Work on Transaction started. Pre-checks complete.

QRBee.Core/Client/Client.cs

@@ -207,18 +207,18 @@ namespace QRBee.Core.Client
 
         /// <returns>Success</returns>
         /// <exception cref="ApiException">A server side error occurred.</exception>
-        public virtual System.Threading.Tasks.Task InsertTransactionAsync(PaymentRequest body)
+        public virtual System.Threading.Tasks.Task<PaymentResponse> PayAsync(PaymentRequest body)
         {
-            return InsertTransactionAsync(body, System.Threading.CancellationToken.None);
+            return PayAsync(body, System.Threading.CancellationToken.None);
         }
 
         /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
         /// <returns>Success</returns>
         /// <exception cref="ApiException">A server side error occurred.</exception>
-        public virtual async System.Threading.Tasks.Task InsertTransactionAsync(PaymentRequest body, System.Threading.CancellationToken cancellationToken)
+        public virtual async System.Threading.Tasks.Task<PaymentResponse> PayAsync(PaymentRequest body, System.Threading.CancellationToken cancellationToken)
         {
             var urlBuilder_ = new System.Text.StringBuilder();
-            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/api/QRBee/InsertTransaction");
+            urlBuilder_.Append(BaseUrl != null ? BaseUrl.TrimEnd('/') : "").Append("/api/QRBee/Pay");
 
             var client_ = _httpClient;
             var disposeClient_ = false;
@@ -230,6 +230,7 @@ namespace QRBee.Core.Client
                     content_.Headers.ContentType = System.Net.Http.Headers.MediaTypeHeaderValue.Parse("application/json");
                     request_.Content = content_;
                     request_.Method = new System.Net.Http.HttpMethod("POST");
+                    request_.Headers.Accept.Add(System.Net.Http.Headers.MediaTypeWithQualityHeaderValue.Parse("text/plain"));
 
                     PrepareRequest(client_, request_, urlBuilder_);
 
@@ -254,7 +255,12 @@ namespace QRBee.Core.Client
                         var status_ = (int)response_.StatusCode;
                         if (status_ == 200)
                         {
-                            return;
+                            var objectResponse_ = await ReadObjectResponseAsync<PaymentResponse>(response_, headers_, cancellationToken).ConfigureAwait(false);
+                            if (objectResponse_.Object == null)
+                            {
+                                throw new ApiException("Response was null which was not expected.", status_, objectResponse_.Text, headers_, null);
+                            }
+                            return objectResponse_.Object;
                         }
                         else
                         {

QRBee.Core/Data/ClientCardData.cs

@@ -15,7 +15,36 @@
         /// WARNING: this should always be encrypted and never transmitted in clear text form.
         /// </summary>
         /// <returns>Converted string</returns>
-        public string AsString() => $"{TransactionId}|{CardNumber}|{ExpirationDateMMYY}|{ValidFrom}|{CardHolderName}|{CVC}|{IssueNo}";
+        public string AsString() => $"{TransactionId}|{CardNumber}|{ExpirationDateMMYY}|{ValidFrom}|{CardHolderName}|{CVC}|{IssueNo ?? 0}";
+
+        public static ClientCardData FromString(string input)
+        {
+            var s = input.Split('|');
+            if (s.Length < 7)
+            {
+                throw new ApplicationException("Expected 7 or more elements");
+            }
+
+            var res = new ClientCardData()
+            {
+                TransactionId = s[0],
+                CardNumber = s[1],
+                ExpirationDateMMYY = s[2],
+                ValidFrom = s[3],
+                CardHolderName = s[4],
+                CVC = s[5]
+            };
+
+            if (!string.IsNullOrWhiteSpace(s[6]))
+                res.IssueNo = Convert.ToInt32(s[6]);
+
+            if (res.IssueNo <= 0)
+            {
+                res.IssueNo = null;
+            }
+
+            return res;
+        }
 
