From 0a5fcad5e80c15450c6bacc9612c6cdf78803354 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Sun, 14 Aug 2016 16:46:49 -0700
Subject: [PATCH] keyring: add derive method.

---
 lib/bcoin/http/rpc.js | 13 +++++--------
 lib/bcoin/keyring.js  | 12 ++++++++++++
 lib/bcoin/wallet.js   |  3 +--
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/lib/bcoin/http/rpc.js b/lib/bcoin/http/rpc.js
index 4599f6d1..46d47b62 100644
--- a/lib/bcoin/http/rpc.js
+++ b/lib/bcoin/http/rpc.js
@@ -2577,8 +2577,7 @@ RPC.prototype.dumpprivkey = function dumpprivkey(args, callback) {
     if (!key)
       return callback(new RPCError('Wallet is locked.'));
 
-    key = key.deriveAccount44(ring.account);
-    key = key.derive(ring.change).derive(ring.index);
+    key = ring.derive(key);
 
     callback(null, key.toSecret());
   });
@@ -2620,8 +2619,7 @@ RPC.prototype.dumpwallet = function dumpwallet(args, callback) {
         if (!key)
           return callback(new RPCError('Wallet is locked.'));
 
-        key = key.deriveAccount44(ring.account);
-        key = key.derive(ring.change).derive(ring.index);
+        key = ring.derive(key);
         address = ring.getAddress('base58');
         fmt = '%s %s label= addr=%s';
 
@@ -3554,11 +3552,11 @@ RPC.prototype.signmessage = function signmessage(args, callback) {
   if (!address)
     return callback(new RPCError('Invalid address.'));
 
-  this.wallet.getKeyring(address, function(err, address) {
+  this.wallet.getKeyring(address, function(err, ring) {
     if (err)
       return callback(err);
 
-    if (!address)
+    if (!ring)
       return callback(new RPCError('Address not found.'));
 
     key = self.wallet.master.key;
@@ -3566,8 +3564,7 @@ RPC.prototype.signmessage = function signmessage(args, callback) {
     if (!key)
       return callback(new RPCError('Wallet is locked.'));
 
-    key = key.deriveAccount44(address.account);
-    key = key.derive(address.change).derive(address.index);
+    key = ring.derive(key);
 
     msg = new Buffer(RPC.magic + msg, 'utf8');
     msg = utils.hash256(msg);
diff --git a/lib/bcoin/keyring.js b/lib/bcoin/keyring.js
index 863e5570..0a24e68b 100644
--- a/lib/bcoin/keyring.js
+++ b/lib/bcoin/keyring.js
@@ -579,6 +579,18 @@ KeyRing.prototype.sign = function sign(tx, key, index, type) {
   return total;
 };
 
+/**
+ * Derive to address index.
+ * @param {HDPrivateKey} key
+ * @returns {HDPrivateKey}
+ */
+
+KeyRing.prototype.derive = function derive(key) {
+  if (key.isMaster())
+    key = key.deriveAccount44(this.account);
+  return key.derive(this.change).derive(this.index);
+};
+
 KeyRing.prototype.__defineGetter__('publicKey', function() {
   return this.getPublicKey();
 });
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 7dec14a7..3a6144c0 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -1350,8 +1350,7 @@ Wallet.sign = function sign(addresses, master, tx, index, type) {
 
   for (i = 0; i < addresses.length; i++) {
     address = addresses[i];
-    key = master.deriveAccount44(address.account);
-    key = key.derive(address.change).derive(address.index);
+    key = address.derive(master);
     assert(utils.equal(key.getPublicKey(), address.key));
     total += address.sign(tx, key, index, type);
   }