Merchant to client to merchant round trip implemented (no security).

QRBee.Core/Data/ClientToMerchantResponse.cs

@@ -32,7 +32,25 @@
             set;
         }
 
-        public string AsString() => $"{Request.AsString()}|{ClientId}|{TimeStampUTC:O}";
+        public string AsString() => $"{ClientId}|{TimeStampUTC:O}|{Request.AsString()}";
+
+        public static ClientToMerchantResponse FromString(string input)
+        {
+            var s = input.Split('|');
+            if (s.Length != 3)
+            {
+                throw new ApplicationException("Expected 3 elements");
+            }
+
+            var res = new ClientToMerchantResponse()
+            {
+                Request = MerchantToClientRequest.FromString(string.Join("|", s.Skip(2))),
+                ClientId = s[0],
+                TimeStampUTC = DateTime.ParseExact(s[1], "O", null)
+            };
+
+            return res;
+        }
 
     }
 }

QRBee.Core/Data/MerchantToClientRequest.cs

@@ -1,4 +1,6 @@
-namespace QRBee.Core.Data
+using System.Globalization;
+
+namespace QRBee.Core.Data
 {
     public record MerchantToClientRequest
     {
@@ -32,7 +34,27 @@
             set;
         }
 
-        public string AsString() => $"{TransactionId}|{Name}|{Amount:0.00}|{TimeStampUTC:O}";
+        public string AsString() => $"{TransactionId}|{Name}|{Amount.ToString("0.00", CultureInfo.InvariantCulture)}|{TimeStampUTC:O}";
+
+        public static MerchantToClientRequest FromString(string input)
+        {
+            var s = input.Split('|');
+            if (s.Length != 4)
+            {
+                throw new ApplicationException("Expected 4 elements");
+            }
+
+            var res = new MerchantToClientRequest
+            {
+                TransactionId = s[0],
+                Name = s[1],
+                Amount = Convert.ToDecimal(s[2], CultureInfo.InvariantCulture),
+                TimeStampUTC = DateTime.ParseExact(s[3],"O",null)
+            };
+
+
+            return res;
+        }
 
     }
 }

QRBee/QRBee/ViewModels/ClientPageViewModel.cs

@@ -1,12 +1,116 @@
 using System;
-using System.Collections.Generic;
+using QRBee.Core.Data;
-using System.Text;
+using QRBee.Services;
+using QRBee.Views;
+using Xamarin.Forms;
 
 namespace QRBee.ViewModels
 {
-
+    internal class ClientPageViewModel: BaseViewModel
-
-    internal class ClientPageViewModel
     {
+        public bool _isVisible;
+        public string _amount;
+        private string _qrCode;
+        private MerchantToClientRequest _merchantToClientRequest;
+        private readonly ClientPage _clientPage;
+
+        public ClientPageViewModel(Views.ClientPage clientPage)
+        {
+            ScanCommand = new Command(OnScanButtonClicked);
+            GenerateQrCommand = new Command(OnGenerateQrClicked);
+            _clientPage = clientPage;
+        }
+
+        public Command ScanCommand
+        {
+            get;
+        }
+
+        public Command GenerateQrCommand 
+        { 
+            get; 
+        }
+
+        private async void OnScanButtonClicked(object sender)
+        {
+            try
+            {
+                var scanner = DependencyService.Get<IQRScanner>();
+                var result = await scanner.ScanQR();
+                if (result != null)
+                {
+                    _merchantToClientRequest = MerchantToClientRequest.FromString(result);
+                    Amount = $"{_merchantToClientRequest.Amount:N2}";
+                    IsVisible = true;
+                }
+            }
+            catch (Exception ex)
+            {
+                throw;
+            }
+        }
+
+        public string Amount
+        {
+            get => _amount;
+            set
+            {
+                if (value == _amount)
+                {
+                    return;
+                }
+                _amount = value;
+                OnPropertyChanged(nameof(Amount));
+            }
+        }
+
+        public bool IsVisible
+        {
+            get => _isVisible;
+            set
+            {
+                if (value == _isVisible)
+                {
+                    return;
+                }
+                _isVisible = value;
+                OnPropertyChanged(nameof(IsVisible));
+            }
+        }
+
+        public string QrCode
+        {
+            get => _qrCode;
+            set
+            {
+                // _qrCode = $"{Amount}/{Name}";
+                if (_qrCode == value)
+                    return;
+
+                _qrCode = value;
+                OnPropertyChanged(nameof(QrCode));
+            }
+        }
+
+        public async void OnGenerateQrClicked(object obj)
+        {
+
+            bool answer = await _clientPage.DisplayAlert("Confirmation", "Would you like to accept the offer?", "Yes", "No");
+            if (answer)
+            {
+                var response = new ClientToMerchantResponse
+                {
+                    ClientId = Guid.NewGuid().ToString("D"),
+                    TimeStampUTC = DateTime.UtcNow,
+                    Request = _merchantToClientRequest
+                    
+                };
+                // TODO Create merchant signature.
+                QrCode = response.AsString();
+            }
+
+            
+        }
+
     }
 }

