main.js

'use strict';
var CryptoJS = require("crypto-js");
var express = require("express");
var bodyParser = require('body-parser');
var WebSocket = require("ws");

var http_port = process.env.HTTP_PORT || 8080;
var p2p_port = process.env.P2P_PORT || 6001;
var initialPeers = process.env.PEERS ? process.env.PEERS.split(',') : [];

class Block {
    constructor(index, previousHash, timestamp, data, hash, prime) {
        this.index = index;
        this.previousHash = previousHash.toString();
        this.timestamp = timestamp;
        this.data = data;
        this.hash = hash.toString();
        this.prime = prime;
    }
}

class Data {
    constructor(id, prime) {
        this.id = id
        this.prime = prime
    }
}

var sockets = [];
var MessageType = {
    QUERY_LATEST: 0,
    QUERY_ALL: 1,
    RESPONSE_BLOCKCHAIN: 2
};

var getGenesisBlock = () => {
    return new Block(0, "0", new Date().getTime(), new Data("0xC542d367574d46bc70910d2038b4296461be0A51", "6B404E387FBC5BC11368B86A5290F0688C2A730FAE118C13AFE5B73E16902D7D"), "E48C178426D9F369C83A3B4E03F8B789317D4BB7BA30CECDFF67E29F61EA14DE", 10303);
};

var blockchain = [getGenesisBlock()];

var initHttpServer = () => {
    var app = express();
    app.use(bodyParser.json());

    app.get('/blocks', (req, res) => {
        res.setHeader('Content-Type', 'application/json');
        res.send(JSON.stringify(blockchain))
    });
    app.post('/mineBlock', (req, res) => {
        console.log(req.body.data);
        var newBlock = generateNextBlock(req.body.data);
        if (!addBlock(newBlock) ) {
            res.status(400).send({ message: "invalid block" });
        } else {
            broadcast(responseLatestMsg());
            console.log('block added: ' + JSON.stringify(newBlock));
            res.send({message: "valid block added to the blockchain"});
        }
    });
    app.get('/peers', (req, res) => {
        res.send(sockets.map(s => s._socket.remoteAddress + ':' + s._socket.remotePort));
    });
    app.post('/addPeer', (req, res) => {
        connectToPeers([req.body.peer]);
        res.send();
    });
    app.listen(http_port, () => console.log('Listening http on port: ' + http_port));

};


var initP2PServer = () => {
    var server = new WebSocket.Server({port: p2p_port});
    server.on('connection', ws => initConnection(ws));
    console.log('listening websocket p2p port on: ' + p2p_port);

};

var initConnection = (ws) => {
    sockets.push(ws);
    initMessageHandler(ws);
    initErrorHandler(ws);
    write(ws, queryChainLengthMsg());
};

var initMessageHandler = (ws) => {
    ws.on('message', (data) => {
        var message = JSON.parse(data);
        console.log('Received message' + JSON.stringify(message));
        switch (message.type) {
            case MessageType.QUERY_LATEST:
                write(ws, responseLatestMsg());
                break;
            case MessageType.QUERY_ALL:
                write(ws, responseChainMsg());
                break;
            case MessageType.RESPONSE_BLOCKCHAIN:
                handleBlockchainResponse(message);
                break;
        }
    });
};

var initErrorHandler = (ws) => {
    var closeConnection = (ws) => {
        console.log('connection failed to peer: ' + ws.url);
        sockets.splice(sockets.indexOf(ws), 1);
    };
    ws.on('close', () => closeConnection(ws));
    ws.on('error', () => closeConnection(ws));
};


var generateNextBlock = (blockData) => {
    var previousBlock = getLatestBlock();
    var nextIndex = previousBlock.index + 1;
    var nextTimestamp = new Date().getTime() / 1000;
    var nextPrime = calculateNextPrime(previousBlock.prime)
    var nextHash = calculateHash(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextPrime);
    return new Block(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextHash, nextPrime);
};

var calculateNextPrime = (prevPrime) => {
    for (var i = prevPrime+1; i < prevPrime * prevPrime; i++) {
        if (isPrime(i)) {
            return i;
        }
    }
}

var isPrime = (possiblePrime) => {
    if (possiblePrime % 2 == 0) {
        return false;
    }
    for (var i = 2; i < possiblePrime; i++) {
        if (i % 100000000 == 0) {
            console.log("1000 Million tests!!!");
        }
        if (possiblePrime % i == 0) {
            return false;
        }
    }
    return true;
}

