├── README.md
└── nodejs
    └── part1
        ├── README.md
        ├── package-lock.json
        ├── package.json
        ├── src
            ├── api.js
            ├── block.js
            ├── blockchain.js
            ├── consensus.js
            ├── server.js
            └── utils.js
        └── test
            ├── block.js
            ├── blockchain.js
            └── consensus.js


/README.md:
--------------------------------------------------------------------------------
 1 | # kauri-learn-to-build-a-blockchain
 2 | 
 3 | Source code for Kauri series of articles on [Creating a Blockchain](https://kauri.io/article/92034a0c23ed4cb4a6ca959e0a4b78b9/)
 4 | 
 5 | ## Contents
 6 | 
 7 | 1. Part 1: [Blocks & Consensus](/nodejs/part1)
 8 | 1. Part 2: Transactions, wallets and public/private keys - coming soon
 9 | 1. Part 3: Transactions with state (alternative to UTXO)
10 | 
11 | ## Contributing
12 | 
13 | Contributions are welcome! Please feel free to submit a PR and/or a [Kauri](https://kauri.io) article
14 | 


--------------------------------------------------------------------------------
/nodejs/part1/README.md:
--------------------------------------------------------------------------------
 1 | # kauri-learn-to-build-a-blockchain Part1: Blocks & Consensus
 2 | 
 3 | Source code for Kauri series of articles on [Creating a Blockchain | Blocks & Consensus](https://kauri.io/article/92034a0c23ed4cb4a6ca959e0a4b78b9/)
 4 | 
 5 | ## Installation
 6 | 
 7 | 1. Install [Node & NPM](https://nodejs.org)
 8 | 2. Clone this respo
 9 | 3. Run `npm install`
10 | 
11 | ## Run
12 | 
13 | Start a node
14 | 
15 | ```
16 | node src/server.js port=<port>
17 | ```
18 | 
19 | Mine a block
20 | 
21 | ```
22 | curl -X POST "localhost:<port>/mine" -H 'Content-Type: application/json' -d'
23 | {
24 |     "data": "Mine a block on node 1"
25 | }
26 | '
27 | ```
28 | 
29 | Add peer to node
30 | 
31 | ```
32 | curl -X POST "localhost:<port>/peers/add"  -H 'Content-Type: application/json' -d'
33 | {
34 |     "peers":  ["http://<host>:<port>"]
35 | }
36 | '
37 | ```
38 | 
39 | ## Contributing
40 | 
41 | Contributions are welcome! Please feel free to submit a PR and/or a [Kauri](https://kauri.io) article
42 | 


--------------------------------------------------------------------------------
/nodejs/part1/package-lock.json:
--------------------------------------------------------------------------------
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1198 |       "requires": {
1199 |         "isexe": "^2.0.0"
1200 |       }
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1232 |           "integrity": "sha1-754xOG8DGn8NZDr4L95QxFfvAMs=",
1233 |           "requires": {
1234 |             "number-is-nan": "^1.0.0"
1235 |           }
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1242 |             "code-point-at": "^1.0.0",
1243 |             "is-fullwidth-code-point": "^1.0.0",
1244 |             "strip-ansi": "^3.0.0"
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1260 |       "integrity": "sha1-tSQ9jz7BqjXxNkYFvA0QNuMKtp8="
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1265 |       "integrity": "sha1-pcbVMr5lbiPbgg77lDofBJmNY68="
1266 |     },
1267 |     "y18n": {
1268 |       "version": "4.0.0",
1269 |       "resolved": "https://registry.npmjs.org/y18n/-/y18n-4.0.0.tgz",
1270 |       "integrity": "sha512-r9S/ZyXu/Xu9q1tYlpsLIsa3EeLXXk0VwlxqTcFRfg9EhMW+17kbt9G0NrgCmhGb5vT2hyhJZLfDGx+7+5Uj/w=="
