Repository: seanseany/blockchain
Branch: master
Commit: e03e2bbea668
Files: 11
Total size: 14.1 KB

Directory structure:
gitextract_mjm9mmw7/

├── .gitignore
├── Block.js
├── Blockchain.js
├── LICENSE.ISC.txt
├── Messages.js
├── P2p.js
├── README.md
├── cli.js
├── index.js
├── message-type.js
└── package.json

================================================
FILE CONTENTS
================================================

================================================
FILE: .gitignore
================================================
node_modules
.DS_Store

================================================
FILE: Block.js
================================================
class Block {
  constructor (index, previousHash, timestamp, data, hash, nonce) {
    this.index = index;
    this.previousHash = previousHash;
    this.timestamp = timestamp;
    this.data = data;
    this.hash = hash;
    this.nonce = nonce;
  }

  static get genesis() {
    return new Block(
      0,
      "0",
      1508270000000,
      "Welcome to Blockchain Demo 2.0!",
      "000dc75a315c77a1f9c98fb6247d03dd18ac52632d7dc6a9920261d8109b37cf",
      604
    );
  }
}

module.exports = Block;

================================================
FILE: Blockchain.js
================================================
const Block = require("./Block.js");
const crypto = require("crypto");

class Blockchain {
  constructor() {
    this.blockchain = [Block.genesis];
    this.difficulty = 3;
  }

  get() {
    return this.blockchain;
  }

  get latestBlock() {
    return this.blockchain[this.blockchain.length - 1];
  }

  isValidHashDifficulty(hash) {
    for (var i = 0; i < hash.length; i++) {
      if (hash[i] !== "0") {
        break;
      }
    }
    return i >= this.difficulty;
  }

  calculateHashForBlock(block) {
    const { index, previousHash, timestamp, data, nonce } = block;
    return this.calculateHash(
      index,
      previousHash,
      timestamp,
      data,
      nonce
    );
  }

  calculateHash(index, previousHash, timestamp, data, nonce) {
    return crypto
      .createHash("sha256")
      .update(index + previousHash + timestamp + data + nonce)
      .digest("hex");
  }

  mine(data) {
    const newBlock = this.generateNextBlock(data);
    try {
      this.addBlock(newBlock);
    } catch(err) {
      throw err;
    }
  }

  generateNextBlock(data) {
    const nextIndex = this.latestBlock.index + 1;
    const previousHash = this.latestBlock.hash;
    let timestamp = new Date().getTime();
    let nonce = 0;
    let nextHash = this.calculateHash(
      nextIndex,
      previousHash,
      timestamp,
      data,
      nonce
    );

    while (!this.isValidHashDifficulty(nextHash)) {
      nonce = nonce + 1;
      timestamp = new Date().getTime();
      nextHash = this.calculateHash(
        nextIndex,
        previousHash,
        timestamp,
        data,
        nonce
      );
    }

    const nextBlock = new Block(
      nextIndex,
      previousHash,
      timestamp,
      data,
      nextHash,
      nonce
    );

    return nextBlock;
  }

  addBlock(newBlock) {
    if (this.isValidNextBlock(newBlock, this.latestBlock)) {
      this.blockchain.push(newBlock);
    } else {
      throw "Error: Invalid block";
    }
  }

  isValidNextBlock(nextBlock, previousBlock) {
    const nextBlockHash = this.calculateHashForBlock(nextBlock);

    if (previousBlock.index + 1 !== nextBlock.index) {
      return false;
    } else if (previousBlock.hash !== nextBlock.previousHash) {
      return false;
    } else if (nextBlockHash !== nextBlock.hash) {
      return false;
    } else if (!this.isValidHashDifficulty(nextBlockHash)) {
      return false;
    } else {
      return true;
    }
  }

  isValidChain(chain) {
    if (JSON.stringify(chain[0]) !== JSON.stringify(Block.genesis)) {
      return false;
    }

    const tempChain = [chain[0]];
    for (let i = 1; i < chain.length; i = i + 1) {
      if (this.isValidNextBlock(chain[i], tempChain[i - 1])) {
        tempChain.push(chain[i]);
      } else {
        return false;
      }
    }
    return true;
  }

  isChainLonger(chain) {
    return chain.length > this.blockchain.length;
  }

  replaceChain(newChain) {
    if (this.isValidChain(newChain) && this.isChainLonger(newChain)) {
      this.blockchain = JSON.parse(JSON.stringify(newChain));
    } else {
      throw "Error: invalid chain";
    }
  }
}

module.exports = Blockchain;


================================================
FILE: LICENSE.ISC.txt
================================================
ISC License

Copyright (c) 2017, Sean Han

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.


