blockchain.ts

import { performance } from "perf_hooks";
import { SHA256 as sha256 } from "crypto-js";

function calculateTarget(difficulty: number): number {
  return Math.ceil(2 ** 256 / difficulty);
}

function padLeft(str: string, to: number, chr: string): string {
  return str.length < to ? padLeft(chr + str, to, chr) : str;
}

class Block {
  public hash: string;
  public nonce: number = 0;

  constructor(
    public index: number,
    public prevHash: string,
    public timestamp: number,
    public data: any,
    public difficulty: number,
  ) {
    this.hash = this.calculateHash();
  }

  calculateHash(): string {
    return sha256(
      this.index +
      this.prevHash +
      this.timestamp +
      JSON.stringify(this.data)
    ).toString();
  }

  mine() {
    const target = calculateTarget(this.difficulty);
    while (
      parseInt(sha256(this.hash + this.nonce).toString(), 16) > target
    ) {
      this.nonce++;
    }
  }
}

class Blockchain {
  public difficulty = 10000;
  public blocks: Block[] = [
    new Block(0, "", Date.now(), "Genesis block!", 0)
  ];

  isBlockValid(block: Block): boolean {
    const prev = this.blocks[block.index - 1];

    if (block.prevHash !== prev.hash) return false;

    const target = calculateTarget(block.difficulty);
    if (parseInt(sha256(block.calculateHash() + block.nonce).toString(), 16) > target) return false;

    return true;
  }

  isBlockchainValid(): boolean {
    for (let i = 1; i < this.blocks.length; i++) {
      if (!this.isBlockValid(this.blocks[i])) return false;
    }
    return true;
  }

  addBlock(block: Block) {
    if (!this.isBlockValid(block)) throw new Error("Invalid block");
    this.blocks.push(block);
  }
}



const blockchain = new Blockchain();

const start = performance.now();

for (let i = 1; i <= 10; i++) {
  const prev = blockchain.blocks[blockchain.blocks.length - 1];
  const block = new Block(i, prev.hash, Date.now(), { amount: i * 100 }, blockchain.difficulty);
  console.log(`Mining block #${i}`);
  block.mine();
  blockchain.addBlock(block);
}

// blockchain.blocks[2].data = { amount: 99999999999999 }

console.log(blockchain.isBlockchainValid());
console.log((performance.now() - start) / 1000);