-  Future<bool> authenticateWithBiometrics({String? errorOut}) async {
-    try {
-      // Prefer strict biometric (fingerprint). If the device only has
-      // weaker biometrics (face) or none enrolled, fall back to allowing
-      // device credentials so the user isn't hard-blocked.
-      bool ok = false;
+  /// Prompt the OS biometric dialog.
+  /// Returns (success, errorMessage). errorMessage is null on success.
+  Future<(bool, String?)> authenticateWithBiometrics() async {
+    String? lastErr;
+    // Prefer strict biometric (fingerprint). If that fails, fall back to
+    // device credentials (PIN/pattern) so the user isn't hard-blocked.
+    for (final opt in [
+      const AuthenticationOptions(
+          biometricOnly: true, stickyAuth: true, sensitiveTransaction: true),
+      const AuthenticationOptions(
+          biometricOnly: false, stickyAuth: true, sensitiveTransaction: true),
+    ]) {
       try {
-        ok = await _localAuth.authenticate(
+        final ok = await _localAuth.authenticate(
           localizedReason: 'Gunakan biometrik untuk membuka Login Vault',
-          options: const AuthenticationOptions(
-            biometricOnly: true,
-            stickyAuth: true,
-          ),
+          options: opt,
         );
-      } catch (_) {
-        ok = false;
+        if (ok) return (true, null);
+      } on PlatformException catch (e) {
+        lastErr = '${e.code}: ${e.message}';
+        // user cancel / negative button -> stop retrying
+        if (e.code == 'PasscodeNotSet' ||
+            e.code == 'NotAvailable' ||
+            e.code == 'NotEnrolled' ||
+            e.code == 'LockedOut' ||
+            e.code == 'UserCancel' ||
+            e.code == 'Canceled' ||
+            e.code == 'UserFallback') {
+          return (false, lastErr);
+        }
+      } catch (e) {
+        lastErr = e.toString();
       }
-      if (!ok) {
-        ok = await _localAuth.authenticate(
-          localizedReason: 'Gunakan biometrik / kredensial perangkat',
-          options: const AuthenticationOptions(
-            biometricOnly: false,
-            stickyAuth: true,
-          ),
-        );
-      }
-      return ok;
-    } catch (e) {
-      if (errorOut != null) errorOut = e.toString();
-      return false;
     }
+    return (false, lastErr);
   }
 
   // ---------- Session ----------

lib/settings_screen.dart

@@ -19,6 +19,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
   final _oldCtrl = TextEditingController();
   final _newCtrl = TextEditingController();
   String? _msg;
+  Color _msgColor = Colors.green;
   bool _biometricOn = false;
   bool _biometricAvailable = false;
   int _timeout = 3;
@@ -48,35 +49,53 @@ class _SettingsScreenState extends State<SettingsScreen> {
     final oldP = _oldCtrl.text;
     final newP = _newCtrl.text;
     if (newP.isEmpty) {
-      setState(() => _msg = 'Password baru wajib diisi');
+      setState(() {
+        _msg = 'Password baru wajib diisi';
+        _msgColor = Colors.red;
+      });
       return;
     }
     final stored = await widget.auth.getAppPassword();
     if (stored != null && stored != '__google__' && stored != oldP) {
-      setState(() => _msg = 'Password lama salah');
+      setState(() {
+        _msg = 'Password lama salah';
+        _msgColor = Colors.red;
+      });
       return;
     }
     await widget.auth.changePassword(newP);
-    setState(() => _msg = 'Password aplikasi berhasil diubah');
+    setState(() {
+      _msg = 'Password aplikasi berhasil diubah';
+      _msgColor = Colors.green;
+    });
     _oldCtrl.clear();
     _newCtrl.clear();
   }
 
   Future<void> _toggleBiometric(bool value) async {
     if (value && !_biometricAvailable) {
-      setState(() => _msg = 'Perangkat tidak mendukung biometrik');
+      setState(() {
+        _msg = 'Perangkat tidak mendukung biometrik';
+        _msgColor = Colors.red;
+      });
       return;
     }
+    // optimistic: move switch immediately so it feels responsive
+    if (mounted) setState(() => _biometricOn = value);
     if (value) {
-      String? err;
-      final ok = await widget.auth.authenticateWithBiometrics(errorOut: err);
+      final (ok, err) = await widget.auth.authenticateWithBiometrics();
       if (!ok) {
-        setState(() => _msg = 'Verifikasi biometrik gagal: ${err ?? "dibatalkan"}');
+        if (mounted) {
+          setState(() {
+            _biometricOn = false;
+            _msg = 'Verifikasi biometrik gagal: ${err ?? "dibatalkan"}';
+            _msgColor = Colors.red;
+          });
+        }
         return;
       }
     }
     await widget.auth.setBiometricEnabled(value);
-    if (mounted) setState(() => _biometricOn = value);
   }
 
   Future<void> _setTimeout(int? value) async {
@@ -121,12 +140,19 @@ class _SettingsScreenState extends State<SettingsScreen> {
           ListTile(
             title: const Text('Timeout (tanpa aktivitas)'),
             subtitle: Text('Logout otomatis setelah: ${_timeoutLabel(_timeout)}'),
-            trailing: DropdownButton<int>(
-              value: _timeout,
-              items: _timeoutOptions
-                  .map((m) => DropdownMenuItem(value: m, child: Text(_timeoutLabel(m))))
+            trailing: PopupMenuButton<int>(
+              initialValue: _timeoutOptions.contains(_timeout) ? _timeout : _timeoutOptions.first,
+              onSelected: _setTimeout,
+              itemBuilder: (ctx) => _timeoutOptions
+                  .map((m) => PopupMenuItem(value: m, child: Text(_timeoutLabel(m))))
                   .toList(),
-              onChanged: _setTimeout,
+              child: Row(
+                mainAxisSize: MainAxisSize.min,
+                children: [
+                  Text(_timeoutLabel(_timeout)),
+                  const Icon(Icons.arrow_drop_down),
+                ],
+              ),
             ),
           ),
           SwitchListTile(
@@ -158,7 +184,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
           if (_msg != null)
             Padding(
               padding: const EdgeInsets.only(top: 8),
-              child: Text(_msg!, style: const TextStyle(color: Colors.green)),
+              child: Text(_msg!, style: TextStyle(color: _msgColor)),
             ),
           const Divider(),
           ListTile(