fix(buy,sell): correct how the amount field handles grouped and rejected input

assets/languages/strings_de.arb

@@ -111,6 +111,8 @@
   "identityCheckProcessDescription": "Als nächstes müssen Sie Ihre Identität verifizieren. Bitte halten Sie Ihren Ausweis bereit und erlauben Sie den Kamerazugriff auf dem Gerät.",
   "identityCheckRequired": "Identitätsprüfung erforderlich",
   "imprint": "Impressum",
+  "invalidAmountFormatDescription": "Bitte geben Sie den Betrag zum Beispiel als 1000 oder 1000,50 ein.",
+  "invalidAmountFormatTitle": "Betrag nicht lesbar",
   "kyc": "Eröffnungsprozess",
   "kycAccountMergeDescription": "Ihre Identität wurde bereits in einem anderen Konto gefunden. Eine Zusammenführungsanfrage wurde erstellt. Bitte bestätigen Sie diese über die E-Mail, die Sie erhalten haben.",
   "kycAccountMergeTitle": "Kontozusammenführung erforderlich",
@@ -465,4 +467,4 @@
   "youPay": "Sie bezahlen",
   "youReceive": "Sie erhalten",
   "youSell": "Sie verkaufen"
-}
+}

assets/languages/strings_en.arb

@@ -111,6 +111,8 @@
   "identityCheckProcessDescription": "Next, you need to verify your identity. Please have your ID ready and allow camera access on your device.",
   "identityCheckRequired": "Identity check required",
   "imprint": "Imprint",
+  "invalidAmountFormatDescription": "Please enter the amount as 1000 or 1000.50, for example.",
+  "invalidAmountFormatTitle": "Amount is not readable",
   "kyc": "Onboarding process",
   "kycAccountMergeDescription": "Your identity was found in another account. A merge request has been created. Please confirm it via the email you received.",
   "kycAccountMergeTitle": "Account merge required",
@@ -465,4 +467,4 @@
   "youPay": "You pay",
   "youReceive": "You receive",
   "youSell": "You sell"
-}
+}

lib/packages/service/dfx/models/payment/payment_info_error.dart

@@ -7,4 +7,5 @@ enum PaymentInfoError {
   bitboxDisconnected,
   priceSourceUnavailable,
   unknown,
+  invalidAmountFormat,
 }

lib/packages/utils/fiat_amount.dart

@@ -7,6 +7,44 @@ double? tryParseFiatAmount(String input) {
   return double.tryParse(input.replaceAll(',', '.'));
 }
 
+/// Consecutive groups of three digits with the same separator.
+final _sameGrouping = RegExp(r'^(\d+)([.,])(\d{3}(?:\2\d{3})*)$');
+
+/// Thousands groups plus 1–2 digits of the other separator.
+final _mixedGrouping = RegExp(r'^(\d+)([.,])(\d{3}(?:\2\d{3})*)([.,])(\d{1,2})$');
+
+/// Grouping separator to drop from [input], or null if [input] is unchanged.
+String? _groupingSeparatorToStrip(String input) {
+  final same = _sameGrouping.firstMatch(input);
+  if (same != null) return same[2]!;
+  final mixed = _mixedGrouping.firstMatch(input);
+  if (mixed != null && mixed[2] != mixed[4]) return mixed[2]!;
+  return null;
+}
+
+/// Strips thousands grouping (`1.000` / `1,000` / `1.000.000` → integer).
+///
+/// EUR and CHF have two decimal places, so a separator followed by exactly
+/// three digits cannot be a decimal. Consecutive groups with the same
+/// separator are unambiguous thousands grouping, so a paste of `1.000.000`
+/// matches what typing the same characters one by one already produced.
+/// Mixed thousands + 1–2 decimal digits of the other separator (`1.000,50` /
+/// `1,000.50`) drop the thousands separator and keep the decimal, so paste
+/// matches typing. Real decimals (`300,75`) and partials (`1.`, `1.0`,
+/// `1.00`) are returned unchanged, as is mixed input that is not uniquely
+/// thousands-then-decimal (`1.000,000`, `3,5,7`).
+String normalizeFiatInput(String input) {
+  final separator = _groupingSeparatorToStrip(input);
+  if (separator == null) return input;
+  return input.replaceAll(separator, '');
+}
+
+/// The grouping separator [normalizeFiatInput] strips from [input], or null
+/// if [input] is left unchanged.
+String? strippedFiatGroupingSeparator(String input) {
+  return _groupingSeparatorToStrip(input);
+}
+
 /// The whole-currency integer the backend charges for the raw [input] the user
 /// typed (e.g. `300,75` → `301`); empty input counts as zero.
 int chargedFiatAmount(String input) {