     }
 }

QRBee/QRBee.Android/MainActivity.cs

@@ -30,16 +30,10 @@ namespace QRBee.Droid
             LoadApplication(new App(AddServices));
             ZXing.Mobile.MobileBarcodeScanner.Initialize(Application);
 
-            if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.Camera) == (int) Permission.Granted)
+            if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.Camera) != (int) Permission.Granted)
             {
-                
+                ActivityCompat.RequestPermissions(this, new String[] {Manifest.Permission.Camera}, 0);
             }
-            else
-            {
-                ActivityCompat.RequestPermissions(this, new String[] { Manifest.Permission.Camera }, 0);
-                // ActivityCompat.RequestPermissions(this, new String[] { Manifest.Permission.UseFingerprint }, 0);
-            }
-
         }
 
         public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)

QRBee/QRBee/ViewModels/MerchantPageViewModel.cs

@@ -48,8 +48,9 @@ namespace QRBee.ViewModels
                 //QrCode = null;
                 IsVisible = false;
 
-                await service.InsertTransactionAsync(paymentRequest);
+                var response = await service.PayAsync(paymentRequest);
 
+                //TODO handle response
                 await Application.Current.MainPage.DisplayAlert("Success", "The transaction completed successfully ", "Ok");
             }
             catch (Exception e)

QRBeeApi/Controllers/QRBeeController.cs

@@ -35,11 +35,11 @@ namespace QRBee.Api.Controllers
             return _service.Update(clientId,value);
         }
 
-        [HttpPost("InsertTransaction")]
+        [HttpPost("Pay")]
-        public Task InsertTransaction([FromBody] PaymentRequest value)
+        public Task<PaymentResponse> Pay([FromBody] PaymentRequest value)
         {
             _logger.LogInformation($"Trying to insert new transaction {value.ClientResponse.MerchantRequest.MerchantTransactionId}");
-            return _service.InsertTransaction(value);
+            return _service.Pay(value);
         }
     }
 }

QRBeeApi/Services/Database/IStorage.cs

@@ -31,6 +31,13 @@
         /// <param name="info">Information to be inserted</param>
         Task PutTransactionInfo(TransactionInfo info);
 
+        /// <summary>
+        /// Retrieve transaction information from database
+        /// </summary>
+        /// <param name="id">Identifier by which transaction information will be retrieved</param>
+        /// <returns>Transaction information</returns>
+        Task<TransactionInfo> GetTransactionInfoByTransactionId(string id);
+
         /// <summary>
         /// Inserts CertificateInfo into database
         /// </summary>
@@ -43,6 +50,13 @@
         /// </summary>
         /// <param name="id">Identifier by which certificate information will be retrieved</param>
         /// <returns>Certificate information</returns>
-        Task<CertificateInfo> GetCertificateInfo(string id);
+        Task<CertificateInfo> GetCertificateInfoByCertificateId(string id);
+
+        /// <summary>
+        /// Retrieve certificate information from database
+        /// </summary>
+        /// <param name="clientId">Identifier by which certificate information will be retrieved</param>
+        /// <returns>Certificate information</returns>
+        Task<CertificateInfo> GetCertificateInfoByUserId(string clientId);
     }
 }

QRBeeApi/Services/Database/Storage.cs

@@ -102,6 +102,12 @@ namespace QRBee.Api.Services.Database
             return cursor.Current.FirstOrDefault();
         }
 
+        public async Task<TransactionInfo> GetTransactionInfoByTransactionId(string id)
+        {
+            var transaction = await TryGetTransactionInfo(id);
+            return transaction ?? throw new ApplicationException($"Transaction with Id: {id} not found.");
+        }
+
         public async Task InsertCertificate(CertificateInfo info)
         {
             var collection = _database.GetCollection<CertificateInfo>("Certificates");
@@ -131,7 +137,7 @@ namespace QRBee.Api.Services.Database
         /// <returns>null if certificate doesn't exist or CertificateInfo</returns>
         private async Task<CertificateInfo?> TryGetCertificateInfo(string id)
         {
-            var collection = _database.GetCollection<CertificateInfo>("Transactions");
+            var collection = _database.GetCollection<CertificateInfo>("Certificates");
             using var cursor = await collection.FindAsync($"{{ Id: \"{id}\" }}");
             if (!await cursor.MoveNextAsync())
             {
@@ -141,10 +147,23 @@ namespace QRBee.Api.Services.Database
             return cursor.Current.FirstOrDefault();
         }
 
