blockchain code

app.js

//setup for the server and other third party node modules
const port = process.env.PORT || 3000
const express = require("express")
const app = express()

// this will allow cross-domain access
const cors = require("cors")
app.use(cors())

//for parsing json content in requests
const bodyParser = require('body-parser')
app.use(bodyParser.json())

//this will help assign a unique id to each block
const {
  v4: uuidv4
} = require('uuid')

//Block class
class Block {
  constructor(proposerId, data) {
    this.proposer = proposerId
    this.data = data
    this.approvals = [proposerId] //obviously a proposer will approve his own block
    this.blockId = uuidv4() //assigns a unique id to each proposal for tracking later
  }

}

//Blockchain class
class Blockchain {
  constructor() {
    this.chain = []
    this.nodes = {}
    this.proposalBuffer = []
  }

  stake(block) {
    this.nodes[block.proposer].balance -= STAKE_AMOUNT
    this.proposalBuffer.push(block)
  }

  runConsensus() {
    console.log("running consensus algorithm now!")
    this.proposalBuffer.forEach(proposal => {
      let approvalsCount = proposal.approvals.length
      let nodesCount = Object.keys(this.nodes).length
      let approvalRatio = (approvalsCount / nodesCount)
      if (approvalRatio > CONSENSUS_THRESHOLD) {
        this.addBlock(proposal)
        //now reward the proposer
        console.log("proposal approved!!", proposal)
        this.nodes[proposal.proposer].balance += REWARD_AMOUNT
      } else {
        //the block doesn't get added and proposer gets less amount of tokens back
        console.log("proposal rejected!!", proposal)
        this.nodes[proposal.proposer].balance += PENALIZED_AMOUNT
      }
    })

    //now we clear the buffer as it has run its course now
    this.proposalBuffer = []
  }

  addBlock(block) {
    this.chain.push(block)
  }

  addNode(node) {
    if (this.nodes[node.id]) {
      return false //means another node with same id already exists
    } else {
      this.nodes[node.id] = node // adding a new node and allocating it the initial balance
      return true
    }
  }


}

//Node class (each medical organisation will be a node on the network)
class Node {
  constructor(id, blockchain) {
    this.id = id
    this.balance = INITIAL_BALANCE
    //now get this node added to blockchain network
    blockchain.addNode(this)
  }

  propose(data) {
    let block = new Block(this.id, data)
    blockchain.stake(block)
    return block.blockId // returns the uuid of proposed block
  }
}

let blockchain = new Blockchain()

app.post("/proposeblock", (req, res) => {
  const {
    id,
    data
  } = req.body
  try {
    const blockId = blockchain.nodes[id].propose(data)
    res.status(200).send({
      blockId
    })
  } catch {
    res.status(404).send("user not found")
  }

})

app.post("/addNode", (req, res) => {
  const {
    id
  } = req.body
  let node = new Node(id, blockchain)
  res.status(200).send("OK")
})


//for adding a 
app.post("/approve", (req, res) => {
  const {
    id,
    blockId
  } = req.body

  for (let proposal of blockchain.proposalBuffer) {
    if (proposal.blockId == blockId) {
      console.log(proposal.approvals)
      if (!proposal.approvals.includes(id)) {
        proposal.approvals.push(id)
      }
      break
    }
  }

  res.status(200).send("OK")
})

app.get("/runconsensus", (req, res) => {
  blockchain.runConsensus()
  res.status(200).send(blockchain)
})

app.get("/blockchain", (req, res) => {
  res.status(200).send(blockchain)
})

app.get("/", (req, res) => {
  res.redirect("/blockchain")
})

app.listen(port, () => {
  console.log(`listening on port ${port}`)

  setInterval(() => {
    // maintains the blockchain periodically by rewarding valuable
    // contributions and penalizing the wrong ones by deducting the staked amount
    blockchain.runConsensus()
  }, THIRTY_MINUTES)
})