From ee19c7fee60bfb9102f858be8539d64f7b834359 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Thu, 10 Nov 2016 18:13:31 -0800
Subject: [PATCH] chaindb: index all tips.

---
 lib/chain/browser.js |  6 ++++
 lib/chain/chaindb.js | 85 +++++++++++++++++++++++++++++++++++---------
 2 files changed, 75 insertions(+), 16 deletions(-)

diff --git a/lib/chain/browser.js b/lib/chain/browser.js
index 97ff74d7..ff6f7b3f 100644
--- a/lib/chain/browser.js
+++ b/lib/chain/browser.js
@@ -24,6 +24,9 @@ var layout = {
   n: function n(hash) {
     return 'n' + hex(hash);
   },
+  a: function a(hash) {
+    return 'a' + hex(hash);
+  },
   b: function b(hash) {
     return 'b' + hex(hash);
   },
@@ -52,6 +55,9 @@ var layout = {
 
     return 'C' + address + hex(hash) + pad32(index);
   },
+  aa: function aa(key) {
+    return key.slice(1, 65);
+  },
   Cc: function Cc(key) {
     var hash, index;
 
diff --git a/lib/chain/chaindb.js b/lib/chain/chaindb.js
index cb8353f5..b69a6fc0 100644
--- a/lib/chain/chaindb.js
+++ b/lib/chain/chaindb.js
@@ -36,6 +36,7 @@ var DUMMY = new Buffer([0]);
  *   h[hash] -> height
  *   H[height] -> hash
  *   n[hash] -> next hash
+ *   a[hash] -> tip index
  *   b[hash] -> block
  *   t[hash] -> extended tx
  *   c[hash] -> coins
@@ -61,6 +62,9 @@ var layout = {
   n: function n(hash) {
     return pair(0x6e, hash);
   },
+  a: function a(hash) {
+    return pair(0x61, hash);
+  },
   b: function b(hash) {
     return pair(0x62, hash);
   },
@@ -117,6 +121,9 @@ var layout = {
 
     return key;
   },
+  aa: function aa(key) {
+    return key.toString('hex', 1, 33);
+  },
   Cc: function Cc(key) {
     var hash, index;
 
@@ -660,6 +667,19 @@ ChainDB.prototype.getEntries = function getEntries() {
   });
 };
 
+/**
+ * Get all tip hashes.
+ * @returns {Promise} - Returns {@link Hash}[].
+ */
+
+ChainDB.prototype.getTips = function getTips() {
+  return this.db.keys({
+    gte: layout.a(constants.ZERO_HASH),
+    lte: layout.a(constants.MAX_HASH),
+    parse: layout.aa
+  });
+};
+
 /**
  * Get a coin (unspents only).
  * @param {Hash} hash
@@ -1209,23 +1229,34 @@ ChainDB.prototype.save = co(function* save(entry, block, view) {
 ChainDB.prototype._save = co(function* save(entry, block, view) {
   var hash = block.hash();
 
+  // Hash->height index
   this.put(layout.h(hash), U32(entry.height));
-  this.put(layout.e(hash), entry.toRaw());
 
+  // Entry data
+  this.put(layout.e(hash), entry.toRaw());
   this.cacheHash.push(entry.hash, entry);
 
+  // Tip index
+  this.del(layout.a(entry.prevBlock));
+  this.put(layout.a(hash), DUMMY);
+
   if (!view) {
+    // Save block data
     yield this.saveBlock(block);
     return;
   }
 
+  // Hash->next-block index
+  this.put(layout.n(entry.prevBlock), hash);
+
+  // Height->hash index
+  this.put(layout.H(entry.height), hash);
   this.cacheHeight.push(entry.height, entry);
 
-  this.put(layout.n(entry.prevBlock), hash);
-  this.put(layout.H(entry.height), hash);
-
+  // Connect block and save data
   yield this.saveBlock(block, view);
 
+  // New chain state
   this.put(layout.R, this.pending.commit(hash));
 });
 
@@ -1341,6 +1372,12 @@ ChainDB.prototype.reset = co(function* reset(block) {
   if (this.options.prune)
     throw new Error('Cannot reset when pruned.');
 
+  // We need to remove all alternate
+  // chains first. This is ugly, but
+  // it's the only safe way to reset
+  // the chain.
+  yield this.removeChains();
+
   tip = yield this.getTip();
   assert(tip);
 
@@ -1357,6 +1394,9 @@ ChainDB.prototype.reset = co(function* reset(block) {
 
     assert(!tip.isGenesis());
 
+    this.del(layout.a(tip.hash));
+    this.put(layout.a(tip.prevBlock), DUMMY);
+
     this.del(layout.H(tip.height));
     this.del(layout.h(tip.hash));
     this.del(layout.e(tip.hash));
@@ -1384,25 +1424,39 @@ ChainDB.prototype.reset = co(function* reset(block) {
 });
 
 /**
- * Remove an alternate chain.
- * @param {ChainEntry} tip
- * @param {ChainEntry} entry
+ * Remove all alternate chains.
  * @returns {Promise}
  */
 
-ChainDB.prototype.removeChain = co(function* removeChain(tip, entry) {
-  this.logger.debug('Removing alternate chain: %s->%s', tip.rhash, entry.rhash);
+ChainDB.prototype.removeChains = co(function* removeChains() {
+  var tips = yield this.getTips();
+  var i;
+
+  for (i = 0; i < tips.length; i++)
+    yield this.removeChain(tips[i]);
+});
+
+/**
+ * Remove an alternate chain.
+ * @param {Hash} hash - Alternate chain tip.
+ * @returns {Promise}
+ */
+
+ChainDB.prototype.removeChain = co(function* removeChain(hash) {
+  var tip = yield this.get(hash);
+
+  if (!tip)
+    throw new Error('Alternate chain tip not found.');
+
+  this.logger.debug('Removing alternate chain: %s.', tip.rhash);
 
   this.start();
 
-  for (;;) }
-    if (tip.hash === entry.hash)
+  while (tip) {
+    if (yield tip.isMainChain())
       break;
 
-    if (tip.isGenesis()) {
-      this.drop();
-      throw new Error('Target entry not in chain.');
-    }
+    assert(!tip.isGenesis());
 
     this.del(layout.h(tip.hash));
     this.del(layout.e(tip.hash));
@@ -1411,7 +1465,6 @@ ChainDB.prototype.removeChain = co(function* removeChain(tip, entry) {
     this.cacheHash.unpush(tip.hash);
 
     tip = yield this.get(tip.prevBlock);
-    assert(tip);
   }
 
   yield this.commit();