lib/screens/buy/buy_page.dart

@@ -58,7 +58,15 @@ class _BuyViewState extends State<BuyView> {
         listener: (context, state) {
           _syncController(_amountController, state.fiatText);
           _syncController(_resultController, state.sharesText);
-          context.read<BuyPaymentInfoCubit>().getPaymentInfo(
+          final paymentInfo = context.read<BuyPaymentInfoCubit>();
+          // An empty field is not an amount to quote. Fetching it would
+          // charge 0 and, while that request is in flight, leave a previous
+          // Success (and its confirm button) on screen.
+          if (_amountController.text.isEmpty) {
+            paymentInfo.clearQuote();
+            return;
+          }
+          paymentInfo.getPaymentInfo(
             amount: _amountController.text,
             currency: state.currency,
           );

lib/screens/buy/cubits/buy_converter/buy_converter_cubit.dart

@@ -48,7 +48,7 @@ class BuyConverterCubit extends Cubit<BuyConverterState> {
       } catch (e) {
         developer.log(e.toString());
         if (isClosed || mySeq != _seq) return;
-        emit(state.copyWith(loading: false));
+        emit(state.copyWith(loading: false, sharesText: ''));
       }
     });
   }
@@ -75,7 +75,7 @@ class BuyConverterCubit extends Cubit<BuyConverterState> {
       } catch (e) {
         developer.log(e.toString());
         if (isClosed || mySeq != _seq) return;
-        emit(state.copyWith(loading: false));
+        emit(state.copyWith(loading: false, fiatText: ''));
       }
     });
   }
@@ -99,7 +99,7 @@ class BuyConverterCubit extends Cubit<BuyConverterState> {
     } catch (e) {
       developer.log(e.toString());
       if (isClosed || mySeq != _seq) return;
-      emit(state.copyWith(loading: false));
+      emit(state.copyWith(loading: false, sharesText: ''));
     }
   }
 

lib/screens/buy/cubits/buy_payment_info/buy_payment_info_cubit.dart

@@ -58,10 +58,26 @@ class BuyPaymentInfoCubit extends Cubit<BuyPaymentInfoState> {
     emit(newState);
   }
 
+  /// Drops a landed quote so it cannot be confirmed after the amount it
+  /// belonged to has disappeared. Cancels an in-flight fetch to keep a
+  /// later completion from restoring the old Success.
+  void clearQuote() {
+    _completer?.cancel();
+    if (isClosed) return;
+    emit(const BuyPaymentInfoInitial());
+  }
+
   Future<BuyPaymentInfoState> _runGetPaymentInfo(String amount, Currency currency) async {
+    final int charged;
+    try {
+      charged = chargedFiatAmount(amount);
+    } on FormatException {
+      return const BuyPaymentInfoFailure(PaymentInfoError.invalidAmountFormat);
+    }
+
     try {
       final paymentInfo = await _buyPaymentInfoService.getPaymentInfo(
-        chargedFiatAmount(amount),
+        charged,
         currency: currency,
       );
 

lib/screens/buy/widgets/payment_converter.dart

@@ -11,6 +11,7 @@ import 'package:realunit_wallet/screens/buy/cubits/buy_converter/buy_converter_c
 import 'package:realunit_wallet/setup/di.dart';
 import 'package:realunit_wallet/styles/colors.dart';
 import 'package:realunit_wallet/styles/currency.dart';
+import 'package:realunit_wallet/widgets/fiat_input_formatter.dart';
 
 class PaymentConverter extends StatefulWidget {
   const PaymentConverter({
@@ -100,7 +101,7 @@ class _PaymentConverterState extends State<PaymentConverter> {
                   child: TextField(
                     controller: _amountController,
                     keyboardType: const .numberWithOptions(decimal: true),
-                    inputFormatters: [FilteringTextInputFormatter.allow(RegExp(r'[0-9.,]'))],
+                    inputFormatters: const [FiatInputFormatter()],
                     decoration: const InputDecoration(
                       border: .none,
                       contentPadding: .symmetric(

lib/screens/buy/widgets/payment_information.dart

@@ -37,6 +37,11 @@ class PaymentInformation extends StatelessWidget {
               title: S.of(context).bitboxDisconnectedTitle,
               description: S.of(context).bitboxDisconnectedDescription,
             );
+          } else if (error == PaymentInfoError.invalidAmountFormat) {
+            return PaymentActionRequired(
+              title: S.of(context).invalidAmountFormatTitle,
+              description: S.of(context).invalidAmountFormatDescription,
+            );
           } else if (error == PaymentInfoError.priceSourceUnavailable ||
               error == PaymentInfoError.unknown) {
             if (paymentInfoState.message.isEmpty) {

