From f1f5a2e5d38c803e7cd904764fe5d1facf213e62 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Wed, 2 Nov 2016 17:08:15 -0700
Subject: [PATCH] account: remove change lookahead.

---
 lib/wallet/account.js | 40 +++++++++++++++-------------------------
 1 file changed, 15 insertions(+), 25 deletions(-)

diff --git a/lib/wallet/account.js b/lib/wallet/account.js
index 79c1f864..5e8dcb45 100644
--- a/lib/wallet/account.js
+++ b/lib/wallet/account.js
@@ -452,9 +452,9 @@ Account.prototype.createKey = co(function* createKey(branch) {
       this.receive = key;
       break;
     case 1:
+      // Note: no lookahead here.
       key = this.deriveChange(this.changeDepth);
-      lookahead = this.deriveChange(this.changeDepth + this.lookahead);
-      yield this.saveKey(lookahead);
+      yield this.saveKey(key);
       this.changeDepth++;
       this.change = key;
       break;
@@ -626,7 +626,13 @@ Account.prototype.initDepth = co(function* initDepth() {
 
   yield this.saveKey(this.receive);
 
-  // Change Address
+  // Lookahead
+  for (i = 0; i < this.lookahead; i++) {
+    key = this.deriveReceive(i + 1);
+    yield this.saveKey(key);
+  }
+
+  // Change Address (no lookahead)
   this.change = this.deriveChange(0);
   this.changeDepth = 1;
 
@@ -638,20 +644,8 @@ Account.prototype.initDepth = co(function* initDepth() {
     this.nestedDepth = 1;
 
     yield this.saveKey(this.nested);
-  }
 
-  // Lookaheads
-  for (i = 0; i < this.lookahead; i++) {
-    key = this.deriveReceive(i + 1);
-    yield this.saveKey(key);
-  }
-
-  for (i = 0; i < this.lookahead; i++) {
-    key = this.deriveChange(i + 1);
-    yield this.saveKey(key);
-  }
-
-  if (this.witness) {
+    // Lookahead
     for (i = 0; i < this.lookahead; i++) {
       key = this.deriveNested(i + 1);
       yield this.saveKey(key);
@@ -677,7 +671,7 @@ Account.prototype.syncDepth = co(function* syncDepth(receive, change, nested) {
   if (receive > this.receiveDepth) {
     depth = this.receiveDepth + this.lookahead;
 
-    assert(receive <= depth);
+    assert(this.lookahead === 0 || receive <= depth);
 
     for (i = depth; i < receive + this.lookahead; i++) {
       key = this.deriveReceive(i);
@@ -692,14 +686,10 @@ Account.prototype.syncDepth = co(function* syncDepth(receive, change, nested) {
   }
 
   if (change > this.changeDepth) {
-    depth = this.changeDepth + this.lookahead;
+    assert(change === this.changeDepth + 1);
 
-    assert(change <= depth);
-
-    for (i = depth; i < change + this.lookahead; i++) {
-      key = this.deriveChange(i);
-      yield this.saveKey(key);
-    }
+    key = this.deriveChange(change - 1);
+    yield this.saveKey(key);
 
     this.change = this.deriveChange(change - 1);
     this.changeDepth = change;
@@ -710,7 +700,7 @@ Account.prototype.syncDepth = co(function* syncDepth(receive, change, nested) {
   if (this.witness && nested > this.nestedDepth) {
     depth = this.nestedDepth + this.lookahead;
 
-    assert(nested <= depth);
+    assert(this.lookahead === 0 || nested <= depth);
 
     for (i = depth; i < nested + this.lookahead; i++) {
       key = this.deriveNested(i);