QRBee/QRBee/ViewModels/MerchantPageViewModel.cs

@@ -1,21 +1,43 @@
 using System;
+using QRBee.Core.Data;
+using QRBee.Services;
 using Xamarin.Forms;
 
 namespace QRBee.ViewModels
 {
     internal class MerchantPageViewModel : BaseViewModel
     {
+        private bool _isVisible;
         private string _name;
         private decimal _amount;
         private string _qrCode;
 
         public Command GenerateQrCommand { get; }
+        public Command ScanCommand{ get; }
 
         public MerchantPageViewModel()
         {
+            ScanCommand = new Command(OnScanButtonClicked);
             GenerateQrCommand = new Command(OnGenerateQrClicked);
         }
 
+        private async void OnScanButtonClicked(object sender)
+        {
+            try
+            {
+                var scanner = DependencyService.Get<IQRScanner>();
+                var result = await scanner.ScanQR();
+                if (result != null)
+                {
+
+                }
+            }
+            catch (Exception ex)
+            {
+                throw;
+            }
+        }
+
         public string Name
         {
             get => _name;
@@ -42,6 +64,20 @@ namespace QRBee.ViewModels
             }
         }
 
+        public bool IsVisible
+        {
+            get => _isVisible;
+            set
+            {
+                if (value == _isVisible)
+                {
+                    return;
+                }
+                _isVisible = value;
+                OnPropertyChanged(nameof(IsVisible));
+            }
+        }
+
         public string QrCode
         {
             get => _qrCode;
@@ -58,9 +94,16 @@ namespace QRBee.ViewModels
 
         public async void OnGenerateQrClicked(object obj)
         {
-            QrCode = $"{Name}.{Amount:0.00}.{DateTime.UtcNow:O}";
+            var trans = new MerchantToClientRequest
-            // Prefixing with `//` switches to a different navigation stack instead of pushing to the active one
+            {
-            // await Shell.Current.GoToAsync($"//{nameof(AboutPage)}");
+                TransactionId = Guid.NewGuid().ToString("D"),
+                Name = Name,
+                Amount = Amount,
+                TimeStampUTC = DateTime.UtcNow
+            };
+            // TODO Create merchant signature.
+            QrCode = trans.AsString();
+            IsVisible = true;
         }
 
     }

QRBee/QRBee/Views/ClientPage.xaml

@@ -1,6 +1,10 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:viewmodels="clr-namespace:QRBee.ViewModels"
+             xmlns:forms="clr-namespace:ZXing.Net.Mobile.Forms;assembly=ZXing.Net.Mobile.Forms"
+             xmlns:common="clr-namespace:ZXing.Common;assembly=zxing.portable"
+             x:DataType="viewmodels:ClientPageViewModel"
              x:Class="QRBee.Views.ClientPage">
     <ContentPage.Content>
         <StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
@@ -9,13 +13,28 @@
             <!--     HorizontalOptions="CenterAndExpand" /> -->
             <StackLayout Orientation="Vertical" VerticalOptions="FillAndExpand">
                 <StackLayout Orientation="Vertical">
-                    <Label x:Name="Name" VerticalOptions="FillAndExpand" Text="Merchant name: "/>
+                    <Label VerticalOptions="FillAndExpand" Text="Amount:"/>
-                    <Label x:Name="Amount" VerticalOptions="FillAndExpand" Text="Amount: "/>
+                    <Label VerticalOptions="FillAndExpand" Text="{Binding Amount}"/>
-                </StackLayout>
                 </StackLayout>
 