-        public async Task<CertificateInfo> GetCertificateInfo(string id)
+        public async Task<CertificateInfo> GetCertificateInfoByCertificateId(string id)
         {
             var certificate = await TryGetCertificateInfo(id);
             return certificate ?? throw new ApplicationException($"Certificate with Id: {id} not found.");
         }
+
+        public async Task<CertificateInfo> GetCertificateInfoByUserId(string clientId)
+        {
+            var collection = _database.GetCollection<CertificateInfo>("Certificates");
+            using var cursor = await collection.FindAsync($"{{ ClientId: \"{clientId}\" }}");
+            if (!await cursor.MoveNextAsync())
+            {
+                throw new ApplicationException($"Certificate with ClientId: {clientId} not found.");
+            }
+
+            return cursor.Current.FirstOrDefault() ?? throw new ApplicationException($"Certificate with ClientId: {clientId} not found.");
+        }
+
     }
 }

QRBeeApi/Services/Database/TransactionInfo.cs

@@ -34,5 +34,12 @@ namespace QRBee.Api.Services.Database
 
         public PaymentRequest Request { get; set; }
 
+        public enum TransactionStatus
+        {
+            Pending = 0,
+            Rejected = 1,
+            Succeeded = 2,
+        }
+        public TransactionStatus Status { get; set; } = TransactionStatus.Pending;
     }
 }

QRBeeApi/Services/IQRBeeAPI.cs

@@ -28,7 +28,7 @@ namespace QRBee.Api.Services
         /// Handles InsertTransaction request
         /// </summary>
         /// <param name="value">Payment request</param>
-        Task InsertTransaction(PaymentRequest value);
+        Task<PaymentResponse> Pay(PaymentRequest value);
 
     }
 }

QRBeeApi/Services/QRBeeAPIService.cs

@@ -45,7 +45,7 @@ namespace QRBee.Api.Services
         public async Task<RegistrationResponse> Register(RegistrationRequest request)
         {
 
-            Validate(request);
+            ValidateRegistration(request);
 
             var info = Convert(request);
 
@@ -69,18 +69,11 @@ namespace QRBee.Api.Services
 
         public Task Update(string clientId, RegistrationRequest request)
         {
-            Validate(request);
+            ValidateRegistration(request);
             var info = Convert(request);
             return _storage.UpdateUser(info);
         }
-
+        private void ValidateRegistration(RegistrationRequest request)
-        public Task InsertTransaction(PaymentRequest value)
-        {
-            var info = Convert(value);
-            return _storage.PutTransactionInfo(info);
-        }
-
-        private void Validate(RegistrationRequest request)
         {
             if (request == null)
             {
@@ -92,14 +85,14 @@ namespace QRBee.Api.Services
             var dateOfBirth = request.DateOfBirth;
             var certificateRequest = request.CertificateRequest;
 
-            if (string.IsNullOrEmpty(name) || name.All(char.IsLetter)==false || name.Length>=MaxNameLength)
+            if (string.IsNullOrEmpty(name) || name.All(char.IsLetter) == false || name.Length >= MaxNameLength)
             {
                 throw new ApplicationException($"Name \"{name}\" isn't valid");
             }
 
             var freq = Regex.Matches(email, @"[^@]+@[^@]+").Count;
 
-            if (string.IsNullOrEmpty(email) || email.IndexOf('@')<0 || freq>=2 || email.Length >= MaxEmailLength)
+            if (string.IsNullOrEmpty(email) || email.IndexOf('@') < 0 || freq >= 2 || email.Length >= MaxEmailLength)
             {
                 throw new ApplicationException($"Email \"{email}\" isn't valid");
             }
@@ -130,6 +123,105 @@ namespace QRBee.Api.Services
             }
         }
 
