refactor(autoswap): sanitize user-facing error messages

lib/core/errors/autoswap_errors.dart

@@ -1,58 +1,4 @@
 import 'package:bb_mobile/core/errors/bull_exception.dart';
-import 'package:bb_mobile/core/settings/domain/settings_entity.dart';
-import 'package:bb_mobile/core/utils/amount_conversions.dart';
-import 'package:bb_mobile/generated/l10n/localization.dart';
-
-class MinimumAmountThresholdException extends BullException {
-  final int minimumThresholdSats;
-  final BitcoinUnit bitcoinUnit;
-
-  MinimumAmountThresholdException(this.minimumThresholdSats, this.bitcoinUnit)
-    : super(
-        'Minimum balance threshold is $minimumThresholdSats ${bitcoinUnit.code}',
-      );
-
-  String displayMessage([AppLocalizations? loc]) {
-    if (loc == null) {
-      if (bitcoinUnit == BitcoinUnit.btc) {
-        final btcAmount = ConvertAmount.satsToBtc(minimumThresholdSats);
-        return 'Minimum balance threshold is $btcAmount BTC';
-      }
-      return 'Minimum balance threshold is $minimumThresholdSats sats';
-    }
-
-    if (bitcoinUnit == BitcoinUnit.btc) {
-      final btcAmount = ConvertAmount.satsToBtc(minimumThresholdSats);
-      return loc.autoswapMinimumThresholdErrorBtc(btcAmount.toString());
-    }
-    return loc.autoswapMinimumThresholdErrorSats(
-      minimumThresholdSats.toString(),
-    );
-  }
-}
-
-class MaximumFeeThresholdException extends BullException {
-  final int maximumThreshold;
-
-  MaximumFeeThresholdException(this.maximumThreshold)
-    : super('Maximum fee threshold is $maximumThreshold%');
-
-  String displayMessage([AppLocalizations? loc]) {
-    if (loc == null) {
-      return 'Maximum fee threshold is $maximumThreshold%';
-    }
-    return loc.autoswapMaximumFeeError(maximumThreshold.toString());
-  }
-}
-
-class AutoSwapProcessException extends BullException {
-  final Object? error;
-
-  AutoSwapProcessException(super.message, {this.error});
-
-  @override
-  String toString() => error != null ? '$message: $error' : message;
-}
 
 class FeeBlockException extends BullException {
   final double currentFeePercent;

lib/core/swaps/domain/entity/auto_swap.dart

@@ -3,6 +3,15 @@ import 'package:freezed_annotation/freezed_annotation.dart';
 part 'auto_swap.freezed.dart';
 part 'auto_swap.g.dart';
 
+/// Which rule a set of auto swap settings breaks, in the order they are
+/// checked. Callers map this to whatever they show the user.
+enum AutoSwapSettingsViolation {
+  recipientWalletMissing,
+  balanceThresholdTooLow,
+  triggerBalanceTooLow,
+  feeThresholdTooHigh,
+}
+
 @freezed
 sealed class AutoSwap with _$AutoSwap {
   const factory AutoSwap({
@@ -21,6 +30,56 @@ sealed class AutoSwap with _$AutoSwap {
   factory AutoSwap.fromJson(Map<String, dynamic> json) =>
       _$AutoSwapFromJson(json);
 