================================================
FILE: Messages.js
================================================
const messageType = require("./message-type.js");
const {
  REQUEST_LATEST_BLOCK,
  RECEIVE_LATEST_BLOCK,
  REQUEST_BLOCKCHAIN,
  RECEIVE_BLOCKCHAIN,
  REQUEST_TRANSACTIONS,
  RECEIVE_TRANSACTIONS
} = messageType;

class Messages {
  static getLatestBlock() {
    return {
      type: REQUEST_LATEST_BLOCK
    };
  }

  static sendLatestBlock(block) {
    return {
      type: RECEIVE_LATEST_BLOCK,
      data: block
    };
  }

  static getBlockchain() {
    return {
      type: REQUEST_BLOCKCHAIN
    };
  }

  static sendBlockchain(blockchain) {
    return {
      type: RECEIVE_BLOCKCHAIN,
      data: blockchain
    };
  }
}

module.exports = Messages;

================================================
FILE: P2p.js
================================================
const wrtc = require("wrtc");
const Exchange = require("peer-exchange");
const p2p = new Exchange("Blockchain Demo 2.0", { wrtc: wrtc });
const net = require("net");
const messageType = require("./message-type.js");
const {
  REQUEST_LATEST_BLOCK,
  RECEIVE_LATEST_BLOCK,
  REQUEST_BLOCKCHAIN,
  RECEIVE_BLOCKCHAIN,
  REQUEST_TRANSACTIONS,
  RECEIVE_TRANSACTIONS
} = messageType;
const Messages = require("./Messages.js");

class PeerToPeer {
  constructor(blockchain) {
    this.peers = [];
    this.blockchain = blockchain;
  }

  startServer(port) {
    const server = net
      .createServer(socket =>
        p2p.accept(socket, (err, conn) => {
          if (err) {
            throw err;
          } else {
            this.initConnection.call(this, conn);
          }
        })
      )
      .listen(port);
  }

  discoverPeers() {
    p2p.getNewPeer((err, conn) => {
      if (err) {
        throw err;
      } else {
        this.initConnection.call(this, conn);
      }
    });
  }

  connectToPeer(host, port) {
    const socket = net.connect(port, host, () =>
      p2p.connect(socket, (err, conn) => {
        if (err) {
          throw err;
        } else {
          this.initConnection.call(this, conn);
        }
      })
    );
  }

  closeConnection() {
    p2p.close(err => {
      throw err;
    });
  }

  broadcastLatest() {
    this.broadcast(Messages.sendLatestBlock(this.blockchain.latestBlock));
  }

  broadcast(message) {
    this.peers.forEach(peer => this.write(peer, message));
  }

  write(peer, message) {
    peer.write(JSON.stringify(message));
  }

  initConnection(connection) {
    this.peers.push(connection);
    this.initMessageHandler(connection);
    this.initErrorHandler(connection);
    this.write(connection, Messages.getLatestBlock());
  }

  initMessageHandler(connection) {
    connection.on("data", data => {
      const message = JSON.parse(data.toString("utf8"));
      this.handleMessage(connection, message);
    });
  }

  initErrorHandler(connection) {
    connection.on("error", err => {
      throw err;
    });
  }

  handleMessage(peer, message) {
    switch (message.type) {
      case REQUEST_LATEST_BLOCK:
        this.write(peer, Messages.sendLatestBlock(this.blockchain.latestBlock));
        break;
      case REQUEST_BLOCKCHAIN:
        this.write(peer, Messages.sendBlockchain(this.blockchain.get()));
        break;
      case RECEIVE_LATEST_BLOCK:
        this.handleReceivedLatestBlock(message, peer);
        break;
      case RECEIVE_BLOCKCHAIN:
        this.handleReceivedBlockchain(message);
        break;
      default:
        throw "Received invalid message.";
    }
  }

  handleReceivedLatestBlock(message, peer) {
    const receivedBlock = message.data;
    const latestBlock = this.blockchain.latestBlock;

    if (latestBlock.hash === receivedBlock.previousHash) {
      try {
        this.blockchain.addBlock(receivedBlock);
      } catch(err) {
        throw err;
      }
    } else if (receivedBlock.index > latestBlock.index) {
      this.write(peer, Messages.getBlockchain());
    } else {
      // Do nothing.
    }
  }

  handleReceivedBlockchain(message) {
    const receivedChain = message.data;
    
    try {
      this.blockchain.replaceChain(receivedChain);
    } catch(err) {
      throw err;
    }
  }
}

module.exports = PeerToPeer;


================================================
FILE: README.md
================================================
<h1 align="center">
  <br>
  <a href="https://blockchaindemo.io" rel="noopener noreferrer" target="_blank"><img src="https://raw.githubusercontent.com/seanseany/blockchain/master/logo.png" width="200"></a>
  <br>
    <a href="https://blockchaindemo.io" rel="noopener noreferrer" target="_blank">Blockchaindemo.io</a>
  <br>
</h1>

<h4 align="center">Code for learning the blockchain data structure</h4>

<br>

## 📦 Installation

To install this application, you'll need
[Node.js](https://nodejs.org/en/download/) 7+ (which comes with
[npm](http://npmjs.com)) installed on your computer. From your command line:

#### Source

You'll need [Git](https://git-scm.com) to run the project from source. From your
command line:

```bash
# Clone this repository
$ git clone https://github.com/seanseany/blockchain

# Go into the repository
$ cd blockchain

# Install dependencies
$ npm install

# Run the app
$ npm start
```

## ℹ️ FAQ

#### When or why I would use this?

You should use this if you want to build a bitcoin wallet, payment processor, or
bitcoin merchant portal in javascript. You might also be interested in why
decentralized networks or p2p applications are useful, or what advantages they
have; this project seems like a good way to learn about that.

