blockchain.js

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

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

    addBlock({data}){
        const newBlock=Block.minedBlock({ lastblock:this.chain[this.chain.length-1], data });
        this.chain.push(newBlock);
    }
    // validation this is where crypto validation is 
    
    static isValidChain(chain){
            //checking if the first chain is genesis 
        if(JSON.stringify(chain[0]) !== JSON.stringify(Block.genesis)){
            return false;
        }
        // validating each of the element in the chain by looing and meeting conditions

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

            if(lastHash !== actualLastHash) 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;
    };
     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 chain must be valid');
             return;
         }
        console.log('replacing the chain with', chain);
         this.chain=chain;

    }
       
}

module.exports=Blockchain;