+  /// Below this a swap would move less than it costs in fees.
+  static const int minimumBalanceThresholdSats = 50000;
+
+  /// Accepting a fee ceiling above this is almost certainly a mistake.
+  static const int maximumFeeThresholdPercent = 10;
+
+  /// Applied when a fee ceiling cannot be determined.
+  static const double defaultFeeThresholdPercent = 3.0;
+
+  static bool isBalanceThresholdTooLow(int balanceThresholdSats) =>
+      balanceThresholdSats < minimumBalanceThresholdSats;
+
+  /// A swap has to leave the wallet at its target, so the trigger must be at
+  /// least twice the target — otherwise a swap would fire and immediately
+  /// leave the balance below where it started.
+  static bool isTriggerBalanceTooLow({
+    required int balanceThresholdSats,
+    required int triggerBalanceSats,
+  }) => triggerBalanceSats < 2 * balanceThresholdSats;
+
+  static bool isFeeThresholdTooHigh(double feeThresholdPercent) =>
+      feeThresholdPercent > maximumFeeThresholdPercent;
+
+  /// The first rule these settings break, or null when they are acceptable.
+  ///
+  /// Deliberately not enforced in the constructor: these settings are
+  /// persisted and deserialized, so a row written by an older version must
+  /// still load even if it would no longer be accepted.
+  AutoSwapSettingsViolation? get violation {
+    // Disabled settings are inert. Re-enabling validates the complete form.
+    if (!enabled) return null;
+
+    if (recipientWalletId == null) {
+      return AutoSwapSettingsViolation.recipientWalletMissing;
+    }
+    if (isBalanceThresholdTooLow(balanceThresholdSats)) {
+      return AutoSwapSettingsViolation.balanceThresholdTooLow;
+    }
+    if (isTriggerBalanceTooLow(
+      balanceThresholdSats: balanceThresholdSats,
+      triggerBalanceSats: triggerBalanceSats,
+    )) {
+      return AutoSwapSettingsViolation.triggerBalanceTooLow;
+    }
+    if (isFeeThresholdTooHigh(feeThresholdPercent)) {
+      return AutoSwapSettingsViolation.feeThresholdTooHigh;
+    }
+    return null;
+  }
+
   bool passedRequiredBalance(int balanceSat) {
     return balanceSat >= triggerBalanceSats && enabled;
   }

lib/features/autoswap/autoswap_locator.dart

@@ -2,19 +2,38 @@ import 'package:bb_mobile/core/settings/domain/get_settings_usecase.dart';
 import 'package:bb_mobile/core/swaps/domain/usecases/get_auto_swap_settings_usecase.dart';
 import 'package:bb_mobile/core/swaps/domain/usecases/save_auto_swap_settings_usecase.dart';
 import 'package:bb_mobile/core/wallet/data/repositories/wallet_repository.dart';
+import 'package:bb_mobile/features/autoswap/domain/usecases/load_autoswap_settings_usecase.dart';
+import 'package:bb_mobile/features/autoswap/domain/usecases/save_autoswap_settings_usecase.dart';
 import 'package:bb_mobile/features/autoswap/presentation/autoswap_settings_cubit.dart';
 import 'package:get_it/get_it.dart';
 
 class AutoSwapLocator {
   static void setup(GetIt locator) {
-    // Register the cubit
-    locator.registerFactory<AutoSwapSettingsCubit>(
-      () => AutoSwapSettingsCubit(
+    registerUsecases(locator);
+    registerBlocs(locator);
+  }
+
+  static void registerUsecases(GetIt locator) {
+    locator.registerFactory<LoadAutoswapSettingsUsecase>(
+      () => LoadAutoswapSettingsUsecase(
         getAutoSwapSettingsUsecase: locator<GetAutoSwapSettingsUsecase>(),
-        saveAutoSwapSettingsUsecase: locator<SaveAutoSwapSettingsUsecase>(),
         getSettingsUsecase: locator<GetSettingsUsecase>(),
         walletRepository: locator<WalletRepository>(),
       ),
     );
+    locator.registerFactory<SaveAutoswapSettingsUsecase>(
+      () => SaveAutoswapSettingsUsecase(
+        saveAutoSwapSettingsUsecase: locator<SaveAutoSwapSettingsUsecase>(),
+      ),
+    );
+  }
+
+  static void registerBlocs(GetIt locator) {
+    locator.registerFactory<AutoSwapSettingsCubit>(
+      () => AutoSwapSettingsCubit(
+        loadAutoswapSettingsUsecase: locator<LoadAutoswapSettingsUsecase>(),
+        saveAutoswapSettingsUsecase: locator<SaveAutoswapSettingsUsecase>(),
+      ),
+    );
   }
 }