1271 |     },
1272 |     "yargs": {
1273 |       "version": "13.2.2",
1274 |       "resolved": "https://registry.npmjs.org/yargs/-/yargs-13.2.2.tgz",
1275 |       "integrity": "sha512-WyEoxgyTD3w5XRpAQNYUB9ycVH/PQrToaTXdYXRdOXvEy1l19br+VJsc0vcO8PTGg5ro/l/GY7F/JMEBmI0BxA==",
1276 |       "requires": {
1277 |         "cliui": "^4.0.0",
1278 |         "find-up": "^3.0.0",
1279 |         "get-caller-file": "^2.0.1",
1280 |         "os-locale": "^3.1.0",
1281 |         "require-directory": "^2.1.1",
1282 |         "require-main-filename": "^2.0.0",
1283 |         "set-blocking": "^2.0.0",
1284 |         "string-width": "^3.0.0",
1285 |         "which-module": "^2.0.0",
1286 |         "y18n": "^4.0.0",
1287 |         "yargs-parser": "^13.0.0"
1288 |       },
1289 |       "dependencies": {
1290 |         "ansi-regex": {
1291 |           "version": "4.1.0",
1292 |           "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-4.1.0.tgz",
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1294 |         },
1295 |         "string-width": {
1296 |           "version": "3.1.0",
1297 |           "resolved": "https://registry.npmjs.org/string-width/-/string-width-3.1.0.tgz",
1298 |           "integrity": "sha512-vafcv6KjVZKSgz06oM/H6GDBrAtz8vdhQakGjFIvNrHA6y3HCF1CInLy+QLq8dTJPQ1b+KDUqDFctkdRW44e1w==",
1299 |           "requires": {
1300 |             "emoji-regex": "^7.0.1",
1301 |             "is-fullwidth-code-point": "^2.0.0",
1302 |             "strip-ansi": "^5.1.0"
1303 |           }
1304 |         },
1305 |         "strip-ansi": {
1306 |           "version": "5.2.0",
1307 |           "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-5.2.0.tgz",
1308 |           "integrity": "sha512-DuRs1gKbBqsMKIZlrffwlug8MHkcnpjs5VPmL1PAh+mA30U0DTotfDZ0d2UUsXpPmPmMMJ6W773MaA3J+lbiWA==",
1309 |           "requires": {
1310 |             "ansi-regex": "^4.1.0"
1311 |           }
1312 |         }
1313 |       }
1314 |     },
1315 |     "yargs-parser": {
1316 |       "version": "13.0.0",
1317 |       "resolved": "https://registry.npmjs.org/yargs-parser/-/yargs-parser-13.0.0.tgz",
1318 |       "integrity": "sha512-w2LXjoL8oRdRQN+hOyppuXs+V/fVAYtpcrRxZuF7Kt/Oc+Jr2uAcVntaUTNT6w5ihoWfFDpNY8CPx1QskxZ/pw==",
1319 |       "requires": {
1320 |         "camelcase": "^5.0.0",
1321 |         "decamelize": "^1.2.0"
1322 |       }
1323 |     },
1324 |     "yargs-unparser": {
1325 |       "version": "1.5.0",
1326 |       "resolved": "https://registry.npmjs.org/yargs-unparser/-/yargs-unparser-1.5.0.tgz",
1327 |       "integrity": "sha512-HK25qidFTCVuj/D1VfNiEndpLIeJN78aqgR23nL3y4N0U/91cOAzqfHlF8n2BvoNDcZmJKin3ddNSvOxSr8flw==",
1328 |       "requires": {
1329 |         "flat": "^4.1.0",
1330 |         "lodash": "^4.17.11",
1331 |         "yargs": "^12.0.5"
1332 |       },
1333 |       "dependencies": {
1334 |         "get-caller-file": {
1335 |           "version": "1.0.3",
1336 |           "resolved": "https://registry.npmjs.org/get-caller-file/-/get-caller-file-1.0.3.tgz",
1337 |           "integrity": "sha512-3t6rVToeoZfYSGd8YoLFR2DJkiQrIiUrGcjvFX2mDw3bn6k2OtwHN0TNCLbBO+w8qTvimhDkv+LSscbJY1vE6w=="
1338 |         },
1339 |         "require-main-filename": {
1340 |           "version": "1.0.1",
1341 |           "resolved": "https://registry.npmjs.org/require-main-filename/-/require-main-filename-1.0.1.tgz",
1342 |           "integrity": "sha1-l/cXtp1IeE9fUmpsWqj/3aBVpNE="
1343 |         },
1344 |         "yargs": {
1345 |           "version": "12.0.5",
