Automate spend from spark to EX-address in Qt

src/qt/sendcoinsdialog.cpp

@@ -292,7 +292,6 @@ void SendCoinsDialog::on_sendButton_clicked()
     }
 
     // prepare transaction for getting txFee earlier
-    WalletModelTransaction currentTransaction(recipients);
     std::vector<WalletModelTransaction> transactions;
     WalletModel::SendCoinsReturn prepareStatus;
     std::vector<std::pair<CWalletTx, CAmount>> wtxAndFees;
@@ -310,13 +309,68 @@ void SendCoinsDialog::on_sendButton_clicked()
         ctrl.nConfirmTarget = 0;
 
     int sparkAddressCount = 0;
+    int exchangeAddressCount = 0;
     for(int i = 0; i < recipients.size(); ++i){
-        bool check = model->validateSparkAddress(recipients[i].address);
-        if(check) {
+        if (model->validateSparkAddress(recipients[i].address))
             sparkAddressCount++;
+        if (model->validateExchangeAddress(recipients[i].address))
+            exchangeAddressCount++;
+    }
+
+    bool fGoThroughTransparentAddress = false;
+    __decltype(recipients) exchangeRecipients;
+    CScript intermediateAddressScript;
+    CAmount extraFee = 0;
+
+    if (fAnonymousMode && exchangeAddressCount > 0) {
+        CAmount exchangeAddressAmount = 0;
+        // if the transaction is performed in two stages through the intermediate address we need to calculate the size of the second transaction
+        uint32_t secondTxSize = 8 /*CTransaction: nVersion, nLockTime*/ + 1 /*vinSize*/ + 148 /*vin[0]*/ + 20 /*safety*/ + 1 /*voutSize*/;
+
+        fGoThroughTransparentAddress = true;
+
+        // remove exchange addresses from recipients array and add them to exchangeRecipients array
+        for(int i = 0; i < recipients.size(); ){
+            if (model->validateExchangeAddress(recipients[i].address)) {
+                exchangeAddressAmount += recipients[i].amount;
+                // we use different fee calculation system and therefore can't reliably do the calculation
+                // of fee for the second transaction if some of recipients have this flag set
+                recipients[i].fSubtractFeeFromAmount = false;
+                exchangeRecipients.push_back(recipients[i]);
+
+                secondTxSize += 8 /*amount*/ + 1 /*scriptSize*/ + 26 /*scriptPubKey*/;
+
+                recipients.erase(recipients.begin() + i);
+            }
+            else {
+                ++i;
+            }
+        }
+
+        LOCK2(cs_main, pwalletMain->cs_wallet);
+        // create a new transparent address and add it to the recipients array
+        if (!pwalletMain->IsLocked()) {
+            pwalletMain->TopUpKeyPool();
+        }
+        CPubKey newKey;
+        if (!pwalletMain->GetKeyFromPool(newKey)) {
+            fNewRecipientAllowed = true;
+            return;
         }
+        pwalletMain->SetAddressBook(newKey.GetID(), "", "receive");
+        intermediateAddressScript = GetScriptForDestination(newKey.GetID());
+
+        extraFee = CWallet::GetMinimumFee(secondTxSize, 0, mempool);
+
+        SendCoinsRecipient newRecipient;        
+        newRecipient.address = CBitcoinAddress(newKey.GetID()).ToString().c_str();
+        newRecipient.amount = exchangeAddressAmount + extraFee;
+        newRecipient.fSubtractFeeFromAmount = false;
+        recipients.push_back(newRecipient);
     }
 
+    WalletModelTransaction currentTransaction(recipients);
+
     CAmount mintSparkAmount = 0;
     CAmount txFee = 0;
     CAmount totalAmount = 0;
@@ -364,6 +418,14 @@ void SendCoinsDialog::on_sendButton_clicked()
         return;
     }
 
+    // If the transaction is performed in two stages through the intermediate address we need to show the real
+    // recipients (for informational purposes), replacing the intermediate transparent address with the exchange address(es)
+    __decltype(recipients) realRecipients = recipients;
+    if (fGoThroughTransparentAddress) {
+        realRecipients.erase(realRecipients.end() - 1);
+        realRecipients.append(exchangeRecipients);
+    }
+
     // Format confirmation message
     QStringList formatted;
     if ((fAnonymousMode == false) && (recipients.size() == sparkAddressCount) && spark::IsSparkAllowed()) 
@@ -407,7 +469,7 @@ void SendCoinsDialog::on_sendButton_clicked()
             formatted.append(recipientElement);
         }
     } else if ((fAnonymousMode == true) && (recipients.size() == 1) && spark::IsSparkAllowed()) {
-        for (auto &rcp : recipients)
+        for (auto &rcp : realRecipients)
         {
             // generate bold amount string
             CAmount namount = rcp.amount;
@@ -434,7 +496,7 @@ void SendCoinsDialog::on_sendButton_clicked()
             formatted.append(recipientElement);
         }
     } else {
-        for (const SendCoinsRecipient &rcp : currentTransaction.getRecipients())
+        for (auto &rcp : realRecipients)
         {
             // generate bold amount string
             QString amount = "<b>" + BitcoinUnits::formatHtmlWithUnit(model->getOptionsModel()->getDisplayUnit(), rcp.amount);
@@ -459,6 +521,14 @@ void SendCoinsDialog::on_sendButton_clicked()
             formatted.append(recipientElement);
         }
     }
+
+    if (fGoThroughTransparentAddress) {
+        QString transparentAddress = "<span style='font-family: monospace;'>" + recipients[recipients.size()-1].address + "</span>";
+        formatted.append("<br />");
+        formatted.append(tr("EX-addresses can only receive FIRO from transparent addresses.<br /><br />"
+            "Your FIRO will go from Spark to a newly generated transparent address %1 and then immediately be sent to the EX-address.").arg(transparentAddress));
+    }
+
     QString questionString = tr("Are you sure you want to send?");
     questionString.append("<br /><br />%1");
     double txSize;
@@ -484,6 +554,15 @@ void SendCoinsDialog::on_sendButton_clicked()
 