lib/features/autoswap/domain/autoswap_failure.dart

@@ -0,0 +1,47 @@
+import 'package:bb_mobile/core/failures/failure.dart';
+
+sealed class AutoswapFailure extends Failure {
+  const AutoswapFailure([super.logMessage]);
+}
+
+/// The stored settings, the wallet list or the app settings could not be read,
+/// so the form cannot be populated.
+final class AutoswapSettingsUnavailableFailure extends AutoswapFailure {
+  const AutoswapSettingsUnavailableFailure([super.logMessage]);
+}
+
+/// Writing the settings failed.
+final class AutoswapSettingsSaveFailure extends AutoswapFailure {
+  const AutoswapSettingsSaveFailure([super.logMessage]);
+}
+
+/// Auto swap is being enabled without a wallet to send the swapped funds to.
+/// Only enforced while enabling — disabling needs no recipient.
+final class AutoswapRecipientWalletRequiredFailure extends AutoswapFailure {
+  const AutoswapRecipientWalletRequiredFailure();
+}
+
+/// The target balance is below the minimum a swap can be made for.
+///
+/// Carries the limit in sats because the message states it. The *unit* it is
+/// rendered in is the user's current display preference, so that choice stays
+/// in presentation — `BitcoinUnit` lives in a Flutter-importing file and must
+/// not reach this layer.
+final class AutoswapBalanceThresholdTooLowFailure extends AutoswapFailure {
+  final int minimumSats;
+
+  const AutoswapBalanceThresholdTooLowFailure(this.minimumSats);
+}
+
+/// The trigger balance is not at least twice the target balance, so a swap
+/// would leave the wallet below its target immediately.
+final class AutoswapTriggerBalanceTooLowFailure extends AutoswapFailure {
+  const AutoswapTriggerBalanceTooLowFailure();
+}
+
+/// The accepted fee ceiling is above what we allow to be set.
+final class AutoswapFeeThresholdTooHighFailure extends AutoswapFailure {
+  final int maximumPercent;
+
+  const AutoswapFeeThresholdTooHighFailure(this.maximumPercent);
+}

lib/features/autoswap/domain/usecases/load_autoswap_settings_usecase.dart

@@ -0,0 +1,61 @@
+import 'package:bb_mobile/core/settings/domain/get_settings_usecase.dart';
+import 'package:bb_mobile/core/settings/domain/settings_entity.dart';
+import 'package:bb_mobile/core/swaps/domain/entity/auto_swap.dart';
+import 'package:bb_mobile/core/swaps/domain/usecases/get_auto_swap_settings_usecase.dart';
+import 'package:bb_mobile/core/utils/logger.dart';
+import 'package:bb_mobile/core/utils/result.dart';
+import 'package:bb_mobile/core/wallet/data/repositories/wallet_repository.dart';
+import 'package:bb_mobile/core/wallet/domain/entities/wallet.dart';
+import 'package:bb_mobile/features/autoswap/domain/autoswap_failure.dart';
+import 'package:meta/meta.dart';
+
+/// Everything the settings form needs to populate itself.
+typedef AutoswapSettingsData = ({
+  AutoSwap settings,
+  BitcoinUnit bitcoinUnit,
+  List<Wallet> bitcoinWallets,
+  String? recipientWalletId,
+});
+
+class LoadAutoswapSettingsUsecase {
+  final GetAutoSwapSettingsUsecase _getAutoSwapSettingsUsecase;
+  final GetSettingsUsecase _getSettingsUsecase;
+  final WalletRepository _walletRepository;
+
+  const LoadAutoswapSettingsUsecase({
+    required this._getAutoSwapSettingsUsecase,
+    required this._getSettingsUsecase,
+    required this._walletRepository,
+  });
+
+  @useResult
+  Future<Result<AutoswapSettingsData, AutoswapFailure>> execute() async {
+    try {
+      final appSettings = await _getSettingsUsecase.execute();
+      final autoSwapSettings = await _getAutoSwapSettingsUsecase.execute();
+
+      final wallets = await _walletRepository.getWallets(
+        environment: appSettings.environment,
+      );
+      final bitcoinWallets = wallets.where((w) => !w.isLiquid).toList();
+      final defaultBitcoinWallet = bitcoinWallets
+          .where((w) => w.isDefault)
+          .firstOrNull;
+
+      return Ok((
+        settings: autoSwapSettings,
+        bitcoinUnit: appSettings.bitcoinUnit,
+        bitcoinWallets: bitcoinWallets,
+        recipientWalletId:
+            autoSwapSettings.recipientWalletId ?? defaultBitcoinWallet?.id,
+      ));
+    } catch (e, st) {
+      log.severe(
+        message: 'Failed to load auto swap settings',
+        error: e,
+        trace: st,
+      );
+      return Err(AutoswapSettingsUnavailableFailure(e.runtimeType.toString()));
+    }
+  }
+}

