app.js

const express = require("express");
const app = express();
const server = require("http").createServer(app);
const path = require("path");
const bodyparser = require("body-parser");
var PaytmChecksum = require("./PaytmChecksum/PaytmChecksum");
const checksum_lib = require('./Paytm/checksum')
const config = require('./Paytm/config');

app.use(express.static('public'));
app.use(express.urlencoded({ extended: true }));

app.set('views', path.join(__dirname, 'views'));
app.set("view engine", "ejs");

app.get('/', (req, res) => {
    res.render('payment');
})
// app.get('/callback', (req, res) => {

// })
app.post("/callback", (req, res) => {
    // Route for verifiying payment

    var body = '';

    req.on('data', function (data) {
        body += data;
    });

    req.on('end', function () {
        var html = "";
        var post_data = qs.parse(body);

        // verify the checksum
        var checksumhash = post_data.CHECKSUMHASH;
        // delete post_data.CHECKSUMHASH;
        var result = checksum_lib.verifychecksum(post_data, config.PaytmConfig.key, checksumhash);


        // Send Server-to-Server request to verify Order Status
        var params = { "MID": config.PaytmConfig.mid, "ORDERID": post_data.ORDERID };

        checksum_lib.genchecksum(params, config.PaytmConfig.key, function (err, checksum) {

            params.CHECKSUMHASH = checksum;
            post_data = 'JsonData=' + JSON.stringify(params);

            var options = {
                hostname: 'securegw-stage.paytm.in',
                port: 443,
                path: '/merchant-status/getTxnStatus',
                method: 'POST',
                headers: {
                    'Content-Type': 'application/x-www-form-urlencoded',
                    'Content-Length': post_data.length
                }
            };

            // Set up the request
            var response = "";
            var post_req = https.request(options, function (post_res) {
                post_res.on('data', function (chunk) {
                    response += chunk;
                });

                post_res.on('end', function () {
                    var _result = JSON.parse(response);
                    if (_result.STATUS == 'TXN_SUCCESS') {
                        res.send('payment sucess')
                        res.redirect('/');
                    } else {
                        res.send('payment failed')
                        res.redirect('/paras');
                    }
                });
            });

            // post the data
            post_req.write(post_data);
            post_req.end();
        });
    });
});
app.post('/payment', (req, res) => {
    var paymentDetails = {
        amount: req.body.amount,
        customerId: req.body.id,
        customerEmail: req.body.email,
        customerPhone: req.body.phone
    }
    if (!paymentDetails.amount || !paymentDetails.customerId || !paymentDetails.customerEmail || !paymentDetails.customerPhone) {
        res.status(400).send('Payment failed')
    } else {
        var params = {};
        params['MID'] = config.PaytmConfig.mid;
        params['WEBSITE'] = config.PaytmConfig.website;
        params['CHANNEL_ID'] = 'WEB';
        params['INDUSTRY_TYPE_ID'] = 'Retail';
        params['ORDER_ID'] = 'TEST_001' + new Date().getTime();
        params['CUST_ID'] = paymentDetails.customerId;
        params['TXN_AMOUNT'] = paymentDetails.amount;
        params['CALLBACK_URL'] = 'http://localhost:3000/callback';
        params['EMAIL'] = paymentDetails.customerEmail;
        params['MOBILE_NO'] = paymentDetails.customerPhone;


        checksum_lib.genchecksum(params, config.PaytmConfig.key, function (err, checksum) {
            var txn_url = "https://securegw-stage.paytm.in/theia/processTransaction"; // for staging
             //var txn_url = "https://securegw.paytm.in/theia/processTransaction"; // for production

            var form_fields = "";
            for (var x in params) {
                form_fields += "<input type='hidden' name='" + x + "' value='" + params[x] + "' >";
            }
            form_fields += "<input type='hidden' name='CHECKSUMHASH' value='" + checksum + "' >";

            res.writeHead(200, { 'Content-Type': 'text/html' });
            res.write('<html><head><title>Merchant Checkout Page</title></head><body><center><h1>Please do not refresh this page...</h1></center><form method="post" action="' + txn_url + '" name="f1">' + form_fields + '</form><script type="text/javascript">document.f1.submit();</script></body></html>');
            res.end();
        });
    }

});

app.listen(3000, () => {
    console.log('connected')
})