miner.js

const { sha256 } = require('js-sha256').sha256;

class Miner {
  constructor(fnHash, difficulty = 1, maxAttempts = 1000, verbose = true) {
    if (difficulty <= 0 || difficulty > 5) {
      throw new Error('Invalid difficulty provided');
    }

    this.fnHash = fnHash;
    this.maxAttempts = maxAttempts;
    this.verbose = verbose;
    this.difficulty = difficulty;
    this.nonce = 0;
  }
  getPrefix() {
    return '0'.repeat(this.difficulty);
  }
  mine(merkleRoot) {
    console.log(`Attempting to mine block with Merkle root ${merkleRoot}.`);
    console.log(`Difficulty level: ${this.difficulty}`);

    const startTime = new Date().valueOf();
    const prefix = this.getPrefix();
    for (this.nonce = 0; this.nonce < this.maxAttempts; this.nonce += 1) {
      const hash = this.fnHash(`${merkleRoot}${this.nonce}`);
      this.logAttempt(hash);
      if (String(hash).slice(0, this.difficulty) === prefix) {
        return this.logResult(true, startTime, new Date().valueOf());
      }
    }
    return this.logResult(false, startTime, new Date().valueOf());
  }
  logAttempt(hash) {
    if (this.verbose === true) {
      console.log(`Attempting with nonce ${this.nonce}: ${hash}`);
    }
  }
  logResult(succeeded, startTimeMs, endTimeMs) {
    const elapsed = (endTimeMs - startTimeMs) / 1000;
    if (succeeded) {
      return console.log(`\n*** Block mined after ${this.nonce + 1} attempts in ${elapsed} seconds ***`);
    }
    return console.log(`\n*** Unable to mine block after ${this.nonce} attempts in ${elapsed} seconds ***`);
  }
}