server.js

const express = require('express');
const bodyParser = require('body-parser');
const mongoose = require('mongoose');
const Web3 = require('web3');
const contractABI = require('../contractABI.json'); // Replace with your actual contract ABI
const contractAddress = '0xA72D8d4c4611c702dE430124A240E54fC78fA905'; // Replace with your actual contract address
const Voter = require('./voterModel');

// Connect to MongoDB
mongoose.connect('mongodb://localhost:27017/voting', {
  useNewUrlParser: true,
  useUnifiedTopology: true,
});
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'MongoDB connection error:'));

// Mongoose models
const voterSchema = new mongoose.Schema({
  address: { type: String, required: true, unique: true },
  isRegistered: { type: Boolean, default: false },
  hasVoted: { type: Boolean, default: false },
});
const VoterModel = mongoose.model('Voter', voterSchema);

// Express app setup
const app = express();
app.use(bodyParser.json());

// Web3 setup
// Connect to Remix Web3 provider
const web3 = new Web3('https://remix.ethereum.org/#web3-provider');
const contract = new web3.eth.Contract(contractABI, contractAddress);

// API endpoints
app.post('/register', async (req, res) => {
  // Register voter implementation
});

app.post('/vote', async (req, res) => {
  // Vote implementation
});

app.get('/candidates', async (req, res) => {
  // Get candidates implementation
});

// Start listening for events emitted by the smart contract
contract.events.allEvents()
  .on('data', event => {
    console.log('Event:', event.event, event.returnValues);
  })
  .on('error', error => {
    console.error('Event error:', error);
  });

// Server setup
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
  console.log(Server running on port ${PORT});
});

// Documentation endpoint
app.get('/', (req, res) => {
  res.json({
    endpoints: {
      register: {
        description: 'Register a voter',
        method: 'POST',
        path: '/register',
        body: {
          address: 'String (Ethereum address)',
        },
      },
      vote: {
        description: 'Cast a vote',
        method: 'POST',
        path: '/vote',
        body: {
          address: 'String (Ethereum address)',
          candidateName: 'String (Candidate name)',
        },
      },
      candidates: {
        description: 'Get the list of candidates',
        method: 'GET',
        path: '/candidates',
      },
    },
  });
});