lib/screens/sell/cubits/sell_converter/sell_converter_cubit.dart

@@ -48,7 +48,7 @@ class SellConverterCubit extends Cubit<SellConverterState> {
       } catch (e) {
         developer.log(e.toString());
         if (isClosed || mySeq != _seq) return;
-        emit(state.copyWith(loading: false));
+        emit(state.copyWith(loading: false, sharesText: ''));
       }
     });
   }
@@ -75,7 +75,7 @@ class SellConverterCubit extends Cubit<SellConverterState> {
       } catch (e) {
         developer.log(e.toString());
         if (isClosed || mySeq != _seq) return;
-        emit(state.copyWith(loading: false));
+        emit(state.copyWith(loading: false, fiatText: ''));
       }
     });
   }
@@ -99,7 +99,7 @@ class SellConverterCubit extends Cubit<SellConverterState> {
     } catch (e) {
       developer.log(e.toString());
       if (isClosed || mySeq != _seq) return;
-      emit(state.copyWith(loading: false));
+      emit(state.copyWith(loading: false, fiatText: ''));
     }
   }
 

lib/screens/sell/widgets/sell_converter.dart

@@ -14,6 +14,7 @@ import 'package:realunit_wallet/screens/sell/widgets/sell_max_amount_button.dart
 import 'package:realunit_wallet/setup/di.dart';
 import 'package:realunit_wallet/styles/colors.dart';
 import 'package:realunit_wallet/styles/currency.dart';
+import 'package:realunit_wallet/widgets/fiat_input_formatter.dart';
 
 class SellConverter extends StatefulWidget {
   const SellConverter({
@@ -222,7 +223,7 @@ class _SellConverterState extends State<SellConverter> {
                   child: TextField(
                     controller: _resultController,
                     keyboardType: const TextInputType.numberWithOptions(decimal: true),
-                    inputFormatters: [FilteringTextInputFormatter.allow(RegExp(r'[0-9.,]'))],
+                    inputFormatters: const [FiatInputFormatter()],
                     decoration: const InputDecoration(
                       border: InputBorder.none,
                       contentPadding: EdgeInsets.symmetric(

lib/widgets/fiat_input_formatter.dart

@@ -0,0 +1,36 @@
+import 'package:flutter/services.dart';
+import 'package:realunit_wallet/packages/utils/fiat_amount.dart';
+
+/// Digits and separators only. A completed thousands group (`1.000` /
+/// `1,000` / `1.000.000`) is rewritten to the integer; mixed thousands plus
+/// decimal (`1.000,50` / `1,000.50`) keep the decimal; partials (`1.`,
+/// `1.0`, `1.00`) stay as typed.
+class FiatInputFormatter extends TextInputFormatter {
+  const FiatInputFormatter();
+
+  static final _allowedChars = FilteringTextInputFormatter.allow(RegExp(r'[0-9.,]'));
+
+  @override
+  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
+    final allowed = _allowedChars.formatEditUpdate(oldValue, newValue);
+    final separator = strippedFiatGroupingSeparator(allowed.text);
+    final normalized = normalizeFiatInput(allowed.text);
+    if (normalized == allowed.text) return allowed;
+    final cursor = allowed.selection.baseOffset.clamp(0, allowed.text.length);
+    // Only separators actually dropped that sit before the caret. A global
+    // length delta also subtracts separators behind it (typing `1` into
+    // `.000,50` would move the caret to 0 instead of 1).
+    var removedBefore = 0;
+    if (separator != null) {
+      for (var i = 0; i < cursor; i++) {
+        if (allowed.text[i] == separator) removedBefore++;
+      }
+    }
+    return TextEditingValue(
+      text: normalized,
+      selection: TextSelection.collapsed(
+        offset: (cursor - removedBefore).clamp(0, normalized.length),
+      ),
+    );
+  }
+}

test/goldens/screens/buy/buy_golden_test.dart

@@ -270,6 +270,31 @@ void main() {
       },
     );
 
