From 4415f978a6319f974caba7aefc8b91e909ea5db6 Mon Sep 17 00:00:00 2001
From: Fedor Indutny <fedor@indutny.com>
Date: Sat, 10 May 2014 22:31:51 +0400
Subject: [PATCH] chain: kill forks :)

---
 lib/bcoin/chain.js | 52 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index 839a8c39..edcf3522 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -105,7 +105,7 @@ Chain.prototype._probeIndex = function _probeIndex(hash, ts) {
 
   for (var i = start; i <= end; i++)
     if (this.index.hashes[i] === hash)
-      return { height: this.index.heights[i], ts: this.index.ts[i] };
+      return { i: i, height: this.index.heights[i], ts: this.index.ts[i] };
 
   return false;
 };
@@ -139,6 +139,52 @@ Chain.prototype._addIndex = function _addIndex(hash, ts, height) {
   });
 };
 
+Chain.prototype._killFork = function _killFork(probe) {
+  var delta = 2 * 3600;
+  var upper = probe.ts + delta;
+  var lower = probe.ts - delta;
+
+  // Search duplicate heights down
+  var index = -1;
+  for (var i = probe.i - 1; i > 0 && this.index.ts[i] > lower; i--) {
+    if (probe.height === this.index.heights[i]) {
+      index = i;
+      break;
+    }
+  }
+
+  // And up
+  if (index === -1) {
+    var len = this.index.ts.length;
+    for (var i = probe.i + 1; i < len && this.index.ts[i] < upper; i++) {
+      if (probe.height === this.index.heights[i]) {
+        index = i;
+        break;
+      }
+    }
+  }
+
+  if (index === -1)
+    return false;
+
+  var hash = this.index.hashes[index];
+  this.index.hashes.splice(index, 1);
+  this.index.ts.splice(index, 1);
+  this.index.heights.splice(index, 1);
+
+  // Delete both blocks, let's see what others will choose
+  if (!this.storage)
+    return true;
+
+  var self = this;
+  this.storage.del(this.prefix + hash, obj, function(err) {
+    if (err)
+      self.emit('error', err);
+  });
+
+  return true;
+};
+
 Chain.prototype.add = function add(block) {
   if (this.loading) {
     this.once('load', function() {
@@ -163,6 +209,10 @@ Chain.prototype.add = function add(block) {
 
     var prevProbe = this._probeIndex(prev, block.ts);
 
+    // Remove forked nodes from storage, if shorter chain is detected
+    if (this._killFork(prevProbe))
+      break;
+
     // If previous block wasn't ever seen - add current to orphans
     if (!this._probeIndex(hash, block.ts) && !prevProbe) {
       this.orphan.count++;