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, 46 insertions, 15 deletions

diff --git a/src/rpcwallet.cpp b/src/rpcwallet.cpp
index d097b6a0fa..142487bc8c 100644
--- a/src/rpcwallet.cpp
+++ b/src/rpcwallet.cpp
@@ -317,7 +317,7 @@ Value getaddressesbyaccount(const Array& params, bool fHelp)
     return ret;
 }
 
-static void SendMoney(const CTxDestination &address, CAmount nValue, CWalletTx& wtxNew)
+static void SendMoney(const CTxDestination &address, CAmount nValue, bool fSubtractFeeFromAmount, CWalletTx& wtxNew)
 {
     CAmount curBalance = pwalletMain->GetBalance();
 
@@ -335,11 +335,14 @@ static void SendMoney(const CTxDestination &address, CAmount nValue, CWalletTx&
     CReserveKey reservekey(pwalletMain);
     CAmount nFeeRequired;
     std::string strError;
-    if (!pwalletMain->CreateTransaction(scriptPubKey, nValue, wtxNew, reservekey, nFeeRequired, strError)) {
-        if (nValue + nFeeRequired > curBalance)
-            throw JSONRPCError(RPC_WALLET_ERROR, strprintf("Error: This transaction requires a transaction fee of at least %s because of its amount, complexity, or use of recently received funds!", FormatMoney(nFeeRequired)));
-        else
-            throw JSONRPCError(RPC_WALLET_ERROR, strError);
+    vector<CRecipient> vecSend;
+    int nChangePosRet = -1;
+    CRecipient recipient = {scriptPubKey, nValue, fSubtractFeeFromAmount};
+    vecSend.push_back(recipient);
+    if (!pwalletMain->CreateTransaction(vecSend, wtxNew, reservekey, nFeeRequired, nChangePosRet, strError)) {
+        if (!fSubtractFeeFromAmount && nValue + nFeeRequired > pwalletMain->GetBalance())
+            strError = strprintf("Error: This transaction requires a transaction fee of at least %s because of its amount, complexity, or use of recently received funds!", FormatMoney(nFeeRequired));
+        throw JSONRPCError(RPC_WALLET_ERROR, strError);
     }
     if (!pwalletMain->CommitTransaction(wtxNew, reservekey))
         throw JSONRPCError(RPC_WALLET_ERROR, "Error: The transaction was rejected! This might happen if some of the coins in your wallet were already spent, such as if you used a copy of wallet.dat and coins were spent in the copy but not marked as spent here.");
@@ -347,9 +350,9 @@ static void SendMoney(const CTxDestination &address, CAmount nValue, CWalletTx&
 
 Value sendtoaddress(const Array& params, bool fHelp)
 {
-    if (fHelp || params.size() < 2 || params.size() > 4)
+    if (fHelp || params.size() < 2 || params.size() > 5)
         throw runtime_error(
-            "sendtoaddress \"bitcoinaddress\" amount ( \"comment\" \"comment-to\" )\n"
+            "sendtoaddress \"bitcoinaddress\" amount ( \"comment\" \"comment-to\" subtractfeefromamount )\n"
             "\nSend an amount to a given address. The amount is a real and is rounded to the nearest 0.00000001\n"
             + HelpRequiringPassphrase() +
             "\nArguments:\n"
@@ -360,11 +363,14 @@ Value sendtoaddress(const Array& params, bool fHelp)
             "4. \"comment-to\"  (string, optional) A comment to store the name of the person or organization \n"
             "                             to which you're sending the transaction. This is not part of the \n"
             "                             transaction, just kept in your wallet.\n"
+            "5. subtractfeefromamount  (boolean, optional, default=false) The fee will be deducted from the amount being sent.\n"
+            "                             The recipient will receive less bitcoins than you enter in the amount field.\n"
             "\nResult:\n"
             "\"transactionid\"  (string) The transaction id.\n"
             "\nExamples:\n"
             + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1")
             + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1 \"donation\" \"seans outpost\"")
+            + HelpExampleCli("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\" 0.1 \"\" \"\" true")
             + HelpExampleRpc("sendtoaddress", "\"1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd\", 0.1, \"donation\", \"seans outpost\"")
         );
 
@@ -384,9 +390,13 @@ Value sendtoaddress(const Array& params, bool fHelp)
     if (params.size() > 3 && params[3].type() != null_type && !params[3].get_str().empty())
         wtx.mapValue["to"]      = params[3].get_str();
 
+    bool fSubtractFeeFromAmount = false;
+    if (params.size() > 4)
+        fSubtractFeeFromAmount = params[4].get_bool();
+
     EnsureWalletIsUnlocked();
 
-    SendMoney(address.Get(), nAmount, wtx);
+    SendMoney(address.Get(), nAmount, fSubtractFeeFromAmount, wtx);
 
     return wtx.GetHash().GetHex();
 }
@@ -840,7 +850,7 @@ Value sendfrom(const Array& params, bool fHelp)
     if (nAmount > nBalance)
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Account has insufficient funds");
 
