From 902bbd1111eeef273e393375a155b7abc303da47 Mon Sep 17 00:00:00 2001
From: Josh Rickmar <jrick@conformal.com>
Date: Tue, 8 Apr 2014 17:49:02 -0500
Subject: [PATCH] Report correct change address after composing txs.

---
 createtx.go  | 27 ++++++++++-----------------
 rpcserver.go |  7 ++-----
 2 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/createtx.go b/createtx.go
index d08a4ed..e4e3c97 100644
--- a/createtx.go
+++ b/createtx.go
@@ -61,10 +61,9 @@ var TxFeeIncrement = struct {
 }
 
 type CreatedTx struct {
-	tx        *btcutil.Tx
-	time      time.Time
-	haschange bool
-	changeIdx uint32
+	tx         *btcutil.Tx
+	time       time.Time
+	changeAddr btcutil.Address
 }
 
 // ByAmount defines the methods needed to satisify sort.Interface to
@@ -185,14 +184,11 @@ func (a *Account) txToPairs(pairs map[string]int64, minconf int) (*CreatedTx, er
 	// a higher fee if not enough was originally chosen.
 	txNoInputs := msgtx.Copy()
 
+	var selectedInputs []*tx.RecvTxOut
 	// These are nil/zeroed until a change address is needed, and reused
 	// again in case a change utxo has already been chosen.
 	var changeAddr btcutil.Address
 
-	var selectedInputs []*tx.RecvTxOut
-	hasChange := false
-	changeIndex := uint32(0)
-
 	// Get the number of satoshis to increment fee by when searching for
 	// the minimum tx fee needed.
 	fee := int64(0)
@@ -209,13 +205,11 @@ func (a *Account) txToPairs(pairs map[string]int64, minconf int) (*CreatedTx, er
 
 		// Check if there are leftover unspent outputs, and return coins back to
 		// a new address we own.
+		//
+		// TODO: change needs to be inserted into a random txout index, or else
+		// this is a privacy risk.
 		change := btcin - amt - fee
 		if change > 0 {
-			hasChange = true
-			// TODO: this needs to be randomly inserted into the
-			// tx, or else this is a privacy risk
-			changeIndex = 0
-
 			// Get a new change address if one has not already been found.
 			if changeAddr == nil {
 				changeAddr, err = a.ChangeAddress(&bs, cfg.KeypoolSize)
@@ -301,10 +295,9 @@ func (a *Account) txToPairs(pairs map[string]int64, minconf int) (*CreatedTx, er
 	buf := new(bytes.Buffer)
 	msgtx.BtcEncode(buf, btcwire.ProtocolVersion)
 	info := &CreatedTx{
-		tx:        btcutil.NewTx(msgtx),
-		time:      time.Now(),
-		haschange: hasChange,
-		changeIdx: changeIndex,
+		tx:         btcutil.NewTx(msgtx),
+		time:       time.Now(),
+		changeAddr: changeAddr,
 	}
 	return info, nil
 }
diff --git a/rpcserver.go b/rpcserver.go
index f667929..49f74a5 100644
--- a/rpcserver.go
+++ b/rpcserver.go
@@ -1316,10 +1316,7 @@ func sendPairs(icmd btcjson.Cmd, account string, amounts map[string]int64,
 
 	// If a change address was added, sync wallet to disk and request
 	// transaction notifications to the change address.
-	if createdTx.haschange {
-		script := createdTx.tx.MsgTx().TxOut[createdTx.changeIdx].PkScript
-		_, addrs, _, _ := btcscript.ExtractPkScriptAddrs(script, cfg.Net())
-
+	if createdTx.changeAddr != nil {
 		AcctMgr.ds.ScheduleWalletWrite(a)
 		if err := AcctMgr.ds.FlushAccount(a); err != nil {
 			e := btcjson.Error{
@@ -1328,7 +1325,7 @@ func sendPairs(icmd btcjson.Cmd, account string, amounts map[string]int64,
 			}
 			return nil, &e
 		}
-		a.ReqNewTxsForAddress(addrs[0])
+		a.ReqNewTxsForAddress(createdTx.changeAddr)
 	}
 
 	serializedTx := new(bytes.Buffer)