1346 |           "resolved": "https://registry.npmjs.org/yargs/-/yargs-12.0.5.tgz",
1347 |           "integrity": "sha512-Lhz8TLaYnxq/2ObqHDql8dX8CJi97oHxrjUcYtzKbbykPtVW9WB+poxI+NM2UIzsMgNCZTIf0AQwsjK5yMAqZw==",
1348 |           "requires": {
1349 |             "cliui": "^4.0.0",
1350 |             "decamelize": "^1.2.0",
1351 |             "find-up": "^3.0.0",
1352 |             "get-caller-file": "^1.0.1",
1353 |             "os-locale": "^3.0.0",
1354 |             "require-directory": "^2.1.1",
1355 |             "require-main-filename": "^1.0.1",
1356 |             "set-blocking": "^2.0.0",
1357 |             "string-width": "^2.0.0",
1358 |             "which-module": "^2.0.0",
1359 |             "y18n": "^3.2.1 || ^4.0.0",
1360 |             "yargs-parser": "^11.1.1"
1361 |           }
1362 |         },
1363 |         "yargs-parser": {
1364 |           "version": "11.1.1",
1365 |           "resolved": "https://registry.npmjs.org/yargs-parser/-/yargs-parser-11.1.1.tgz",
1366 |           "integrity": "sha512-C6kB/WJDiaxONLJQnF8ccx9SEeoTTLek8RVbaOIsrAUS8VrBEXfmeSnCZxygc+XC2sNMBIwOOnfcxiynjHsVSQ==",
1367 |           "requires": {
1368 |             "camelcase": "^5.0.0",
1369 |             "decamelize": "^1.2.0"
1370 |           }
1371 |         }
1372 |       }
1373 |     }
1374 |   }
1375 | }
1376 | 


--------------------------------------------------------------------------------
/nodejs/part1/package.json:
--------------------------------------------------------------------------------
 1 | {
 2 |   "name": "blockchain-js",
 3 |   "version": "1.0.0",
 4 |   "description": "Learn to implement a blockchain in javascript ",
 5 |   "main": "index.js",
 6 |   "scripts": {
 7 |     "test": "mocha test"
 8 |   },
 9 |   "keywords": [
10 |     "blockchain",
11 |     "tutorial",
12 |     "javascript"
13 |   ],
14 |   "author": "@joshorig",
15 |   "license": "MIT",
16 |   "dependencies": {
17 |     "body-parser": "^1.18.3",
18 |     "crypto-js": "^3.1.9-1",
19 |     "express": "^4.16.4",
20 |     "mocha": "^6.1.4",
21 |     "multer": "^1.4.1",
22 |     "node-fetch": "^2.3.0",
23 |     "url-parse": "^1.4.4",
24 |     "uuid": "^3.3.2"
25 |   }
26 | }
27 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/api.js:
--------------------------------------------------------------------------------
  1 | "use strict";
  2 | 
  3 | 
  4 | 
  5 | (async () => {
  6 | 
  7 |   const express     = require('express');
  8 |   const bodyParser  = require('body-parser');
  9 |   const multer      = require('multer');
 10 |   const Utils       = require('./utils');
 11 | 
 12 |   function getAPI(blockchain) {
 13 |     var app = express();
 14 |     const requestParser = multer();
 15 |     app.use(bodyParser.json());
 16 |     //app.use(bodyParser.urlencoded({ extended: true })); // for parsing application/x-www-form-urlencoded
 17 | 
 18 |     app.post('/mine', requestParser.array(), async (req, res) => {
 19 |       const { data }  = req.body || {};
 20 | 
 21 |       if (!data) {
 22 |         res.status(400).send('Error: Must set data in request');
 23 |         return;
 24 |       }
 25 | 
 26 |       await blockchain.checkLongestChain();
 27 | 
 28 |       let block = blockchain.newBlock(data);
 29 | 
 30 |       const response = {
 31 |         message: 'Mined new block',
 32 |         ...block
 33 |       };
 34 | 
 35 |       res.status(201).send(response);
 36 |     });
 37 | 
