CW-1146-Enable-Zano-buy-sell-for-DFX (#2458)

* feat(CW-1148): Add Zano wallet support for message

* refactor(CW-1148): Simplify `signMessage` logic in Zano wallet API

* fix: remove unsupported wallet types from DFX Buy provider

* fix: correct DFX Buy provider parameter name from `amount` to `amount-in`

cw_zano/lib/zano_wallet.dart

@@ -59,9 +59,8 @@ abstract class ZanoWalletBase
   String get password => _password;
 
   @override
-  Future<String> signMessage(String message, {String? address = null}) {
-    throw UnimplementedError();
-  }
+  Future<String> signMessage(String message, {String? address = null}) =>
+      super.signMessage(message, address: address);
 
   @override
   Future<bool> verifyMessage(String message, String signature, {String? address = null}) {

cw_zano/lib/zano_wallet_api.dart

@@ -401,6 +401,35 @@ mixin ZanoWalletApi {
     throw TransferException('Transfer error, empty result');
   }
 
+  Future<String> signMessage(String message, {String? address = null}) async {
+    try {
+      final messageBase64 = convert.base64.encode(convert.utf8.encode(message));
+      final response = await invokeMethod('sign_message', {'buff': messageBase64});
+      final responseData = convert.jsonDecode(response) as Map<String, dynamic>;
+
+      if (responseData['error'] != null) {
+        printV('ZANO sign_message error: ${responseData['error']}');
+        throw Exception('Zano sign_message failed: ${responseData['error']}');
+      }
+
+      final result = responseData['result'] as Map<String, dynamic>?;
+      if (result == null) {
+        throw Exception('Invalid response from sign_message');
+      }
+
+      final signature = result['sig'] as String?;
+
+      if (signature == null) {
+        throw Exception('No signature in response');
+      }
+
+      return signature;
+    } catch (e) {
+      printV('ZANO signMessage error: $e');
+      rethrow;
+    }
+  }
+
   void _checkForErrors(Map<String, dynamic>? map) {
     if (map == null) {
       throw ZanoWalletException('Empty response');
@@ -510,4 +539,4 @@ Future<String> _closeWallet(int hWallet) async {
   return str;
 }
 
-Map<String, List<int>> debugCallLength() => zano.debugCallLength;
+Map<String, List<int>> debugCallLength() => zano.debugCallLength;

lib/buy/dfx/dfx_buy_provider.dart

@@ -62,9 +62,9 @@ class DFXBuyProvider extends BuyProvider {
   String get blockchain {
     switch (wallet.type) {
       case WalletType.bitcoin:
-      case WalletType.bitcoinCash:
-      case WalletType.litecoin:
         return 'Bitcoin';
+      case WalletType.zano:
+        return 'Zano';
       default:
         return walletTypeToString(wallet.type);
     }
@@ -131,6 +131,7 @@ class DFXBuyProvider extends BuyProvider {
       case WalletType.litecoin:
       case WalletType.bitcoin:
       case WalletType.bitcoinCash:
+      case WalletType.zano:
         return await wallet.signMessage(message, address: walletAddress);
       default:
         throw Exception("WalletType is not available for DFX ${wallet.type}");
@@ -345,7 +346,7 @@ class DFXBuyProvider extends BuyProvider {
         'asset-out': isBuyAction ? quote.cryptoCurrency.toString() : quote.fiatCurrency.toString(),
         'blockchain': blockchain,
         'asset-in': isBuyAction ? quote.fiatCurrency.toString() : quote.cryptoCurrency.toString(),
-        'amount': amount.toString() //TODO: Amount does not work
+        'amount-in': amount.toString()
       });
 
       if (await canLaunchUrl(uri)) {