unified gateway interfaces

frontend/pshared/lib/data/dto/payment/intent/payment.dart

@@ -20,6 +20,9 @@ class PaymentIntentDTO {
   @JsonKey(name: 'settlement_mode')
   final String? settlementMode;
 
+  @JsonKey(name: 'settlement_currency')
+  final String? settlementCurrency;
+
   final Map<String, String>? attributes;
   final CustomerDTO? customer;
 
@@ -30,6 +33,7 @@ class PaymentIntentDTO {
     this.amount,
     this.fx,
     this.settlementMode,
+    this.settlementCurrency,
     this.attributes,
     this.customer,
   });

frontend/pshared/lib/data/mapper/payment/intent/payment.dart

@@ -15,6 +15,7 @@ extension PaymentIntentMapper on PaymentIntent {
     amount: amount?.toDTO(),
     fx: fx?.toDTO(),
     settlementMode: settlementModeToValue(settlementMode),
+    settlementCurrency: settlementCurrency,
     attributes: attributes,
     customer: customer?.toDTO(),
   );
@@ -28,6 +29,7 @@ extension PaymentIntentDTOMapper on PaymentIntentDTO {
     amount: amount?.toDomain(),
     fx: fx?.toDomain(),
     settlementMode: settlementModeFromValue(settlementMode),
+    settlementCurrency: settlementCurrency,
     attributes: attributes,
     customer: customer?.toDomain(),
   );

frontend/pshared/lib/models/payment/intent.dart

@@ -13,6 +13,7 @@ class PaymentIntent {
   final Money? amount;
   final FxIntent? fx;
   final SettlementMode settlementMode;
+  final String? settlementCurrency;
   final Map<String, String>? attributes;
   final Customer? customer;
 
@@ -23,6 +24,7 @@ class PaymentIntent {
     this.amount,
     this.fx,
     this.settlementMode = SettlementMode.unspecified,
+    this.settlementCurrency,
     this.attributes,
     this.customer,
   });

frontend/pshared/lib/provider/payment/quotation.dart

@@ -51,25 +51,28 @@ class QuotationProvider extends ChangeNotifier {
         recipient: recipients.currentObject,
         method: method,
       );
+      final amount = Money(
+        amount: payment.amount.toString(),
+        // TODO: adapt to possible other sources
+        currency: currencyCodeToString(wallets.selectedWallet!.currency),
+      );
+      final fxIntent = FxIntent(
+        pair: CurrencyPair(
+          base: currencyCodeToString(wallets.selectedWallet!.currency),
+          quote: 'RUB', // TODO: exentd target currencies
+        ),
+        side: FxSide.sellBaseBuyQuote,
+      );
       getQuotation(PaymentIntent(
         kind: PaymentKind.payout,
-        amount: Money(
-          amount: payment.amount.toString(), 
-          // TODO: adapt to possible other sources
-          currency: currencyCodeToString(wallets.selectedWallet!.currency),
-        ),
+        amount: amount,
         destination: method.data,
         source: ManagedWalletPaymentMethod(
           managedWalletRef: wallets.selectedWallet!.id,
         ),
-        fx: FxIntent(
-          pair: CurrencyPair(
-            base: currencyCodeToString(wallets.selectedWallet!.currency), 
-            quote: 'RUB', // TODO: exentd target currencies
-          ),
-          side: FxSide.sellBaseBuyQuote,
-        ),
+        fx: fxIntent,
         settlementMode: payment.payerCoversFee ? SettlementMode.fixReceived : SettlementMode.fixSource,
+        settlementCurrency: _resolveSettlementCurrency(amount: amount, fx: fxIntent),
         customer: customer,
       ));
     }
@@ -83,6 +86,30 @@ class QuotationProvider extends ChangeNotifier {
   Asset? get total => quotation == null ? null : createAsset(quotation!.debitAmount!.currency, quotation!.debitAmount!.amount);
   Asset? get recipientGets => quotation == null ? null : createAsset(quotation!.expectedSettlementAmount!.currency, quotation!.expectedSettlementAmount!.amount);
 
+  String _resolveSettlementCurrency({
+    required Money amount,
+    required FxIntent? fx,
+  }) {
+    final pair = fx?.pair;
+    if (pair != null) {
+      switch (fx?.side ?? FxSide.unspecified) {
+        case FxSide.buyBaseSellQuote:
+          if (pair.base.isNotEmpty) return pair.base;
+          break;
+        case FxSide.sellBaseBuyQuote:
+          if (pair.quote.isNotEmpty) return pair.quote;
+          break;
+        case FxSide.unspecified:
+          break;
+      }
+      if (amount.currency == pair.base && pair.quote.isNotEmpty) return pair.quote;
+      if (amount.currency == pair.quote && pair.base.isNotEmpty) return pair.base;
+      if (pair.quote.isNotEmpty) return pair.quote;
+      if (pair.base.isNotEmpty) return pair.base;
+    }
+    return amount.currency;
+  }
+
   Customer _buildCustomer({
     required Recipient? recipient,
     required PaymentMethod method,