Complete PubSub

average-work.js

@@ -0,0 +1,26 @@
+const Blockchain = require('./blockchain');
+
+const blockchain = new Blockchain();
+
+blockchain.addBlock({ data: 'initial' });
+
+console.log('first block', blockchain.chain[blockchain.chain.length-1]);
+
+let prevTimestamp, nextTimestamp, nextBlock, timeDiff, average;
+
+const times = [];
+
+for (let i=0; i<10000; i++) {
+  prevTimestamp = blockchain.chain[blockchain.chain.length-1].timestamp;
+
+  blockchain.addBlock({ data: `block ${i}`});
+  nextBlock = blockchain.chain[blockchain.chain.length-1];
+
+  nextTimestamp = nextBlock.timestamp;
+  timeDiff = nextTimestamp - prevTimestamp;
+  times.push(timeDiff);
+
+  average = times.reduce((total, num) => (total + num))/times.length;
+
+  console.log(`Time to mine block: ${timeDiff}ms. Difficulty: ${nextBlock.difficulty}. Average time: ${average}ms`);
+}

block.js

@@ -1,3 +1,4 @@
+const hexToBinary = require('hex-to-binary');
 const { GENESIS_DATA, MINE_RATE } = require('./config');
 const cryptoHash = require('./crypto-hash');
 
@@ -26,7 +27,7 @@ class Block {
       timestamp = Date.now();
       difficulty = Block.adjustDifficulty({ originalBlock: lastBlock, timestamp });
       hash = cryptoHash(timestamp, lastHash, data, nonce, difficulty);
-    } while (hash.substring(0, difficulty) !== '0'.repeat(difficulty));
+    } while (hexToBinary(hash).substring(0, difficulty) !== '0'.repeat(difficulty));
 
     return new this({ timestamp, lastHash, data, difficulty, nonce, hash });
   }

block.test.js

@@ -1,3 +1,4 @@
+const hexToBinary = require('hex-to-binary');
 const Block = require('./block');
 const { GENESIS_DATA, MINE_RATE } = require('./config');
 const cryptoHash = require('./crypto-hash');
@@ -67,7 +68,7 @@ describe('Block', () => {
     });
 
     it('sets a `hash` that matches the difficulty criteria', () => {
-      expect(minedBlock.hash.substring(0, minedBlock.difficulty))
+      expect(hexToBinary(minedBlock.hash).substring(0, minedBlock.difficulty))
         .toEqual('0'.repeat(minedBlock.difficulty));
     });
 

blockchain.js

@@ -37,14 +37,16 @@ class Blockchain {
 
     for (let i=1; i<chain.length; i++) {
       const { timestamp, lastHash, hash, nonce, difficulty, data } = chain[i];
-
       const actualLastHash = chain[i-1].hash;
+      const lastDifficulty = chain[i-1].difficulty;
 
       if (lastHash !== actualLastHash) return false;
 
       const validatedHash = cryptoHash(timestamp, lastHash, data, nonce, difficulty);
 
       if (hash !== validatedHash) return false;
+
+      if (Math.abs(lastDifficulty - difficulty) > 1) return false;
     }
 
     return true;

blockchain.test.js

@@ -1,5 +1,6 @@
 const Blockchain = require('./blockchain');
 const Block = require('./block');
+const cryptoHash = require('./crypto-hash');
 
 describe('Blockchain', () => {
   let blockchain, newChain, originalChain;
@@ -58,6 +59,25 @@ describe('Blockchain', () => {
         });
       });
 
+      describe('and the chain contains a block with a jumped difficulty', () => {
+        it('returns false', () => {
+          const lastBlock = blockchain.chain[blockchain.chain.length-1];
+          const lastHash = lastBlock.hash;
+          const timestamp = Date.now();
+          const nonce = 0;
+          const data = [];
+          const difficulty = lastBlock.difficulty - 3;
+          const hash = cryptoHash(timestamp, lastHash, difficulty, nonce, data);
+          const badBlock = new Block({
+            timestamp, lastHash, hash, nonce, difficulty, data
+          });
+
+          blockchain.chain.push(badBlock);
+
+          expect(Blockchain.isValidChain(blockchain.chain)).toBe(false);
+        });
+      });
+
       describe('and the chain does not contain any invalid blocks', () => {
         it('returns true', () => {
           expect(Blockchain.isValidChain(blockchain.chain)).toBe(true);

index.js

@@ -0,0 +1,54 @@
+const bodyParser = require('body-parser');
+const express = require('express');
+const request = require('request');
+const Blockchain = require('./blockchain');
+const PubSub = require('./pubsub');
+
+const app = express();
+const blockchain = new Blockchain();
+const pubsub = new PubSub({ blockchain });
+
+const DEFAULT_PORT = 3000;
+const ROOT_NODE_ADDRESS = `http://localhost:${DEFAULT_PORT}`;
+
+app.use(bodyParser.json());
+
+app.get('/api/blocks', (req, res) => {
+  res.json(blockchain.chain);  
+});
+
+app.post('/api/mine', (req, res) => {
+  const { data } = req.body;
+
+  blockchain.addBlock({ data });
+
+  pubsub.broadcastChain();
+
+  res.redirect('/api/blocks');
+});
+
+const syncChains = () => {
+  request({ url: `${ROOT_NODE_ADDRESS}/api/blocks` }, (error, response, body) => {
+    if (!error && response.statusCode === 200) {
+      const rootChain = JSON.parse(body);
+
+      console.log('replace chain on a sync with', rootChain);
+      blockchain.replaceChain(rootChain);
+    }
+  });
+};
+
+let PEER_PORT;
+
+if (process.env.GENERATE_PEER_PORT === 'true') {
+  PEER_PORT = DEFAULT_PORT + Math.ceil(Math.random() * 1000);
+}
+
+const PORT = PEER_PORT || DEFAULT_PORT;
+app.listen(PORT, () => {
+  console.log(`listening at localhost:${PORT}`);
+
+  if (PORT !== DEFAULT_PORT) {
+    syncChains();
+  }
+});