-    SendMoney(address.Get(), nAmount, wtx);
+    SendMoney(address.Get(), nAmount, false, wtx);
 
     return wtx.GetHash().GetHex();
 }
@@ -848,9 +858,9 @@ Value sendfrom(const Array& params, bool fHelp)
 
 Value sendmany(const Array& params, bool fHelp)
 {
-    if (fHelp || params.size() < 2 || params.size() > 4)
+    if (fHelp || params.size() < 2 || params.size() > 5)
         throw runtime_error(
-            "sendmany \"fromaccount\" {\"address\":amount,...} ( minconf \"comment\" )\n"
+            "sendmany \"fromaccount\" {\"address\":amount,...} ( minconf \"comment\" {\"address\":true,...} )\n"
             "\nSend multiple times. Amounts are double-precision floating point numbers."
             + HelpRequiringPassphrase() + "\n"
             "\nArguments:\n"
@@ -862,6 +872,14 @@ Value sendmany(const Array& params, bool fHelp)
             "    }\n"
             "3. minconf                 (numeric, optional, default=1) Only use the balance confirmed at least this many times.\n"
             "4. \"comment\"             (string, optional) A comment\n"
+            "5. subtractfeefromamount   (string, optional) A json object with addresses and booleans.\n"
+            "                           The fee will be equally deducted from the amount of each selected address.\n"
+            "                           Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
+            "                           Default for each address is false. If no addresses are specified here, the sender pays the fee.\n"
+            "    {\n"
+            "      \"address\":true     (boolean) Subtract fee from this address\n"
+            "      ,...\n"
+            "    }\n"
             "\nResult:\n"
             "\"transactionid\"          (string) The transaction id for the send. Only 1 transaction is created regardless of \n"
             "                                    the number of addresses.\n"
@@ -870,6 +888,8 @@ Value sendmany(const Array& params, bool fHelp)
             + HelpExampleCli("sendmany", "\"\" \"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\\\":0.01,\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\"") +
             "\nSend two amounts to two different addresses setting the confirmation and comment:\n"
             + HelpExampleCli("sendmany", "\"\" \"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\\\":0.01,\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\" 6 \"testing\"") +
+            "\nSend two amounts to two different addresses, subtract fee from amount:\n"
+            + HelpExampleCli("sendmany", "\"\" \"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\\\":0.01,\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\" 1 \"\" \"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\\\":true,\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":true}\"") +
             "\nAs a json rpc call\n"
             + HelpExampleRpc("sendmany", "\"\", \"{\\\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XZ\\\":0.01,\\\"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz\\\":0.02}\", 6, \"testing\"")
         );
@@ -887,8 +907,12 @@ Value sendmany(const Array& params, bool fHelp)
     if (params.size() > 3 && params[3].type() != null_type && !params[3].get_str().empty())
         wtx.mapValue["comment"] = params[3].get_str();
 
+    Object subtractFeeFromAmount;
+    if (params.size() > 4)
+        subtractFeeFromAmount = params[4].get_obj();
+
     set<CBitcoinAddress> setAddress;
-    vector<pair<CScript, CAmount> > vecSend;
+    vector<CRecipient> vecSend;
 
     CAmount totalAmount = 0;
     BOOST_FOREACH(const Pair& s, sendTo)
@@ -905,7 +929,13 @@ Value sendmany(const Array& params, bool fHelp)
         CAmount nAmount = AmountFromValue(s.value_);
         totalAmount += nAmount;
 
-        vecSend.push_back(make_pair(scriptPubKey, nAmount));
+        bool fSubtractFeeFromAmount = false;
+        BOOST_FOREACH(const Pair& s2, subtractFeeFromAmount)
+            if (s2.name_ == s.name_ && s2.value_.get_bool() == true)
+                fSubtractFeeFromAmount = true;
+
+        CRecipient recipient = {scriptPubKey, nAmount, fSubtractFeeFromAmount};
+        vecSend.push_back(recipient);
     }
 
     EnsureWalletIsUnlocked();
@@ -918,8 +948,9 @@ Value sendmany(const Array& params, bool fHelp)
     // Send
     CReserveKey keyChange(pwalletMain);
     CAmount nFeeRequired = 0;
+    int nChangePosRet = -1;
     string strFailReason;
-    bool fCreated = pwalletMain->CreateTransaction(vecSend, wtx, keyChange, nFeeRequired, strFailReason);
+    bool fCreated = pwalletMain->CreateTransaction(vecSend, wtx, keyChange, nFeeRequired, nChangePosRet, strFailReason);
     if (!fCreated)
         throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, strFailReason);
     if (!pwalletMain->CommitTransaction(wtx, keyChange))