Add change options to fundrawtransaction

3 files changed, 74 insertions, 23 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 5511e9d3ab..5cd57fc385 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -2437,7 +2437,7 @@ UniValue fundrawtransaction(const UniValue& params, bool fHelp)
 
     if (fHelp || params.size() < 1 || params.size() > 2)
         throw runtime_error(
-                            "fundrawtransaction \"hexstring\" includeWatching\n"
+                            "fundrawtransaction \"hexstring\" ( options )\n"
                             "\nAdd inputs to a transaction until it has enough in value to meet its out value.\n"
                             "This will not modify existing inputs, and will add one change output to the outputs.\n"
                             "Note that inputs which were signed may need to be resigned after completion since in/outputs have been added.\n"
@@ -2447,8 +2447,14 @@ UniValue fundrawtransaction(const UniValue& params, bool fHelp)
                             "in the wallet using importaddress or addmultisigaddress (to calculate fees).\n"
                             "Only pay-to-pubkey, multisig, and P2SH versions thereof are currently supported for watch-only\n"
                             "\nArguments:\n"
-                            "1. \"hexstring\"     (string, required) The hex string of the raw transaction\n"
-                            "2. includeWatching (boolean, optional, default false) Also select inputs which are watch only\n"
+                            "1. \"hexstring\"           (string, required) The hex string of the raw transaction\n"
+                            "2. options               (object, optional)\n"
+                            "   {\n"
+                            "     \"changeAddress\"     (string, optional, default pool address) The bitcoin address to receive the change\n"
+                            "     \"changePosition\"    (numeric, optional, default random) The index of the change output\n"
+                            "     \"includeWatching\"   (boolean, optional, default false) Also select inputs which are watch only\n"
+                            "   }\n"
+                            "                         for backward compatibility: passing in a true instzead of an object will result in {\"includeWatching\":true}\n"
                             "\nResult:\n"
                             "{\n"
                             "  \"hex\":       \"value\", (string)  The resulting raw transaction (hex-encoded string)\n"
@@ -2467,7 +2473,40 @@ UniValue fundrawtransaction(const UniValue& params, bool fHelp)
                             + HelpExampleCli("sendrawtransaction", "\"signedtransactionhex\"")
                             );
 
-    RPCTypeCheck(params, boost::assign::list_of(UniValue::VSTR)(UniValue::VBOOL));
+    RPCTypeCheck(params, boost::assign::list_of(UniValue::VSTR));
+
+    CTxDestination changeAddress = CNoDestination();
+    int changePosition = -1;
+    bool includeWatching = false;
+
+    if (params.size() > 1) {
+      if (params[1].type() == UniValue::VBOOL) {
+        // backward compatibility bool only fallback
+        includeWatching = params[1].get_bool();
+      }
+      else {
+        RPCTypeCheck(params, boost::assign::list_of(UniValue::VSTR)(UniValue::VOBJ));
+
+        UniValue options = params[1];
+
+        RPCTypeCheckObj(options, boost::assign::map_list_of("changeAddress", UniValue::VSTR)("changePosition", UniValue::VNUM)("includeWatching", UniValue::VBOOL), true, true);
+
+        if (options.exists("changeAddress")) {
+            CBitcoinAddress address(options["changeAddress"].get_str());
+
+            if (!address.IsValid())
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "changeAddress must be a valid bitcoin address");
+
+            changeAddress = address.Get();
+        }
+
+        if (options.exists("changePosition"))
+            changePosition = options["changePosition"].get_int();
+
+        if (options.exists("includeWatching"))
+            includeWatching = options["includeWatching"].get_bool();
+      }
+    }
 
     // parse hex string from parameter
     CTransaction origTx;
@@ -2477,20 +2516,19 @@ UniValue fundrawtransaction(const UniValue& params, bool fHelp)
     if (origTx.vout.size() == 0)
         throw JSONRPCError(RPC_INVALID_PARAMETER, "TX must have at least one output");
 
-    bool includeWatching = false;
-    if (params.size() > 1)
-        includeWatching = params[1].get_bool();
+    if (changePosition != -1 && (changePosition < 0 || changePosition > origTx.vout.size()))
+        throw JSONRPCError(RPC_INVALID_PARAMETER, "changePosition out of bounds");
 
     CMutableTransaction tx(origTx);
     CAmount nFee;
     string strFailReason;
-    int nChangePos = -1;
-    if(!pwalletMain->FundTransaction(tx, nFee, nChangePos, strFailReason, includeWatching))
+
+    if(!pwalletMain->FundTransaction(tx, nFee, changePosition, strFailReason, includeWatching, changeAddress))
         throw JSONRPCError(RPC_INTERNAL_ERROR, strFailReason);
 
     UniValue result(UniValue::VOBJ);
     result.push_back(Pair("hex", EncodeHexTx(tx)));
-    result.push_back(Pair("changepos", nChangePos));
+    result.push_back(Pair("changepos", changePosition));
     result.push_back(Pair("fee", ValueFromAmount(nFee)));
 
     return result;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index e8c9466710..ee92552168 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1932,7 +1932,7 @@ bool CWallet::SelectCoins(const vector<COutput>& vAvailableCoins, const CAmount&
     return res;
 }
 
-bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount &nFeeRet, int& nChangePosRet, std::string& strFailReason, bool includeWatching)
+bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, const CTxDestination& destChange)
 {
     vector<CRecipient> vecSend;
 
@@ -1944,6 +1944,7 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount &nFeeRet, int& nC
     }
 
     CCoinControl coinControl;
+    coinControl.destChange = destChange;
     coinControl.fAllowOtherInputs = true;
     coinControl.fAllowWatchOnly = includeWatching;
     BOOST_FOREACH(const CTxIn& txin, tx.vin)
@@ -1951,11 +1952,11 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount &nFeeRet, int& nC
 
     CReserveKey reservekey(this);
     CWalletTx wtx;
-    if (!CreateTransaction(vecSend, wtx, reservekey, nFeeRet, nChangePosRet, strFailReason, &coinControl, false))
+    if (!CreateTransaction(vecSend, wtx, reservekey, nFeeRet, nChangePosInOut, strFailReason, &coinControl, false))
         return false;
 
-    if (nChangePosRet != -1)
-        tx.vout.insert(tx.vout.begin() + nChangePosRet, wtx.vout[nChangePosRet]);
+    if (nChangePosInOut != -1)
+        tx.vout.insert(tx.vout.begin() + nChangePosInOut, wtx.vout[nChangePosInOut]);
 
     // Add new txins (keeping original txin scriptSig/order)
     BOOST_FOREACH(const CTxIn& txin, wtx.vin)
@@ -1968,9 +1969,10 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount &nFeeRet, int& nC
 }
 
 bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet,
-                                int& nChangePosRet, std::string& strFailReason, const CCoinControl* coinControl, bool sign)
+                                int& nChangePosInOut, std::string& strFailReason, const CCoinControl* coinControl, bool sign)
 {
     CAmount nValue = 0;
+    int nChangePosRequest = nChangePosInOut;
     unsigned int nSubtractFeeFromAmount = 0;
     BOOST_FOREACH (const CRecipient& recipient, vecSend)
     {
@@ -2036,10 +2038,10 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
             // Start with no fee and loop until there is enough fee
             while (true)
             {
+                nChangePosInOut = nChangePosRequest;
                 txNew.vin.clear();
                 txNew.vout.clear();
                 wtxNew.fFromMe = true;
-                nChangePosRet = -1;
                 bool fFirst = true;
 
                 CAmount nValueToSelect = nValue;
@@ -2159,14 +2161,24 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
                     // add the dust to the fee.
                     if (newTxOut.IsDust(::minRelayTxFee))
                     {
+                        nChangePosInOut = -1;
                         nFeeRet += nChange;
                         reservekey.ReturnKey();
                     }
                     else
                     {
-                        // Insert change txn at random position:
-                        nChangePosRet = GetRandInt(txNew.vout.size()+1);
-                        vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosRet;
+                        if (nChangePosInOut == -1)
+                        {
+                            // Insert change txn at random position:
+                            nChangePosInOut = GetRandInt(txNew.vout.size()+1);
+                        }
+                        else if (nChangePosInOut > txNew.vout.size())
+                        {
+                            strFailReason = _("Change index out of range");
+                            return false;
+                        }
+
+                        vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosInOut;
                         txNew.vout.insert(position, newTxOut);
                     }
                 }
@@ -2842,13 +2854,13 @@ void CWallet::GetScriptForMining(boost::shared_ptr<CReserveScript> &script)
     script->reserveScript = CScript() << ToByteVector(pubkey) << OP_CHECKSIG;
 }
 
-void CWallet::LockCoin(COutPoint& output)
+void CWallet::LockCoin(const COutPoint& output)
 {
     AssertLockHeld(cs_wallet); // setLockedCoins
     setLockedCoins.insert(output);
 }
 
-void CWallet::UnlockCoin(COutPoint& output)
+void CWallet::UnlockCoin(const COutPoint& output)
 {
     AssertLockHeld(cs_wallet); // setLockedCoins
     setLockedCoins.erase(output);
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 96d5d4e1e0..b0781e917b 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -739,13 +739,14 @@ public:
      * Insert additional inputs into the transaction by
      * calling CreateTransaction();
      */
-    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nChangePosRet, std::string& strFailReason, bool includeWatching);
+    bool FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nChangePosInOut, std::string& strFailReason, bool includeWatching, const CTxDestination& destChange = CNoDestination());
 
     /**
      * Create a new transaction paying the recipients with a set of coins
      * selected by SelectCoins(); Also create the change output, when needed
+     * @note passing nChangePosInOut as -1 will result in setting a random position
      */
-    bool CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosRet,
+    bool CreateTransaction(const std::vector<CRecipient>& vecSend, CWalletTx& wtxNew, CReserveKey& reservekey, CAmount& nFeeRet, int& nChangePosInOut,
                            std::string& strFailReason, const CCoinControl *coinControl = NULL, bool sign = true);
     bool CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey);