blockchain.js

const sha256 = require('js-sha256')
const Block = require ('./block');


class Blockchain {

  constructor(genesisBlock) {
    this.blocks = [] 
    this.addBlock(genesisBlock)
  }

addBlock(block){

  if(this.blocks.length === 0){
block.previousHash="0000000000000000"
block.hash = this.generateHash(block)
}
  this.blocks.push(block)
}

getNextBlock(transactions){
  const block = new Block()

  transactions.forEach(function(transaction){
    block.addTransaction(transaction)
  })
  const previousBlock = this.getPreviousBlock()
  block.index = this.blocks.length
  block.previousHash = previousBlock.hash
  block.hash  = this.generateHash(block)

  return block
}
getPreviousBlock(){
  return this.blocks[this.blocks.length - 1]
}

generateHash(block){

  let hash = sha256(block.key);

while(!hash.startsWith("000")){

  block.nonce += 1

  hash = sha256(block.key)
  
 // console.log(hash)
}


  return hash

}

}

module.exports = Blockchain