var calculateHashForBlock = (block) => {
    return calculateHash(block.index, block.previousHash, block.timestamp, block.data, block.prime);
};

var calculateHashForPrime = (prime) => {
    return calculateHash("","","","",prime).toUpperCase();
} 

var calculateHash = (index, previousHash, timestamp, data, prime) => {
    return CryptoJS.SHA256(index + previousHash + timestamp + data + prime).toString();
};

var addBlock = (newBlock) => {
    if (isValidNewBlock(newBlock, getLatestBlock())) {
        blockchain.push(newBlock);
        return true;
    }
    else {
        return false;
    }
};

var isValidNewBlock = (newBlock, previousBlock) => {
    if (calculateHashForPrime(newBlock.prime)  != newBlock.data.prime) {
        console.log('prime in data is not the next valid prime');
        return false;
    }
    if (previousBlock.index + 1 !== newBlock.index) {
        console.log('invalid index');
        return false;
    } else if (previousBlock.hash !== newBlock.previousHash) {
        console.log('invalid previoushash');
        return false;
    } else if (calculateHashForBlock(newBlock) !== newBlock.hash) {
        console.log(typeof (newBlock.hash) + ' ' + typeof calculateHashForBlock(newBlock));
        console.log('invalid hash: ' + calculateHashForBlock(newBlock) + ' ' + newBlock.hash);
        return false;
    }
    return true;
};

var connectToPeers = (newPeers) => {
    newPeers.forEach((peer) => {
        var ws = new WebSocket(peer);
        ws.on('open', () => initConnection(ws));
        ws.on('error', () => {
            console.log('connection failed')
        });
    });
};

var handleBlockchainResponse = (message) => {
    var receivedBlocks = JSON.parse(message.data).sort((b1, b2) => (b1.index - b2.index));
    var latestBlockReceived = receivedBlocks[receivedBlocks.length - 1];
    var latestBlockHeld = getLatestBlock();
    if (latestBlockReceived.index > latestBlockHeld.index) {
        console.log('blockchain possibly behind. We got: ' + latestBlockHeld.index + ' Peer got: ' + latestBlockReceived.index);
        if (latestBlockHeld.hash === latestBlockReceived.previousHash) {
            console.log("We can append the received block to our chain");
            blockchain.push(latestBlockReceived);
            broadcast(responseLatestMsg());
        } else if (receivedBlocks.length === 1) {
            console.log("We have to query the chain from our peer");
            broadcast(queryAllMsg());
        } else {
            console.log("Received blockchain is longer than current blockchain");
            replaceChain(receivedBlocks);
        }
    } else {
        console.log('received blockchain is not longer than current blockchain. Do nothing');
    }
};

var replaceChain = (newBlocks) => {
    if (isValidChain(newBlocks) && newBlocks.length > blockchain.length) {
        console.log('Received blockchain is valid. Replacing current blockchain with received blockchain');
        blockchain = newBlocks;
        broadcast(responseLatestMsg());
    } else {
        console.log('Received blockchain invalid');
    }
};

var isValidChain = (blockchainToValidate) => {
    if (blockchainToValidate[0].previousHash !== blockchain[0].previousHash || blockchainToValidate[0].hash !== blockchain[0].hash) {
        console.log("Genesis blocks do not match with peers!");
        return false;
    }
    var tempBlocks = [blockchainToValidate[0]];
    for (var i = 1; i < blockchainToValidate.length; i++) {
        if (isValidNewBlock(blockchainToValidate[i], tempBlocks[i - 1])) {
            tempBlocks.push(blockchainToValidate[i]);
        } else {
            console.log(`Block with index:${i} hash:${blockchainToValidate[i].hash} and prime:${blockchainToValidate[i].prime} is invalid!`);
            return false;
        }
    }
    return true;
};

var getLatestBlock = () => blockchain[blockchain.length - 1];
var queryChainLengthMsg = () => ({'type': MessageType.QUERY_LATEST});
var queryAllMsg = () => ({'type': MessageType.QUERY_ALL});
var responseChainMsg = () =>({
    'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify(blockchain)
});
var responseLatestMsg = () => ({
    'type': MessageType.RESPONSE_BLOCKCHAIN,
    'data': JSON.stringify([getLatestBlock()])
});

var write = (ws, message) => ws.send(JSON.stringify(message));
var broadcast = (message) => sockets.forEach(socket => write(socket, message));

connectToPeers(initialPeers);
initHttpServer();
initP2PServer();