From de25b1e3fe1d14c89881a5a64581b48a708a64a5 Mon Sep 17 00:00:00 2001
From: Patrick Nagurny <patrick@bitpay.com>
Date: Tue, 31 Jan 2017 13:30:25 -0500
Subject: [PATCH] reorg wip

---
 lib/services/db/reorg.js | 152 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 lib/services/db/reorg.js

diff --git a/lib/services/db/reorg.js b/lib/services/db/reorg.js
new file mode 100644
index 00000000..d27238a6
--- /dev/null
+++ b/lib/services/db/reorg.js
@@ -0,0 +1,152 @@
+'use strict';
+var index = require('../../');
+var bitcore = require('bitcore-lib');
+var BufferUtil = bitcore.util.buffer;
+var log = index.log;
+var async = require('async');
+
+function Reorg(node) {
+  this.node = node;
+  this.db = node.db;
+}
+
+Reorg.prototype.handleReorg = function(block, callback) {
+  var self = this;
+
+  self.findCommonAncestor(block, function(err, ancestorHash) {
+    if (err) {
+      return done(err);
+    }
+    log.warn('Reorg common ancestor found:', ancestorHash);
+    // Rewind the chain to the common ancestor
+    async.whilst(
+      function() {
+        // Wait until the tip equals the ancestor hash
+        return self.db.tip.hash !== ancestorHash;
+      },
+      function(removeDone) {
+
+        var concurrentTip = self.tip;
+
+        // TODO: expose prevHash as a string from bitcore
+        var prevHash = BufferUtil.reverse(tip.header.prevHash).toString('hex');
+
+        self.getBlock(prevHash, function(err, previousTip) {
+          if (err) {
+            removeDone(err);
+          }
+
+          // Undo the related indexes for this block
+          self.disconnectBlock(tip, function(err) {
+            if (err) {
+              return removeDone(err);
+            }
+
+            // Set the new tip
+            previousTip.__height = self.tip.__height - 1;
+            self.tip = previousTip;
+            self.emit('removeblock', tip);
+            removeDone();
+          });
+
+        });
+
+      },
+      callback
+    );
+  });
+};
+
+// Rewind concurrentTip to tip
+Reorg.prototype.rewindConcurrentTip = function(callback) {
+  
+};
+
+Reorg.prototype.findCommonAncestor = function(block, callback) {
+  var self = this;
+
+  var mainPosition = self.db.tip.hash;
+  var forkPosition = block.hash;
+
+  var mainHashesMap = {};
+  var forkHashesMap = {};
+
+  mainHashesMap[mainPosition] = true;
+  forkHashesMap[forkPosition] = true;
+
+  var commonAncestor = null;
+
+  async.whilst(
+    function() {
+      return !commonAncestor;
+    },
+    function(next) {
+      async.parallel(
+        [
+          function(next) {
+            if(!mainPosition) {
+              return next();
+            }
+
+            self.node.services.bitcoind.getBlockHeader(mainPosition, function(err, mainBlockHeader) {
+              if(err) {
+                return next(err);
+              }
+
+              if(mainBlockHeader && mainBlockHeader.prevHash) {
+                mainHashesMap[mainBlockHeader.prevHash] = true;
+                mainPosition = mainBlockHeader.prevHash;
+              } else {
+                mainPosition = null;
+              }
+
+              next();
+            });
+          },
+          function(next) {
+            if(!forkPosition) {
+              return next();
+            }
+
+            self.node.services.bitcoind.getBlockHeader(forkPosition, function(err, forkBlockHeader) {
+              if(err) {
+                return next(err);
+              }
+
+              if(forkBlockHeader && forkBlockHeader.prevHash) {
+                forkHashesMap[forkBlockHeader.prevHash] = true;
+                forkPosition = forkBlockHeader.prevHash;
+              } else {
+                forkPosition = null;
+              }
+
+              next();
+            });
+          }
+        ],
+        function(err) {
+          if(err) {
+            return next(err);
+          }
+
+          if(forkPosition && mainHashesMap[forkPosition]) {
+            commonAncestor = forkPosition;
+          }
+
+          if(mainPosition && forkHashesMap[mainPosition]) {
+            commonAncestor = mainPosition;
+          }
+
+          if(!mainPosition && !forkPosition) {
+            return next(new Error('Unknown common ancestor'));
+          }
+
+          next();
+        }
+      )
+    },
+    function(err) {
+      done(err, commonAncestor);
+    }
+  );
+};
\ No newline at end of file