#### What is the block chain actually for?

The blockchain is for authorizing payments of a cryptocurrency between two peers
without the need for a centralized 3rd party approving of the transaction. There
are other uses of the blockchain which are more in line with the second point,
digital signatures, but they are secondary to the main purpose of peer to peer
transfer of value. Bitcoin is blockchain's killer app.

#### Why the hell should I care about the blockchain?

Blockchain facilitates trade over a network. Imagine a metal as scarce as gold
with a magical property of "can be transported over a communications channel".
This has implications with respect to individual rights, the world economy, and
the way we monetize and transfer value at a level higher than bartering directly
for goods.

Lately people are distancing themselves from the proof-of-work concept and are
using blockchain to describe only the mechanism of signing a transaction as
verification of sending an amount. Change "sending an amount" to almost anything
else - authorizing a change in a ruleset, casting a vote for a politician,
verifying a point of IoT data is authentic. Now add in the concept of a
peer-to-peer network to this and you've eliminated a middleman that once
existed, thereby improving the efficiency and reducing cost. In these cases,
"blockchain" refers to the structuring of a program or database in such a way
that it has no central point of failure while still providing all of the
features expected. For example, augur and gnosis are decentralized prediction
markets. Ethereum has implemented smart contracts which enable decentralized
release of funds based on a gambling outcome.


================================================
FILE: cli.js
================================================

const P2p = require("./P2p.js");
const Blockchain = require("./Blockchain.js");
const blockchain = new Blockchain();
const p2p = new P2p(blockchain);

function cli(vorpal) {
  vorpal
  .use(welcome)
  .use(connectCommand)
  .use(discoverCommand)
  .use(blockchainCommand)
  .use(peersCommand)
  .use(mineCommand)
  .use(openCommand)
  .delimiter('blockchain →')
  .show()
}

module.exports = cli;

// COMMANDS
function welcome(vorpal) {
  vorpal.log("Welcome to Blockchain CLI!");
  vorpal.exec("help");
}

function connectCommand(vorpal) {
  vorpal
  .command('connect <host> <port>', "Connect to a new peer. Eg: connect localhost 2727")
  .alias('c')
  .action(function(args, callback) {
    if(args.host && args.port) {
      try {
        p2p.connectToPeer(args.host, args.port);
      } catch(err) {
        this.log(err);
      }
    }
    callback();
  })
}

function discoverCommand(vorpal) {
  vorpal
  .command('discover', 'Discover new peers from your connected peers.')
  .alias('d')
  .action(function(args, callback) {
    try {
      p2p.discoverPeers();
    } catch(err) {
      this.log(err);
    }
    callback();
  })
}

function blockchainCommand(vorpal) {
  vorpal
    .command('blockchain', 'See the current state of the blockchain.')
    .alias('bc')
    .action(function(args, callback) {
      this.log(blockchain)
      callback();
    })
}

function peersCommand(vorpal) {
  vorpal
    .command('peers', 'Get the list of connected peers.')
    .alias('p')
    .action(function(args, callback) {
      p2p.peers.forEach(peer => {
        this.log(`${peer.pxpPeer.socket._host} \n`)
      }, this)
      callback();
    })
}

function mineCommand(vorpal) {
  vorpal
    .command('mine <data>', 'Mine a new block. Eg: mine hello!')
    .alias('m')
    .action(function(args, callback) {
      if (args.data) {
        blockchain.mine(args.data);
        p2p.broadcastLatest(); 
      }
      callback();
    })
}

function openCommand(vorpal) {
  vorpal
    .command('open <port>', 'Open port to accept incoming connections. Eg: open 2727')
    .alias('o')
    .action(function(args, callback) {
      if (args.port) {
        if(typeof args.port === 'number') {
          p2p.startServer(args.port);
          this.log(`Listening to peers on ${args.port}`);
        } else {
          this.log(`Invalid port!`);
        }
      }
      callback();
    })
}

================================================
FILE: index.js
================================================
#!/usr/bin/env node
const vorpal = require('vorpal')();
vorpal.use(require('./cli.js'));

================================================
FILE: message-type.js
================================================
const messageType = {
  REQUEST_LATEST_BLOCK: 0,
  RECEIVE_LATEST_BLOCK: 1,
  REQUEST_BLOCKCHAIN: 2,
  RECEIVE_BLOCKCHAIN: 3,
};

module.exports = messageType;

================================================
FILE: package.json
================================================
{
  "name": "blockchain-cli",
  "version": "2.0.0",
  "description": "Blockchain command-line interface",
  "main": "index.js",
  "engines": {
    "node": "7.0.0",
    "npm": "3.10.8"
  },
  "scripts": {
    "start": "node ./index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "peer-exchange": "^2.2.0",
    "vorpal": "^1.12.0",
    "wrtc": "0.0.63"
  }
}