Subtract fee from amount

Fixes #2724 and #1570.

Adds the
automatically-subtract-the-fee-from-the-amount-and-send-whats-left
feature to the GUI and RPC (sendtoaddress,sendmany).

1 files changed, 17 insertions, 5 deletions

diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 79f5191fc0..1baa5eb932 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -6,6 +6,7 @@
 
 #include "addresstablemodel.h"
 #include "guiconstants.h"
+#include "guiutil.h"
 #include "paymentserver.h"
 #include "recentrequeststablemodel.h"
 #include "transactiontablemodel.h"
@@ -192,8 +193,9 @@ bool WalletModel::validateAddress(const QString &address)
 WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransaction &transaction, const CCoinControl *coinControl)
 {
     CAmount total = 0;
+    bool fSubtractFeeFromAmount = false;
     QList<SendCoinsRecipient> recipients = transaction.getRecipients();
-    std::vector<std::pair<CScript, CAmount> > vecSend;
+    std::vector<CRecipient> vecSend;
 
     if(recipients.empty())
     {
@@ -206,6 +208,9 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
     // Pre-check input data for validity
     foreach(const SendCoinsRecipient &rcp, recipients)
     {
+        if (rcp.fSubtractFeeFromAmount)
+            fSubtractFeeFromAmount = true;
+
         if (rcp.paymentRequest.IsInitialized())
         {   // PaymentRequest...
             CAmount subtotal = 0;
@@ -217,7 +222,9 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
                 subtotal += out.amount();
                 const unsigned char* scriptStr = (const unsigned char*)out.script().data();
                 CScript scriptPubKey(scriptStr, scriptStr+out.script().size());
-                vecSend.push_back(std::pair<CScript, CAmount>(scriptPubKey, out.amount()));
+                CAmount nAmount = out.amount();
+                CRecipient recipient = {scriptPubKey, nAmount, rcp.fSubtractFeeFromAmount};
+                vecSend.push_back(recipient);
             }
             if (subtotal <= 0)
             {
@@ -239,7 +246,8 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
             ++nAddresses;
 
             CScript scriptPubKey = GetScriptForDestination(CBitcoinAddress(rcp.address.toStdString()).Get());
-            vecSend.push_back(std::pair<CScript, CAmount>(scriptPubKey, rcp.amount));
+            CRecipient recipient = {scriptPubKey, rcp.amount, rcp.fSubtractFeeFromAmount};
+            vecSend.push_back(recipient);
 
             total += rcp.amount;
         }
@@ -260,17 +268,21 @@ WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransact
         LOCK2(cs_main, wallet->cs_wallet);
 
         transaction.newPossibleKeyChange(wallet);
+
         CAmount nFeeRequired = 0;
+        int nChangePosRet = -1;
         std::string strFailReason;
 
         CWalletTx *newTx = transaction.getTransaction();
         CReserveKey *keyChange = transaction.getPossibleKeyChange();
-        bool fCreated = wallet->CreateTransaction(vecSend, *newTx, *keyChange, nFeeRequired, strFailReason, coinControl);
+        bool fCreated = wallet->CreateTransaction(vecSend, *newTx, *keyChange, nFeeRequired, nChangePosRet, strFailReason, coinControl);
         transaction.setTransactionFee(nFeeRequired);
+        if (fSubtractFeeFromAmount && fCreated)
+            transaction.reassignAmounts(nChangePosRet);
 
         if(!fCreated)
         {
-            if((total + nFeeRequired) > nBalance)
+            if(!fSubtractFeeFromAmount && (total + nFeeRequired) > nBalance)
             {
                 return SendCoinsReturn(AmountWithFeeExceedsBalance);
             }