+    goldenTest(
+      'invalid amount format failure',
+      fileName: 'buy_invalid_amount_format',
+      constraints: const BoxConstraints.tightFor(width: 390, height: 844),
+      builder: () {
+        when(() => paymentInfoCubit.state).thenReturn(
+          const BuyPaymentInfoFailure(PaymentInfoError.invalidAmountFormat),
+        );
+        when(() => converterCubit.state).thenReturn(
+          const BuyConverterState(
+            // This golden stubs the failure panel and does not run the
+            // formatter. Same-separator thousands groups and mixed
+            // thousands + 1–2 decimal digits of the other separator are
+            // stripped before the parser; a 3-digit mixed tail is not a
+            // unique thousands-then-decimal, so `1.000,000` is left as
+            // typed, reaches chargedFiatAmount, and throws FormatException.
+            fiatText: '1.000,000',
+            sharesText: '',
+            currency: Currency.chf,
+          ),
+        );
+        return wrapForGolden(buildSubject());
+      },
+    );
+
     goldenTest(
       'price source unavailable failure shows API message',
       fileName: 'buy_price_source_unavailable',

test/packages/service/dfx/models/payment/buy_sell_dtos_test.dart

@@ -182,9 +182,9 @@ void main() {
   });
 
   group('$PaymentInfoError', () {
-    test('has the eight documented variants', () {
+    test('has the nine documented variants', () {
       // Pin the wire contract — any new variant has to be added intentionally.
-      expect(PaymentInfoError.values, hasLength(8));
+      expect(PaymentInfoError.values, hasLength(9));
       expect(
         PaymentInfoError.values.toSet(),
         {
@@ -196,6 +196,7 @@ void main() {
           PaymentInfoError.bitboxDisconnected,
           PaymentInfoError.priceSourceUnavailable,
           PaymentInfoError.unknown,
+          PaymentInfoError.invalidAmountFormat,
         },
       );
     });

test/packages/utils/fiat_amount_test.dart

@@ -47,6 +47,10 @@ void main() {
 
     test('returns null on multi-separator input', () {
       expect(tryParseFiatAmount('1.300,75'), isNull);
+      // Consecutive thousands groups are stripped by [normalizeFiatInput]
+      // before the parser sees them. The parser itself still rejects the
+      // raw grouped form.
+      expect(tryParseFiatAmount('1.000.000'), isNull);
     });
 
     test('returns null on grouping-ambiguous input (separator + 3 digits)', () {
@@ -59,4 +63,47 @@ void main() {
       expect(tryParseFiatAmount('1,50'), 1.5);
     });
   });
+
+  group('normalizeFiatInput', () {
+    test('strips a lone thousands group', () {
+      expect(normalizeFiatInput('1.000'), '1000');
+      expect(normalizeFiatInput('1,000'), '1000');
+      expect(normalizeFiatInput('10.000'), '10000');
+      expect(normalizeFiatInput('10,000'), '10000');
+    });
+
+    test('strips consecutive thousands groups with the same separator', () {
+      expect(normalizeFiatInput('1.000.000'), '1000000');
+      expect(normalizeFiatInput('1,000,000'), '1000000');
+      expect(normalizeFiatInput('10.000.000'), '10000000');
+      expect(normalizeFiatInput('1000.000.000'), '1000000000');
+    });
+
+    test('strips mixed thousands grouping plus a decimal of the other separator', () {
+      expect(normalizeFiatInput('1.000,50'), '1000,50');
+      expect(normalizeFiatInput('1,000.50'), '1000.50');
+      expect(normalizeFiatInput('1.000,5'), '1000,5');
+      expect(normalizeFiatInput('1,000.5'), '1000.5');
+      expect(normalizeFiatInput('1.300,75'), '1300,75');
+      expect(normalizeFiatInput('1.000.000,50'), '1000000,50');
+      expect(normalizeFiatInput('1,000,000.50'), '1000000.50');
+    });
+
+    test('leaves every other input unchanged', () {
+      expect(normalizeFiatInput('300'), '300');
+      expect(normalizeFiatInput('300,75'), '300,75');
+      expect(normalizeFiatInput('0,5'), '0,5');
+      expect(normalizeFiatInput('1.000,000'), '1.000,000');
+      expect(normalizeFiatInput('1,000.000'), '1,000.000');
+      expect(normalizeFiatInput('1.000.50'), '1.000.50');
+      expect(normalizeFiatInput('1,000,50'), '1,000,50');
+      expect(normalizeFiatInput('3,5,7'), '3,5,7');
+    });
+
+    test('leaves partial thousands-group input unchanged', () {
+      expect(normalizeFiatInput('1.'), '1.');
+      expect(normalizeFiatInput('1.0'), '1.0');
+      expect(normalizeFiatInput('1.00'), '1.00');
+    });
+  });
 }