 38 |     app.get('/blocks', (req, res) => {
 39 |       const response = {
 40 |         blocks: blockchain.blocks,
 41 |         count: blockchain.blocks.length
 42 |       };
 43 | 
 44 |       res.send(response);
 45 |     });
 46 | 
 47 |     app.get('/peers', (req, res) => {
 48 |       const response = {
 49 |         peers: blockchain.peers,
 50 |         count: blockchain.peers.length
 51 |       };
 52 | 
 53 |       res.send(response);
 54 |     });
 55 | 
 56 |     app.post('/peers/add', requestParser.array(), (req, res) => {
 57 |       const { peers } = req.body || [];
 58 | 
 59 |       if (!peers) {
 60 |         res.status(400).send('Error: Must supply list of peers in field peers');
 61 |         return;
 62 |       }
 63 | 
 64 |       peers.forEach((peer) => {
 65 |         blockchain.registerPeer(peer);
 66 |       });
 67 | 
 68 |       const response = {
 69 |         message: 'New peers have been added',
 70 |         peers: JSON.stringify([...blockchain.peers]),
 71 |         count: blockchain.peers.size
 72 |       };
 73 | 
 74 |       res.status(201).send(response);
 75 |     });
 76 | 
 77 |     app.get('/peers/check', async (req, res) => {
 78 |       let response;
 79 |       let result = await blockchain.checkLongestChain();
 80 |       if(result) {
 81 |         response = {
 82 |           message: 'Chain is longest',
 83 |           newChain: blockchain.blocks
 84 |         };
 85 |       }
 86 |       else {
 87 |         response = {
 88 |           message: 'Chain updated',
 89 |           newChain: blockchain.blocks
 90 |         };
 91 |       }
 92 |       res.send(response);
 93 | 
 94 |     });
 95 | 
 96 |     return app;
 97 |   }
 98 | 
 99 |   module.exports = {
100 |     getAPI
101 |   }
102 | })();
103 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/block.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 | 
 5 |   const Utils = require("./utils");
 6 | 
 7 |   function Block(blockNumber,data,nonce,previousBlockHash){
 8 |     this.blockNumber = blockNumber;
 9 |     this.data = data;
10 |     this.nonce = nonce;
11 |     this.previousBlockHash = previousBlockHash
12 |     this.timestamp = Date.now()
13 |     this.hash = "";
14 |   }
15 | 
16 |   Block.prototype.incrementNonce = function() {
17 |     this.nonce++;
18 |     this.hash = Utils.calculateHash(this);
19 |   }
20 | 
21 |   Block.prototype.toString = function() {
22 |       let blockDetails = {
23 |         previousBlockHash: this.previousBlockHash,
24 |         data: this.data,
25 |         blockNumber: this.blockNumber,
26 |         timestamp: this.timestamp,
27 |         nonce: this.nonce,
28 |         blockHash: this.hash
29 |       }
30 |       return JSON.stringify(blockDetails, Object.keys(blockDetails).sort());
31 |    };
32 | 
33 |   module.exports = Block;
34 | })();
35 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/blockchain.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 | 
 5 |   const Consensus   = require('./consensus')
 6 |   const parse       = require('url-parse');
 7 |   const Utils = require("./utils");
 8 | 
 9 | 
10 |   function Blockchain(consensus,blocks){
11 |     this.blocks = [] //the chain of blocks!
12 |     if(blocks)
13 |     {
14 |       this.blocks = blocks;
15 |     }
16 |     this.peers = new Set(); //list of unique peers in the network
17 |     this.consensus = consensus;
18 |     //Create the genesis block
19 |     this.newBlock("I am genesis!")
