using System;

using System.Web.Mvc;

using System.Collections.Generic;

using System.Security.Cryptography;

using System.Text;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

using System.Net.Http;

using System.Threading.Tasks;

using System.Net.Http.Headers;

​

namespace HelloWorldMvcApp

{

    public class HomeController : Controller

    {

        [HttpGet]

        public ActionResult Index()

        {

            return View(new SampleViewModel());

        }

​

        [HttpPost]

        public JsonResult GetAnswer(string question)

        {

            // Pre-generated access/secret keys

            var accessKey = "eiGuuO5adbR5QTK95a7U";

            var secretKey = "SKZV8lics/A5/ZgoZPhH6dhDEFjHjbr0qQV8DwKl";

            // Endpoint where the request will be sent to

            var endpoint = "https://api-services-connect.tunedglobal.com/api/v3/users/authenticateexternaluser";

            // Initialize authentication code

            var authCode = string.Empty;

            // Encode request url with UTF8 encoding table

            var uri = System.Web.HttpUtility.UrlEncode(endpoint, Encoding.UTF8);

            // Payload

            var data = new UserProfile

            {

                UserId = 32263556,

                Country = "TH"

            };

            // Serialize payload

            string serializedData = JsonConvert.SerializeObject(data);

            // Convert serialized payload to bytes using UTF8 encoding table

            byte[] content = Encoding.UTF8.GetBytes("{\"UserId\":32263556,\"Country\":\"TH\"}");

            // Hashing the request body using MD5 hashing algorithm, any change in request body will result in different hash

            MD5 md5 = MD5.Create();

            byte[] requestContentHash = md5.ComputeHash(content);

            // Convert hashed data to base 64 string

            string requestContentBase64String = Convert.ToBase64String(requestContentHash);

            // Generate timestamp using unix time

            DateTime epochStart = new DateTime(1970, 01, 01, 0, 0, 0, 0, DateTimeKind.Utc);

            TimeSpan timeSpan = DateTime.UtcNow - epochStart;

            string requestTimeStamp = Convert.ToUInt64(timeSpan.TotalSeconds).ToString();

            // Generate a random nonce for each request

            string nonce = Guid.NewGuid().ToString("N");

            // Signature raw data. Format: {your-access-key}{http-method}{request-url}{request-body-base64-string}{nonce}{timestamp}

            string signatureRawData = String.Format("{0}{1}{2}{3}{4}{5}", accessKey, "POST", uri, requestContentBase64String, nonce, requestTimeStamp);

            // Convert formatted signature raw data to bytes

            byte[] signature = Encoding.UTF8.GetBytes(signatureRawData);

            // Get secret key as bytes

            var secretKeyByteArray = Convert.FromBase64String(secretKey);

            // Initialize the keyed hash object

            using (HMACSHA256 sha = new HMACSHA256(secretKeyByteArray))

            {

                // Sign the request

                byte[] signatureBytes = sha.ComputeHash(signature);

                // Convert the result to base64 string

                string requestSignatureBase64String = Convert.ToBase64String(signatureBytes);

                // Generate authentication code. Format: {your-access-key}:{signature}:{nonce}:{timestamp}

                authCode = string.Format("{0}:{1}:{2}:{3}", accessKey, requestSignatureBase64String, nonce, requestTimeStamp);

            }

            return Json(authCode);

        }

    }

​

    public class UserProfile

    {

        public int UserId {get;set;}

        public string Country {get;set;}

    }

}