Paya Gateway - Node.js request

request.js

let crypto = require('crypto');
var https = require('follow-redirects').https;
var fs = require('fs');

var merchantId = '173859436515';
var merchantKey = 'P1J2V8P2Q3D8';
var clientId = 'W8yvKQ5XbvAn7dUDJeAnaWCEwA4yXEgd';
var clientSecret = 'iLzODV5AUsCGWGkr';

var host = 'https://api-cert.sagepayments.com';
var endpoint = '/bankcard/v1/charges';
var action = '?type=Authorization';
var url = host + endpoint + action;
var timestamp = Math.floor(new Date().getTime()/1000.0);
var nonce = timestamp;
console.log('timestamp: ' + timestamp);
console.log('');
var verb = 'POST';


var postData = JSON.stringify({
  "ecommerce": {
    "amounts": {
      "total": 1
    },
    "cardData": {
      "number": "4111111111111111",
      "expiration": "1230"
    },
    "orderNumber": "SDK" + timestamp
  }
});

var authString = verb + url + postData + merchantId + nonce + timestamp;
console.log('authString: ' + authString);
console.log('');

function computeHMAC(stringToBeHashed, key) {
  var hmac = crypto.createHmac("sha512", key);
  var hash = hmac.update(new Buffer.from(stringToBeHashed, 'utf-8')).digest("base64");
  return hash;
}

var authKey = computeHMAC(authString, clientSecret);
console.log('AuthKey: ' + authKey);
console.log('');


var options = {
  'method': verb,
  'hostname': 'api-cert.sagepayments.com',
  'path': endpoint + action,
  'headers': {
    'clientId': clientId,
    'merchantId': merchantId,
    'merchantKey': merchantKey,
    'nonce': nonce,
    'timestamp': timestamp,
    'Authorization': authKey,
    'Content-Type': 'application/json'
  },
  'maxRedirects': 20
};

console.log('Options: ' + JSON.stringify(options));
console.log('');

var req = https.request(options, function (res) {
  var chunks = [];

  res.on("data", function (chunk) {
    chunks.push(chunk);
  });

  res.on("end", function (chunk) {
    var body = Buffer.concat(chunks);
    console.log(body.toString());
    console.log('');
  });

  res.on("error", function (error) {
    console.error(error);
    console.log('');
  });
});

req.write(postData);

req.end();