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sudo-vaibhav/app.js

Created July 12, 2020 09:27
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  1. sudo-vaibhav created this gist Jul 12, 2020.
    165 changes: 165 additions & 0 deletions app.js
    View file
    Original file line number Diff line number Diff line change
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    //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)
    })