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blockchain.js
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blockchain.js
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const SHA256 = require("crypto-js/sha256");
const EC = require("elliptic").ec;
const ec = new EC("secp256k1");
class Transaction {
constructor(fromAddress, toAddress, amount) {
this.fromAddress = fromAddress;
this.toAddress = toAddress;
this.amount = amount;
}
calculateHash() {
return SHA256(this.fromAddress + this.toAddress + this.amount).toString();
}
signTransaction(signingkey) {
if (signingkey.getPublic("hex") != this.fromAddress) {
throw new Error("You cannot sign transactions for other wallets");
}
const hashTx = this.calculateHash();
const sig = signingkey.sign(hashTx, "base64");
this.signature = sig.toDER("hex");
}
isValid() {
if (this.fromAddress == null) return true;
if (!this.signature || this.signature.length === 0) {
throw new Error("No Signature in this Transaction");
}
const publicKey = ec.keyFromPublic(this.fromAddress, "hex");
return publicKey.verify(this.calculateHash(), this.signature);
}
}
class Block {
constructor(timestamp, transactions, previousHash = "") {
this.timestamp = timestamp;
this.transactions = transactions;
this.previousHash = previousHash;
this.hash = this.calculateHash();
this.nonce = 0;
}
calculateHash() {
return SHA256(
this.index +
this.timestamp +
this.previousHash +
JSON.stringify(this.data) +
this.nonce
).toString();
}
mineBlock(difficulty) {
while (
this.hash.substring(0, difficulty) != Array(difficulty + 1).join("0")
) {
this.nonce++;
this.hash = this.calculateHash();
}
}
hasValidTransactions() {
for (const tx of this.transactions) {
if (!tx.isValid()) {
return false;
}
}
return true;
}
}
class Blockchain {
constructor() {
this.chain = [this.createGenisisBlock()];
this.difficulty = 2;
this.pendingTranscations = [];
this.miningReward = 100;
}
createGenisisBlock() {
return new Block("04/08/20", "Genesis Block", "0");
}
getLatestblock() {
return this.chain[this.chain.length - 1];
}
minePendingTransactions(miningRewardAddress) {
const rewardTx = new Transaction(
null,
miningRewardAddress,
this.miningReward
);
this.pendingTranscations.push(rewardTx);
let block = new Block(Date.now(), this.pendingTranscations);
block.mineBlock(this.difficulty);
console.log("Block Succesfully Mined");
this.chain.push(block);
this.pendingTranscations = [
new Transaction(null, miningRewardAddress, this.miningReward),
];
}
addTransaction(transaction) {
if (!transaction.fromAddress || !transaction.toAddress)
throw new Error("Transaction must include to and from address");
if (!transaction.isValid()) {
throw new Error("Can't add invalid transaction");
}
this.pendingTranscations.push(transaction);
}
getBalanceOfAddress(address) {
let balance = 0;
for (const block of this.chain) {
for (const trans of block.transactions) {
if (trans.fromAddress == address) {
balance -= trans.amount;
}
if (trans.toAddress == address) {
balance += trans.amount;
}
}
}
return balance;
}
isChainValid() {
for (let index = 1; index < this.chain.length; index++) {
const currentBlock = this.chain[index];
const previousBlock = this.chain[index - 1];
if (!currentBlock.hasValidTransactions()) return false;
if (currentBlock.hash != currentBlock.calculateHash()) {
return false;
}
if (currentBlock.previousHash != previousBlock.hash) {
return false;
}
return true;
}
}
}
module.exports.Blockchain = Blockchain;
module.exports.Transaction = Transaction;