         // append transaction size
         questionString.append(" (" + QString::number(txSize / 1000) + " kB)");
+
+        if (fGoThroughTransparentAddress) {
+            QString feeString;
+            feeString.append("<span style='color:#aa0000;'>");
+            feeString.append(BitcoinUnits::formatHtmlWithUnit(model->getOptionsModel()->getDisplayUnit(), extraFee));
+            feeString.append("</span>");
+
+            questionString.append(tr(". An additional transaction fee of %1 will apply to complete the send from the transparent address to the EX-address.").arg(feeString));
+        }
     }
 
     // add total amount in all subdivision units
@@ -556,6 +635,53 @@ void SendCoinsDialog::on_sendButton_clicked()
         CoinControlDialog::coinControl->UnSelectAll();
         coinControlUpdateLabels();
     }
+
+    // Launch the second stage of the transaction if needed
+    if (fGoThroughTransparentAddress) {
+        // prepare the coin control so the transaction will use (by default) only the transparent address
+        // created in the first stage
+        COutPoint outpoint;
+        outpoint.hash = currentTransaction.getTransaction()->GetHash();
+        outpoint.n = UINT_MAX;
+
+        const auto &vout = currentTransaction.getTransaction()->tx->vout;
+        for (size_t i = 0; i < vout.size(); i++) {
+            if (vout[i].scriptPubKey == intermediateAddressScript) {
+                outpoint.n = i;
+                break;
+            }
+        }
+
+        if (outpoint.n == UINT_MAX) {
+            sendStatus.status = WalletModel::InvalidAddress;
+            sendStatus.reasonCommitFailed = "Intermediate address was not found in the transaction";
+            fNewRecipientAllowed = true;
+            return;
+        }
+
+        CCoinControl ctrl;
+        ctrl.fAllowOtherInputs = false;
+        ctrl.fNoChange = true;
+        ctrl.Select(outpoint);
+
+        WalletModelTransaction  secondTransaction(exchangeRecipients);
+
+        prepareStatus = model->prepareTransaction(secondTransaction, &ctrl);
+
+        // process prepareStatus and on error generate message shown to user
+        processSendCoinsReturn(prepareStatus,
+            BitcoinUnits::formatWithUnit(model->getOptionsModel()->getDisplayUnit(), currentTransaction.getTransactionFee()));
+
+        if(prepareStatus.status != WalletModel::OK) {
+            fNewRecipientAllowed = true;
+            return;
+        }
+
+        sendStatus = model->sendCoins(secondTransaction);
+        // process sendStatus and on error generate message shown to user
+        processSendCoinsReturn(sendStatus);
+    }
+
     fNewRecipientAllowed = true;
 }
 

src/qt/walletmodel.cpp

@@ -272,6 +272,12 @@ bool WalletModel::validateAddress(const QString &address)
     return addressParsed.IsValid();
 }
 
+bool WalletModel::validateExchangeAddress(const QString &address)
+{
+    CBitcoinAddress addressParsed(address.toStdString());
+    return addressParsed.IsValid() && addressParsed.Get().type() == typeid(CExchangeKeyID);
+}
+
 WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransaction &transaction, const CCoinControl *coinControl)
 {
     CAmount total = 0;

src/qt/walletmodel.h

@@ -153,6 +153,7 @@ class WalletModel : public QObject
 
     // Check address for validity
     bool validateAddress(const QString &address);
+    bool validateExchangeAddress(const QString &address);
     bool validateSparkAddress(const QString &address);
     std::pair<CAmount, CAmount> getSparkBalance();
 

src/wallet/coincontrol.h

@@ -24,6 +24,8 @@ class CCoinControl
 {
 public:
     CTxDestination destChange;
+    //! If true, don't use any change
+    bool fNoChange;
     //! If false, allows unselected inputs, but requires all selected inputs be used
     bool fAllowOtherInputs;
     //! Includes watch only addresses which match the ISMINE_WATCH_SOLVABLE criteria
@@ -49,6 +51,7 @@ class CCoinControl
     void SetNull()
     {
         destChange = CNoDestination();
+        fNoChange = false;
         fAllowOtherInputs = false;
         fRequireAllInputs = true;
         fAllowWatchOnly = false;

src/wallet/wallet.cpp

@@ -4450,7 +4450,7 @@ bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletT
                 const CAmount nChange = nValueIn - nValueToSelect;
                 CTxOut newTxOut;
 
-                if (nChange > 0)
+                if (nChange > 0 && !(coinControl && coinControl->fNoChange))
                 {
                     // Fill a vout to ourself
                     // TODO: pass in scriptChange instead of reservekey so