lib/features/autoswap/domain/usecases/save_autoswap_settings_usecase.dart

@@ -0,0 +1,52 @@
+import 'package:bb_mobile/core/swaps/domain/entity/auto_swap.dart';
+import 'package:bb_mobile/core/swaps/domain/usecases/save_auto_swap_settings_usecase.dart';
+import 'package:bb_mobile/core/utils/logger.dart';
+import 'package:bb_mobile/core/utils/result.dart';
+import 'package:bb_mobile/features/autoswap/domain/autoswap_failure.dart';
+import 'package:meta/meta.dart';
+
+class SaveAutoswapSettingsUsecase {
+  final SaveAutoSwapSettingsUsecase _saveAutoSwapSettingsUsecase;
+
+  const SaveAutoswapSettingsUsecase({
+    required this._saveAutoSwapSettingsUsecase,
+  });
+
+  /// Refuses settings the entity rejects, then writes them.
+  ///
+  /// Validating here rather than in the caller means no future caller can
+  /// persist settings that break the rules.
+  @useResult
+  Future<Result<void, AutoswapFailure>> execute(AutoSwap settings) async {
+    final violation = settings.violation;
+    if (violation != null) return Err(_failureFor(violation));
+
+    try {
+      await _saveAutoSwapSettingsUsecase.execute(settings);
+      return const Ok(null);
+    } catch (e, st) {
+      log.severe(
+        message: 'Failed to save auto swap settings',
+        error: e,
+        trace: st,
+      );
+      return Err(AutoswapSettingsSaveFailure(e.runtimeType.toString()));
+    }
+  }
+
+  AutoswapFailure _failureFor(AutoSwapSettingsViolation violation) =>
+      switch (violation) {
+        AutoSwapSettingsViolation.recipientWalletMissing =>
+          const AutoswapRecipientWalletRequiredFailure(),
+        AutoSwapSettingsViolation.balanceThresholdTooLow =>
+          const AutoswapBalanceThresholdTooLowFailure(
+            AutoSwap.minimumBalanceThresholdSats,
+          ),
+        AutoSwapSettingsViolation.triggerBalanceTooLow =>
+          const AutoswapTriggerBalanceTooLowFailure(),
+        AutoSwapSettingsViolation.feeThresholdTooHigh =>
+          const AutoswapFeeThresholdTooHighFailure(
+            AutoSwap.maximumFeeThresholdPercent,
+          ),
+      };
+}

lib/features/autoswap/presentation/autoswap_failure_l10n.dart

@@ -0,0 +1,27 @@
+import 'package:bb_mobile/core/settings/domain/settings_entity.dart';
+import 'package:bb_mobile/core/utils/amount_conversions.dart';
+import 'package:bb_mobile/core/utils/build_context_x.dart';
+import 'package:bb_mobile/features/autoswap/domain/autoswap_failure.dart';
+import 'package:flutter/widgets.dart';
+
+extension AutoswapFailureL10n on AutoswapFailure {
+  String toTranslated(BuildContext context, {BitcoinUnit? unit}) =>
+      switch (this) {
+        AutoswapSettingsUnavailableFailure() =>
+          context.loc.autoswapLoadSettingsError,
+        AutoswapSettingsSaveFailure() =>
+          context.loc.autoswapUpdateSettingsError,
+        AutoswapRecipientWalletRequiredFailure() =>
+          context.loc.autoswapSelectWalletError,
+        AutoswapBalanceThresholdTooLowFailure(:final minimumSats) =>
+          unit == BitcoinUnit.btc
+              ? context.loc.autoswapMinimumThresholdErrorBtc(
+                  ConvertAmount.satsToBtc(minimumSats).toString(),
+                )
+              : context.loc.autoswapMinimumThresholdErrorSats('$minimumSats'),
+        AutoswapTriggerBalanceTooLowFailure() =>
+          context.loc.autoswapTriggerBalanceError,
+        AutoswapFeeThresholdTooHighFailure(:final maximumPercent) =>
+          context.loc.autoswapMaximumFeeError('$maximumPercent'),
+      };
+}