blockchain.js

const Block = require('./block')
const cryptoHash = require('./crypto-hash')

class Blockchain {
    constructor() {
        this.chain = [Block.genesis()]
    }

    addBlock({ data }){
        const newBlock = Block.mineBlock({
            lastBlock: this.chain[this.chain.length - 1],
            data
        });

        this.chain.push(newBlock);
    }

    replaceChain(chain){
        if(chain.length <= this.chain.length) {
            console.error('the incoming chain must be longer');
            return;
        }

        if(!Blockchain.isValidChain(chain)) {
            console.error('the incoming must be invalid');
            return;
        }

        console.log('replaching chain with', chain)
        this.chain = chain;
    }

    static isValidChain(chain){
        if(JSON.stringify(chain[0]) !== JSON.stringify(Block.genesis())) {
            return false;
        }

        for (let i = 1; i < chain.length; i++){
            const { timestamp, lastHash, hash, nonce, difficulty, data } = chain[i]
            const actualHash = chain[i-1].hash;
            const lastDifficulty = chain[i-1].difficulty;

            if(lastHash !== actualHash) return false;

            const validatedHash = cryptoHash(timestamp, lastHash, data, nonce, difficulty);

            if(hash !== validatedHash) return false;

            if(Math.abs(lastDifficulty - difficulty) > 1) return false;
        }

        return true;
    }
}

module.exports = Blockchain;