Prevent a P2SH address being funded for a trade if there is an unconfirmed buy or cancel request in progress for it already.

This prevents foreign coins from leaving the local wallet when there is a high probability that the trade will fail, and therefore should reduce the chances of losing transaction fees due to refunds.

Whenever this occurs, the UI will show "Trade has an existing buy request or is pending cancellation." after clicking Buy.

src/main/java/org/qortal/api/resource/CrossChainTradeBotResource.java

@@ -11,6 +11,7 @@ import io.swagger.v3.oas.annotations.security.SecurityRequirement;
 import io.swagger.v3.oas.annotations.tags.Tag;
 
 import java.util.List;
+import java.util.Objects;
 import java.util.stream.Collectors;
 
 import javax.servlet.http.HttpServletRequest;
@@ -38,9 +39,12 @@ import org.qortal.crypto.Crypto;
 import org.qortal.data.at.ATData;
 import org.qortal.data.crosschain.CrossChainTradeData;
 import org.qortal.data.crosschain.TradeBotData;
+import org.qortal.data.transaction.MessageTransactionData;
+import org.qortal.data.transaction.TransactionData;
 import org.qortal.repository.DataException;
 import org.qortal.repository.Repository;
 import org.qortal.repository.RepositoryManager;
+import org.qortal.transaction.Transaction;
 import org.qortal.utils.Base58;
 import org.qortal.utils.NTP;
 
@@ -223,6 +227,17 @@ public class CrossChainTradeBotResource {
 			if (crossChainTradeData.mode != AcctMode.OFFERING)
 				throw ApiExceptionFactory.INSTANCE.createException(request, ApiError.INVALID_CRITERIA);
 
+			// Check if there is a buy or a cancel request in progress for this trade
+			List<Transaction.TransactionType> txTypes = List.of(Transaction.TransactionType.MESSAGE);
+			List<TransactionData> unconfirmed = repository.getTransactionRepository().getUnconfirmedTransactions(txTypes, null, 0, 0, false);
+			for (TransactionData  transactionData : unconfirmed) {
+				MessageTransactionData messageTransactionData = (MessageTransactionData) transactionData;
+				if (Objects.equals(messageTransactionData.getRecipient(), atAddress)) {
+					// There is a pending request for this trade, so block this buy attempt to reduce the risk of refunds
+					throw ApiExceptionFactory.INSTANCE.createCustomException(request, ApiError.INVALID_CRITERIA, "Trade has an existing buy request or is pending cancellation.");
+				}
+			}
+
 			AcctTradeBot.ResponseResult result = TradeBot.getInstance().startResponse(repository, atData, acct, crossChainTradeData,
 					tradeBotRespondRequest.foreignKey, tradeBotRespondRequest.receivingAddress);