From 82e2255ba1f419943f5fb19130fc0c4563d581c0 Mon Sep 17 00:00:00 2001
From: Ismael Bejarano <ismaelbej@gmail.com>
Date: Fri, 27 Mar 2020 16:04:29 -0300
Subject: [PATCH] Add notification of new block using websockets

---
 src/app.js          | 19 +++++++++++++++----
 src/config.js       |  2 +-
 src/lib/ethereum.js | 12 +++++++++++-
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/app.js b/src/app.js
index ce200fb..2f2532e 100644
--- a/src/app.js
+++ b/src/app.js
@@ -2,9 +2,10 @@ import express from 'express';
 import logger from 'morgan';
 import cors from 'cors';
 import http from 'http';
+import socketIo from 'socket.io';
 import api from './routes/api';
-import { initialize as initializeContracts } from './controllers/Contracts';
-import { initialize as initializeEthereum } from './lib/ethereum';
+import contracts from './controllers/Contracts';
+import ethereum from './lib/ethereum';
 
 export function createApp() {
   const app = express();
@@ -37,9 +38,19 @@ export function createApp() {
 }
 
 export async function createServer(app, config) {
-  await initializeContracts(config);
-  await initializeEthereum(config);
+  await contracts.initialize(config);
+  const eventEmitter = await ethereum.initialize(config);
   const server = http.createServer(app);
+  const io = socketIo(server);
+  io.on('connect', (socket) => {
+    console.log('New client', socket.id);
+    eventEmitter.on('newBlock', (block) => {
+      socket.emit('newBlock', block.number);
+    });
+    socket.on('disconnect', () => {
+      console.log('Client disconnected', socket.id);
+    });
+  });
   server.listen(config.port || 5000);
   return server;
 }
diff --git a/src/config.js b/src/config.js
index 1ff383c..cc79e6e 100644
--- a/src/config.js
+++ b/src/config.js
@@ -1,4 +1,4 @@
 export default {
   port: 5000,
-  rpcnode: 'http://localhost:8545',
+  rpcnode: 'ws://localhost:8545',
 };
diff --git a/src/lib/ethereum.js b/src/lib/ethereum.js
index 94f7d51..8ecdcee 100644
--- a/src/lib/ethereum.js
+++ b/src/lib/ethereum.js
@@ -1,6 +1,9 @@
+import EventEmitter from 'events';
 import Web3 from 'web3';
 import LRU from 'lru-cache';
 
+class EthereumEmitter extends EventEmitter {}
+
 const web3 = new Web3();
 
 export const getBalance = web3.eth.getBalance;
@@ -37,8 +40,15 @@ export function initialize(config) {
   if (typeof config.web3provider !== 'undefined') {
     web3.setProvider(config.web3provider);
   } else {
-    web3.setProvider(new Web3.providers.HttpProvider(config.rpcnode || 'http://localhost:8545'));
+    web3.setProvider(new Web3.providers.WebsocketProvider(config.rpcnode || 'ws://localhost:8545'));
   }
+  const eventEmitter = new EthereumEmitter();
+  web3.eth.subscribe('newBlockHeaders', (err, result) => {
+    if (!err) {
+      eventEmitter.emit('newBlock', result);
+    }
+  });
+  return eventEmitter;
 }
 
 // Can query by number or hash, but only cache by hash