Merge pull request #149 from dvf/dvf/js

Minimal JS Implementation

.gitignore

@@ -102,3 +102,5 @@ ENV/
 
 # PyCharm
 .idea/
+
+node_modules/

js/blockchain.js

@@ -0,0 +1,102 @@
+const crypto = require("crypto");
+
+
+class Blockchain {
+    constructor() {
+        this.chain = [];
+        this.pendingTransactions = [];
+        this.newBlock();
+        this.peers = new Set();
+    }
+
+    /**
+     * Adds a node to our peer table
+     */
+    addPeer(host) {
+        this.peers.add(host);
+    }
+
+    /**
+     * Adds a node to our peer table
+     */
+    getPeers() {
+        return Array.from(this.peers);
+    }
+
+    /**
+     * Creates a new block containing any outstanding transactions
+     */
+    newBlock(previousHash, nonce = null) {
+        let block = {
+            index: this.chain.length,
+            timestamp: new Date().toISOString(),
+            transactions: this.pendingTransactions,
+            previousHash,
+            nonce
+        };
+
+        block.hash = Blockchain.hash(block);
+
+        console.log(`Created block ${block.index}`);
+
+        // Add the new block to the blockchain
+        this.chain.push(block);
+
+        // Reset pending transactions
+        this.pendingTransactions = [];
+    }
+
+    /**
+     * Generates a SHA-256 hash of the block
+     */
+    static hash(block) {
+        const blockString = JSON.stringify(block, Object.keys(block).sort());
+        return crypto.createHash("sha256").update(blockString).digest("hex");
+    }
+
+    /**
+     * Returns the last block in the chain
+     */
+    lastBlock() {
+        return this.chain.length && this.chain[this.chain.length - 1];
+    }
+
+    /**
+     * Determines if a hash begins with a "difficulty" number of 0s
+     *
+     * @param hashOfBlock: the hash of the block (hex string)
+     * @param difficulty: an integer defining the difficulty
+     */
+    static powIsAcceptable(hashOfBlock, difficulty) {
+        return hashOfBlock.slice(0, difficulty) === "0".repeat(difficulty);
+    }
+
+    /**
+     * Generates a random 32 byte string
+     */
+    static nonce() {
+        return crypto.createHash("sha256").update(crypto.randomBytes(32)).digest("hex");
+    }
+
+    /**
+     * Proof of Work mining algorithm
+     *
+     * We hash the block with random string until the hash begins with
+     * a "difficulty" number of 0s.
+     */
+    mine(blockToMine = null, difficulty = 4) {
+        const block = blockToMine || this.lastBlock();
+
+        while (true) {
+            block.nonce = Blockchain.nonce();
+            if (Blockchain.powIsAcceptable(Blockchain.hash(block), difficulty)) {
+                console.log("We mined a block!")
+                console.log(` - Block hash: ${Blockchain.hash(block)}`);
+                console.log(` - nonce:      ${block.nonce}`);
+                return block;
+            }
+        }
+    }
+}
+
+module.exports = Blockchain;

js/index.js

@@ -0,0 +1,37 @@
+const Blockchain = require("./blockchain");
+const {send} = require("micro");
+
+const blockchain = new Blockchain();
+
+
+module.exports = async (request, response) => {
+    const route = request.url;
+
+    // Keep track of the peers that have contacted us
+    blockchain.addPeer(request.headers.host);
+
+    let output;
+
+    switch (route) {
+        case "/new_block":
+            output = blockchain.newBlock();
+            break;
+
+        case "/last_block":
+            output = blockchain.lastBlock();
+            break;
+
+        case "/get_peers":
+            output = blockchain.getPeers();
+            break;
+
+        case "/submit_transaction":
+            output = blockchain.addTransaction(transaction);
+            break;
+
+        default:
+            output = blockchain.lastBlock();
+
+    }
+    send(response, 200, output);
+};