+        public async Task<PaymentResponse> Pay(PaymentRequest value)
+        {
+            //1. Check payment request parameters for validity
+            ValidateTransaction(value);
+
+            //2. Check client signature
+            var t2 = CheckSignature(
+                value.ClientResponse.AsDataForSignature(),
+                value.ClientResponse.ClientSignature,
+                value.ClientResponse.ClientId);
+
+            //3. Check merchant signature
+            var t3 = CheckSignature(
+                value.ClientResponse.MerchantRequest.AsDataForSignature(),
+                value.ClientResponse.MerchantRequest.MerchantSignature,
+                value.ClientResponse.MerchantRequest.MerchantId);
+
+            //4. Check if transaction was already processed
+            var t4 = CheckTransaction(value.ClientResponse.MerchantRequest.MerchantTransactionId);
+
+            //Parallel task execution
+            await Task.WhenAll(t2, t3, t4);
+
+            //5. Decrypt client card data
+            var clientCardData = DecryptClientData(value.ClientResponse.EncryptedClientCardData);
+
+            //6. Check client card data for validity
+            //7. Register preliminary transaction record with expiry of one minute
+            //8. Send client card data to a payment gateway
+            //9. Record transaction with result
+            //10. Make response for merchant
+            var info = Convert(value);
+            await _storage.PutTransactionInfo(info);
+            return new PaymentResponse();
+        }
+
+        private void ValidateTransaction(PaymentRequest request)
+        {
+            if (request == null)
+            {
+                throw new NullReferenceException();
+            }
+
+            var clientId = request.ClientResponse.ClientId;
+            var merchantId = request.ClientResponse.MerchantRequest.MerchantId;
+            var transactionId = request.ClientResponse.MerchantRequest.MerchantTransactionId;
+            var amount = request.ClientResponse.MerchantRequest.Amount;
+
+            if (clientId == null || merchantId == null || transactionId == null)
+            {
+                throw new ApplicationException("Id isn't valid");
+            }
+
+            if (amount is <= 0 or >= 10000)
+            {
+                throw new ApplicationException($"Amount \"{amount}\" isn't valid");
+            }
+        }
+
+        private async Task CheckSignature(string data,string signature, string id)
+        {
+            var info = await _storage.GetCertificateInfoByUserId(id);
+            var certificate = _securityService.Deserialize(info.Certificate);
+
+            var check = _securityService.Verify(
+                Encoding.UTF8.GetBytes(data),
+                System.Convert.FromBase64String(signature),
+                certificate);
+            
+            if (!check)
+            {
+                throw new ApplicationException($"Signature is incorrect for Id: {id}.");
+            }
+        }
+
+        private async Task CheckTransaction(string transactionId)
+        {
+            var info = await _storage.GetTransactionInfoByTransactionId(transactionId);
+            switch (info.Status)
+            {
+                case TransactionInfo.TransactionStatus.Succeeded:
+                    throw new ApplicationException($"Transaction with Id: {transactionId} was already made.");
+                case TransactionInfo.TransactionStatus.Rejected:
+                    throw new ApplicationException($"Transaction with Id: {transactionId} is not valid.");
+                case TransactionInfo.TransactionStatus.Pending:
+                    throw new ApplicationException($"Transaction with Id: {transactionId} is already in progress.");
+                default:
+                    return;
+            }
+        }
+
+        private ClientCardData DecryptClientData(string encryptedClientCardData)
+        {
+            var info = System.Convert.FromBase64String(encryptedClientCardData);
+            var bytes = _securityService.Decrypt(info);
+            var s = Encoding.UTF8.GetString(bytes);
+            return ClientCardData.FromString(s);
+        }
+
         private static RSA LoadRsaPublicKey(StringRSAParameters stringParameters)
         {
             var rsaParameters = new RSAParameters