20 |   }
21 | 
22 |   Blockchain.prototype.newBlock = function(data) {
23 |     let previousBlockHash = "";
24 |     let newBlockNumber = 0
25 |     if(this.blocks.length>0) {
26 |       previousBlockHash = this.blocks[this.blocks.length-1].hash;
27 |       newBlockNumber = this.blocks.length;
28 |     }
29 |     let block = this.consensus.mineBlock(newBlockNumber,data,previousBlockHash);
30 |     this.blocks.push(block);
31 |     return block;
32 |   }
33 | 
34 |   Blockchain.prototype.isValid = function() {
35 |     let currentblockNumber = 1; //start after the genesis block (blockNumber=0)
36 |     while(currentblockNumber < this.blocks.length) {
37 |       const currentBlock = this.blocks[currentblockNumber];
38 |       const previousBlock = this.blocks[currentblockNumber - 1];
39 | 
40 |       // Check that previousBlockHash is correct
41 |       if (currentBlock.previousBlockHash !== previousBlock.hash) {
42 |         return false;
43 |       }
44 | 
45 |       // check that the current blockHash is correct
46 |       if(currentBlock.hash !== Utils.calculateHash(currentBlock)) {
47 |         return false;
48 |       }
49 | 
50 |       // Check that the nonce (proof of work result) is correct
51 |       if (!this.consensus.validHash(currentBlock.hash)) {
52 |         return false;
53 |       }
54 |       currentblockNumber++;
55 |     }
56 | 
57 |     return true;
58 |   }
59 | 
60 |   Blockchain.prototype.registerPeer = function(address) {
61 |     const host = parse(address).host;
62 |     this.peers.add(host);
63 |     console.log("Registered peer: "+host)
64 |   }
65 | 
66 |   Blockchain.prototype.checkLongestChain = async function() {
67 |     let result = await this.consensus.checkLongestChain(this.peers,this.blocks.length);
68 |     if(result.newBlocks) {
69 |       this.blocks = result.newBlocks;
70 |       console.log("Chain replaced: "+this.blocks)
71 |     }
72 |     return result.isLongestChain;
73 |   }
74 | 
75 |   module.exports = Blockchain;
76 | })();
77 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/consensus.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 | 
 5 |   const Block   = require('./block');
 6 |   const Utils   = require('./utils');
 7 |   const fetch   = require('node-fetch');
 8 | 
 9 |   function Consensus(){
10 |     this.difficulty = 5;
11 |     this.difficultyRegex = new RegExp('^0{'+this.difficulty+'}')
12 |   }
13 | 
14 |   Consensus.prototype.mineBlock = function(blockNumber,data,previousBlockHash) {
15 |     let block = new Block(blockNumber,data,0,previousBlockHash); //start the nonce at 0
16 |     //while we have not got the correct number of leadings 0's (difficulty * 0) in our blockHash, keep incrimenting the blocks nonce
17 |     while(!this.validHash(block.hash))
18 |     {
19 |       block.incrementNonce();
20 |     }
21 |     console.log("Mined new block: "+block.toString());
22 |     return block;
23 |   }
24 | 
25 |   Consensus.prototype.validHash = function(hash) {
26 |     return this.difficultyRegex.test(hash);
27 |   }
28 | 
29 |   Consensus.prototype.checkLongestChain = function(peers,length)
30 |   {
31 |     let promises = [];
32 | 
33 |     peers.forEach((host) => {
34 |       promises.push(
35 |         fetch('http://'+host+'/blocks')
36 |           .then(res => {
37 |             if (res.ok) {
38 |               return res.json();
39 |             }
40 |           })
41 |           .then(json => json)
42 |       );
43 |     });
44 | 
45 |     return Promise.all(promises).then((chains) => {
46 |       let newBlocks = null;
47 |       let longestLength = length;
48 | 
49 |       chains.forEach(({ blocks }) => {
50 |         // Check if the length is longer and the chain is valid
51 |         if (blocks.length > longestLength && this.isChainValid(blocks)) {
52 |           longestLength = blocks.length;
53 |           newBlocks = blocks;
54 |         }
55 |       });
56 | 
57 |       return { isLongestChain: !newBlocks, newBlocks: newBlocks };
58 |     });
59 |   }
60 | 
61 |   Consensus.prototype.isChainValid = function(blocks) {
62 |     let currentblockNumber = 1; //start after the genesis block (blockNumber=0)
63 |     while(currentblockNumber < blocks.length) {
64 |       const currentBlock = blocks[currentblockNumber];
65 |       const previousBlock = blocks[currentblockNumber - 1];
66 | 
67 |       // Check that previousBlockHash is correct
68 |       if (currentBlock.previousBlockHash !== previousBlock.hash) {
69 |         return false;
70 |       }
71 |       // check that the current blockHash is correct
72 |       if(currentBlock.hash !== Utils.calculateHash(currentBlock)) {
