From 2122b0102356dc5be08f970821434b3e54bfda0a Mon Sep 17 00:00:00 2001
From: Rob Riddle <rob@bitpay.com>
Date: Fri, 18 Aug 2017 15:22:47 -0400
Subject: [PATCH] Use transform stream instead of async for /blocks

---
 lib/blocks.js | 70 +++++++++++++++++++++++++++------------------------
 package.json  |  1 +
 2 files changed, 38 insertions(+), 33 deletions(-)

diff --git a/lib/blocks.js b/lib/blocks.js
index 42e1018..2fb96fe 100644
--- a/lib/blocks.js
+++ b/lib/blocks.js
@@ -1,5 +1,8 @@
 'use strict';
 
+var Stream = require('stream');
+var util = require('util');
+
 var async = require('async');
 var bitcore = require('bitcore-lib');
 var _ = bitcore.deps._;
@@ -8,6 +11,7 @@ var BN = bitcore.crypto.BN;
 var LRU = require('lru-cache');
 var Common = require('./common');
 var bcoin = require('bcoin');
+var JsonStream = require('JSONStream');
 
 function BlockController(options) {
   var self = this;
@@ -269,6 +273,16 @@ BlockController.prototype.list = function(req, res) {
       return self.common.handleErrors(err, res);
     }
 
+    function BlockBuilder() {
+      Stream.Transform.call(this, {objectMode: true});
+    }
+
+    util.inherits(BlockBuilder, Stream.Transform);
+
+    BlockBuilder.prototype._transform = function transformObject(hash, encoding, done) {
+      self._getBlockSummary(hash, moreTimestamp, done);
+    };
+
     hashes.reverse();
 
     if(hashes.length > limit) {
@@ -276,40 +290,30 @@ BlockController.prototype.list = function(req, res) {
       hashes = hashes.slice(0, limit);
     }
 
-    async.mapSeries(
-      hashes,
-      function(hash, next) {
-        self._getBlockSummary(hash, moreTimestamp, next);
-      },
-      function(err, blocks) {
-        if(err) {
-          return self.common.handleErrors(err, res);
-        }
-
-        blocks.sort(function(a, b) {
-          return b.height - a.height;
-        });
-
-        var data = {
-          blocks: blocks,
-          length: blocks.length,
-          pagination: {
-            next: next,
-            prev: prev,
-            currentTs: lte - 1,
-            current: dateStr,
-            isToday: isToday,
-            more: more
-          }
-        };
-
-        if(more) {
-          data.pagination.moreTs = moreTimestamp;
-        }
-
-        res.jsonp(data);
+    var data = JSON.stringify({
+      length: hashes.length,
+      pagination: {
+        next: next,
+        prev: prev,
+        currentTs: lte - 1,
+        current: dateStr,
+        isToday: isToday,
+        more: more,
+        moreTs: more ? moreTimestamp : undefined
       }
-    );
+    });
+
+    var readableStream = new Stream.Readable({objectMode: true});
+    var blockBuilder = new BlockBuilder();
+    readableStream
+      .pipe(blockBuilder)
+      .pipe(JsonStream.stringify('{"blocks":[', ',', '],' + data.substr(1)))
+      .pipe(res);
+
+    hashes.forEach(function(hash) {
+      readableStream.push(hash);
+    });
+    readableStream.push(null);
   });
 };
 
diff --git a/package.json b/package.json
index 50d51b6..f2124ca 100644
--- a/package.json
+++ b/package.json
@@ -60,6 +60,7 @@
   "main": "lib",
   "bitcoreNode": "lib",
   "dependencies": {
+    "JSONStream": "^1.3.1",
     "async": "*",
     "bcoin": "bcoin-org/bcoin#886008a1822ce1da7fa8395ee7db4bcc1750a28a",
     "bitcore-lib": "bitpay/bitcore-lib#transitional",