From 29be8085e3609148885fd2a1b5434a3bf784090b Mon Sep 17 00:00:00 2001
From: Mathias Buus <mathiasbuus@gmail.com>
Date: Mon, 3 Oct 2016 16:42:16 +0200
Subject: [PATCH] refactor query-stream

---
 query-stream.js | 119 +++++++++++++++++++++++++++---------------------
 1 file changed, 68 insertions(+), 51 deletions(-)

diff --git a/query-stream.js b/query-stream.js
index 611ac08..3885744 100644
--- a/query-stream.js
+++ b/query-stream.js
@@ -23,14 +23,16 @@ function QueryStream (dht, query, opts) {
   this.destroyed = false
   this.responses = 0
   this.errors = 0
+  this.closest = []
 
+  this._post = opts.post
   this._dht = dht
   this._bootstrapped = false
   this._concurrency = opts.concurrency
   this._inflight = 0
   this._k = 20
   this._onresponse = onresponse
-  this.closest = []
+  this._pending = []
 
   function onresponse (err, response, peer) {
     self._update(err, response, peer)
@@ -53,7 +55,8 @@ QueryStream.prototype._bootstrap = function () {
   var bootstrap = this._dht.nodes.closest(this.target, this._k)
 
   for (var i = 0; i < bootstrap.length; i++) {
-    this._add(bootstrap[i])
+    var b = bootstrap[i]
+    this._addPending({id: b.id, port: b.port, host: b.host})
   }
 
   if (bootstrap.length < this._dht.bootstrap.length) {
@@ -71,31 +74,23 @@ QueryStream.prototype._update = function (err, res, peer) {
     this.errors++
     this.emit('warning', err)
     if (this._readableState.flowing === true) this._read()
-  } else {
-    this.responses++
-
-    if (res.id) {
-      var prev = this._get(res.id)
-      if (prev) prev.roundtripToken = res.roundtripToken
-    }
+    return
+  }
 
-    // TODO: do not add nodes to table.
-    // instead merge-sort with table so we only add nodes that actually respond
-    var n = decodeNodes(res.nodes)
+  this.responses++
+  this._addClosest(res, peer)
 
-    for (var i = 0; i < n.length; i++) {
-      if (!bufferEquals(n[i].id, this._dht.id)) this._add(n[i])
-    }
+  var candidates = decodeNodes(res.nodes)
+  for (var i = 0; i < candidates.length; i++) this._addPending(candidates[i])
 
-    this.push({
-      node: {
-        id: res.id,
-        port: peer.port,
-        host: peer.host
-      },
-      value: res.value
-    })
-  }
+  this.push({
+    node: {
+      id: res.id,
+      port: peer.port,
+      host: peer.host
+    },
+    value: res.value
+  })
 }
 
 QueryStream.prototype._read = function () {
@@ -106,10 +101,10 @@ QueryStream.prototype._read = function () {
   if (!free && !this._inflight) free = 1
   var missing = free
 
-  for (var i = 0; missing && i < this.closest.length; i++) {
-    if (this.closest[i].queried) continue
+  for (var i = 0; missing && i < this._pending.length; i++) {
+    if (this._pending[i].queried) continue
     missing--
-    this._send(this.closest[i], false)
+    this._send(this._pending[i], false)
   }
 
   if (!this._inflight && free) {
@@ -118,40 +113,36 @@ QueryStream.prototype._read = function () {
 }
 
 QueryStream.prototype._send = function (node, bootstrap) {
-  if (!bootstrap && node.queried) return
-  if (!bootstrap) node.queried = true
+  if (!bootstrap) {
+    if (node.queried) return
+    node.queried = true
+  }
   this._inflight++
   this._dht._request(this.request, node, false, this._onresponse)
 }
 
-QueryStream.prototype._get = function (id) {
-  for (var i = 0; i < this.closest.length; i++) {
-    if (bufferEquals(this.closest[i].id, id)) return this.closest[i]
-  }
-  return null
+QueryStream.prototype._addPending = function (node) {
+  if (bufferEquals(node.id, this._dht.id)) return
+  node.distance = xor(this.target, node.id)
+  insertSorted(node, this._k, this._pending)
 }
 
-QueryStream.prototype._add = function (node) {
-  if (this._get(node.id)) return
+QueryStream.prototype._addClosest = function (res, peer) {
+  if (!res.id || !res.roundtripToken || bufferEquals(res.id, this._dht.id)) return
 
-  node.distance = xor(this.target, node.id)
-  node.queried = false
+  var prev = getNode(res.id, this._pending)
 
-  if (this.closest.length < this._k) {
-    this.closest.push(node)
-    return
+  if (!prev) {
+    prev = {
+      id: res.id,
+      port: peer.port,
+      host: peer.host,
+      distance: xor(res.id, this.target)
+    }
   }
 
-  if (!xor.gt(this.closest[this._k - 1].distance, node.distance)) return
-
-  this.closest[this._k - 1] = node
-
-  var pos = this._k - 1
-  while (pos && xor.gt(this.closest[pos - 1].distance, node.distance)) {
-    this.closest[pos] = this.closest[pos - 1]
-    this.closest[pos - 1] = node
-    pos--
-  }
+  prev.roundtripToken = res.roundtripToken
+  insertSorted(prev, this._k, this.closest)
 }
 
 function decodeNodes (buf) {
@@ -162,3 +153,29 @@ function decodeNodes (buf) {
     return []
   }
 }
+
+function getNode (id, list) {
+  // find id in the list.
+  // technically this would be faster with binary search (against distance)
+  // but this list is always small, so meh
+  for (var i = 0; i < list.length; i++) {
+    if (bufferEquals(list[i].id, id)) return list[i]
+  }
+
+  return null
+}
+
+function insertSorted (node, max, list) {
+  if (list.length === max && !xor.lt(node.distance, list[max - 1].distance)) return
+  if (getNode(node.id, list)) return
+
+  if (list.length < max) list.push(node)
+  else list[max - 1] = node
+
+  var pos = list.length - 1
+  while (pos && xor.gt(list[pos - 1].distance, node.distance)) {
+    list[pos] = list[pos - 1]
+    list[pos - 1] = node
+    pos--
+  }
+}