73 |         return false;
74 |       }
75 |       // Check that the nonce (proof of work result) is correct
76 |       if (!this.validHash(currentBlock.hash)) {
77 |         return false;
78 |       }
79 |       currentblockNumber++;
80 |     }
81 |     return true;
82 |   }
83 | 
84 |   module.exports = Consensus;
85 | })();
86 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/server.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 | 
 5 |   const Utils       = require("./utils");
 6 |   const Api         = require("./api");
 7 |   const Blockchain  = require('../src/blockchain');
 8 |   const Consensus   = require('../src/consensus');
 9 | 
10 |   const DEFAULT_PORT = 5000;
11 |   const args = Utils.parseArgs();
12 | 
13 |   const port = args.port || DEFAULT_PORT;
14 | 
15 |   let app = Api.getAPI(new Blockchain(new Consensus()));
16 |   app.listen(port)
17 |   console.log("Blockchain server listening on port: "+port)
18 | 
19 | 
20 | })();
21 | 


--------------------------------------------------------------------------------
/nodejs/part1/src/utils.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 | 
 5 |   const SHA256  = require("crypto-js/sha256");
 6 |   const UUIDV4    = require("uuid/v4");
 7 | 
 8 |   function getSHA256HexString(input) {
 9 |     return SHA256(input).toString();
10 |   }
11 | 
12 |   function parseArgs() {
13 |     return process.argv
14 |         .slice(2)
15 |         .map(arg => arg.split('='))
16 |         .reduce((args, [value, key]) => {
17 |             args[value] = key;
18 |             return args;
19 |         }, {});
20 |   }
21 | 
22 |   function calculateHash(block) {
23 |     let blockDetails = {
24 |       previousBlockHash: block.previousBlockHash,
25 |       data: block.data,
26 |       blockNumber: block.blockNumber,
27 |       timestamp: block.timestamp,
28 |       nonce: block.nonce
29 |     }
30 |     return getSHA256HexString(JSON.stringify(blockDetails, Object.keys(blockDetails).sort()));
31 |   }
32 | 
33 | 
34 |   module.exports = {
35 |     getSHA256HexString,
36 |     parseArgs,
37 |     calculateHash
38 |   };
39 | 
40 | })();
41 | 


--------------------------------------------------------------------------------
/nodejs/part1/test/block.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 |   // ########################################################################################################
 5 |   // ########################################################################################################
 6 |   // IMPORTS
 7 |   const assert  = require('assert');
 8 |   const Block   = require('../src/block')
 9 | 
10 |   // ########################################################################################################
11 |   // ########################################################################################################
12 |   // TESTS
13 |   describe('Block object tests',  function() {
14 |     // it('Should calculate hash on creation',  function() {
15 |     //   let block = new Block(0,"data",0,"string");
16 |     //   assert.strictEqual(block.hash.length, 64);
17 |     // });
18 | 
19 |   });
20 | })();
21 | 


--------------------------------------------------------------------------------
/nodejs/part1/test/blockchain.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 |   // ########################################################################################################
 5 |   // ########################################################################################################
 6 |   // IMPORTS
 7 |   const assert      = require('assert');
 8 |   const Blockchain  = require('../src/blockchain');
 9 |   const Consensus   = require('../src/consensus');
10 |   const Block       = require('../src/block');
11 | 
12 |   // ########################################################################################################
13 |   // ########################################################################################################
14 |   //
15 |   var blockchain;
16 |   var consensus;
17 |   const BLOCK_TIMEOUT = 60000;
18 | 
19 |   // ########################################################################################################
20 |   // ########################################################################################################
21 |   // TESTS
22 |   describe('Blockchain tests',  function() {
23 |     this.timeout(BLOCK_TIMEOUT*4);
24 | 
25 |     beforeEach(async function() {
26 |       consensus = new Consensus();
27 |       blockchain = new Blockchain(consensus);
