Simple Block Chain Mechanism in Dart for Learning Purpose

block.dart

library block;

import 'dart:async';
import 'package:crypto/crypto.dart' show sha256;

class Block {
  int nonce = 0;
  String _hash;
  final int index;
  final int ts;
  final List<int> data;
  String pHash;

  Block({this.index, this.ts, this.data, this.pHash}) {
    _hash = calculateHash();
  }
  get hash => _hash;
  set hash(String hash) => _hash = hash;
  set previousHash(String hash) => pHash = hash;
  get previousHash => pHash;
  Future<bool> mine(int difficulty) async {
    while (_hash.substring(0, difficulty) != "0" * difficulty) {
      nonce++;
      print('\u2717: \x1b[31m$hash\x1b[0m');
      hash = await calculateHash();
    }

    print('\u2713: \x1b[32m$hash\x1b[0m');
    return true;
  }

  String calculateHash() {
    if (pHash == null) pHash = "0";
    data.addAll([index, ts, int.parse(pHash, radix: 35), nonce]);
    return sha256.convert(data).toString();
  }
}

block_chain.dart

import 'dart:async';
import 'block.dart';

class BlockChain {
  final int difficulty = 2; // don't make it harder :D
  List<Block> chain = [];
  BlockChain.createChain() {
    chain = [
      new Block(
          index: 0,
          data: "1".codeUnits.toList(growable: true),
          ts: new DateTime.now().millisecondsSinceEpoch)
    ];
  }
  Future<bool> add(Block block) async {
    block.previousHash = chain.last.hash;
    await block.mine(difficulty);
    chain.add(block);
    if (!_isChainValid()) {
      chain.remove(block);
      return false;
    }
    return true;
  }

  Future<bool> addAll(Iterable<Block> blocks) async {
    for (var block in blocks) {
      await add(block);
    }
    return true;
  }

  bool _isChainValid() {
    for (var i = 1; i < chain.length; i++) {
      var currentBlock = chain[i];
      var previousBlock = chain[i - 1];
      if (currentBlock.previousHash != previousBlock.hash) {
        return false;
      }
    }
    return true;
  }
}

main.dart

library main;
import 'block.dart';
import 'block_chain.dart';

main() async {
  BlockChain chain = new BlockChain.createChain();
  Block block = new Block(
      index: 1,
      ts: new DateTime.now().millisecondsSinceEpoch,
      data: "124".codeUnits.toList(growable: true));
  Block block2 = new Block(
      index: 2,
      ts: new DateTime.now().millisecondsSinceEpoch,
      data: "20".codeUnits.toList(growable: true));
  Block block3 = new Block(
      index: 3,
      ts: new DateTime.now().millisecondsSinceEpoch,
      data: "10".codeUnits.toList(growable: true));
  Block block4 = new Block(
      index: 4,
      ts: new DateTime.now().millisecondsSinceEpoch,
      data: "30".codeUnits.toList(growable: true));
  Block block5 = new Block(
      index: 5,
      ts: new DateTime.now().millisecondsSinceEpoch,
      data: "44".codeUnits.toList(growable: true));
  try {
    await chain.add(block);
    await chain.addAll([block2, block3, block4, block5]);
  } catch (e) {
    print(e);
  }
  print('\x1b[42m\x1b[34m Done added ${chain.chain.length} blocks \x1b[0m');
}

pubspec.yaml

name: blockchain
version: 1.0.0
description: >
  Simple Block Chain Mechanism in Dart for Learning Purpose
author: Shady Khalifa <[email protected]>
dependencies:
  crypto: "^2.0.2+1"