28 |     });
29 | 
30 |     it('Should create a genesis block when created',  function() {
31 | 
32 |       assert.strictEqual(blockchain.blocks.length, 1);
33 |       assert.strictEqual(blockchain.blocks[0].data, "I am genesis!");
34 |       assert.strictEqual(blockchain.blocks[0].blockNumber, 0);
35 |     });
36 | 
37 |     it('Should add new valid block',  function() {
38 |       blockchain.newBlock("some data");
39 |       assert.strictEqual(blockchain.blocks.length, 2);
40 |       assert.strictEqual(blockchain.blocks[1].data, "some data");
41 |       assert.strictEqual(blockchain.blocks[1].blockNumber, 1);
42 |       assert.strictEqual(blockchain.isValid(), true);
43 |       blockchain.newBlock("some more data");
44 |       assert.strictEqual(blockchain.blocks.length, 3);
45 |       assert.strictEqual(blockchain.blocks[2].data, "some more data");
46 |       assert.strictEqual(blockchain.blocks[2].blockNumber, 2);
47 |       assert.strictEqual(blockchain.isValid(), true);
48 |     });
49 | 
50 |     it('Should fail to validate blockchain if new block addded with incorrect previous hash',  function() {
51 |       blockchain.newBlock("some data");
52 |       assert.strictEqual(blockchain.isValid(), true);
53 |       let block = consensus.mineBlock(3,"some more data","INVALID_HASH");
54 |       blockchain.blocks.push(block);
55 |       assert.strictEqual(blockchain.isValid(), false);
56 |     });
57 | 
58 |     it('Should fail to validate blockchain if data in a previous block is changed',  function() {
59 |       blockchain.newBlock("some data");
60 |       assert.strictEqual(blockchain.isValid(), true);
61 |       blockchain.newBlock("some more data");
62 |       assert.strictEqual(blockchain.isValid(), true);
63 |       blockchain.blocks[1].data = "invalid data";
64 |       assert.strictEqual(blockchain.isValid(), false);
65 |     });
66 | 
67 |     it('Should fail to validate blockchain if a previous block is swaped for another',  function() {
68 |       blockchain.newBlock("some data");
69 |       assert.strictEqual(blockchain.isValid(), true);
70 |       blockchain.newBlock("some more data");
71 |       assert.strictEqual(blockchain.isValid(), true);
72 |       let block = consensus.mineBlock(2,"some data",blockchain.blocks[0].hash); //regenerating the block should result in a different block hash
73 |       blockchain.blocks[1] = block;
74 |       assert.strictEqual(blockchain.isValid(), false);
75 |     });
76 | 
77 |   });
78 | })();
79 | 


--------------------------------------------------------------------------------
/nodejs/part1/test/consensus.js:
--------------------------------------------------------------------------------
 1 | "use strict";
 2 | 
 3 | (async () => {
 4 |   // ########################################################################################################
 5 |   // ########################################################################################################
 6 |   // IMPORTS
 7 |   const assert  = require('assert');
 8 |   const Consensus   = require('../src/consensus')
 9 | 
10 |   // ########################################################################################################
11 |   // ########################################################################################################
12 |   //
13 |   var consensus;
14 |   const BLOCK_TIMEOUT = 60000;
15 | 
16 |   // ########################################################################################################
17 |   // ########################################################################################################
18 |   // TESTS
19 |   describe('Consensus tests',  function() {
20 | 
21 |     beforeEach(async function() {
22 |       consensus = new Consensus();
23 |     });
24 | 
25 |     it('Should correctly valdidate valid hash',  function() {
26 |       let hashString = "000005622474hwbkvrwhj"
27 |       assert.strictEqual(consensus.validHash(hashString), true);
28 |     });
29 | 
30 |     it('Should fail to valdidate invalid hash',  function() {
31 |       let hashString = "0005622474hwbkvrwhj"
32 |       assert.strictEqual(consensus.validHash(hashString), false);
33 |     });
34 | 
35 |     it('Should create a block with a valid hash',  function() {
36 |       this.timeout(BLOCK_TIMEOUT);
37 |       let block = consensus.mineBlock(0,"some data","PREVIOUS_HASH");
38 |       assert.strictEqual(consensus.validHash(block.hash), true);
39 |     });
40 | 
41 |   });
42 | })();
43 | 


--------------------------------------------------------------------------------