-            <StackLayout Orientation="Horizontal" VerticalOptions="End" Margin="0,0,0,10">
+                <forms:ZXingBarcodeImageView
-                <Button  Text="Scan me" HorizontalOptions="CenterAndExpand" BackgroundColor="Aqua" TextColor="Red" Clicked="OnScanButtonClicked"/>
+                    BarcodeFormat="QR_CODE"
+                    BarcodeValue="{Binding QrCode}"
+                    HorizontalOptions="FillAndExpand"
+                    VerticalOptions="FillAndExpand">
+                    <forms:ZXingBarcodeImageView.BarcodeOptions>
+                        <common:EncodingOptions Width="300" Height="300" />
+                    </forms:ZXingBarcodeImageView.BarcodeOptions>
+                </forms:ZXingBarcodeImageView>
+
+            </StackLayout>
+            
+            <StackLayout Orientation="Vertical" VerticalOptions="End" Margin="0,0,0,10">
+                <StackLayout Orientation="Horizontal">
+                    <Button  Text="Accept" HorizontalOptions="FillAndExpand" BackgroundColor="DarkGreen" IsVisible="{Binding IsVisible}" Command="{Binding GenerateQrCommand}"/>
+                    <Button  Text="Deny" HorizontalOptions="FillAndExpand" BackgroundColor="DarkRed" IsVisible="{Binding IsVisible}"/>
+                </StackLayout>
+                <Button  Text="Scan me" HorizontalOptions="FillAndExpand" BackgroundColor="Aqua" TextColor="Red" Command="{Binding ScanCommand}"/>
             </StackLayout>
 
         </StackLayout>

QRBee/QRBee/Views/ClientPage.xaml.cs

@@ -1,5 +1,6 @@
 using System;
 using QRBee.Services;
+using QRBee.ViewModels;
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
 
@@ -11,25 +12,7 @@ namespace QRBee.Views
         public ClientPage()
         {
             InitializeComponent();
-        }
+            this.BindingContext = new ClientPageViewModel(this);
-
-        private async void OnScanButtonClicked(object sender, EventArgs args)
-        {
-            try
-            {
-                var scanner = DependencyService.Get<IQRScanner>();
-                var result = await scanner.ScanQR();
-                if (result != null)
-                {
-                    Name.Text = result;
-                    Amount.Text = result;
-                }
-            }
-            catch (Exception ex)
-            {
-
-                throw;
-            }
         }
     }
 }

QRBee/QRBee/Views/MerchantPage.xaml

@@ -23,9 +23,6 @@
                 <!-- -->
                 <!-- </StackLayout> -->
                 <!-- -->
-                <!-- <StackLayout Orientation="Horizontal"> -->
-                <!-- -->
-                <!-- </StackLayout> -->
 
                 <forms:ZXingBarcodeImageView
                     BarcodeFormat="QR_CODE"
@@ -40,9 +37,9 @@
             </StackLayout>
 
 
-
+            <StackLayout Orientation="Vertical" VerticalOptions="End" Margin="0,0,0,10">
-            <StackLayout Orientation="Horizontal" VerticalOptions="End" Margin="0,0,0,10">
+                <Button  Text="Scan response" HorizontalOptions="FillAndExpand" BackgroundColor="Aqua" TextColor="Red" IsVisible="{Binding IsVisible}" Command="{Binding ScanCommand}"/>
-                <Button Text="Generate QR code" HorizontalOptions="CenterAndExpand" BackgroundColor="Red" TextColor="Aqua" Command="{Binding GenerateQrCommand}"/>
+                <Button Text="Generate QR code" HorizontalOptions="FillAndExpand" BackgroundColor="Red" TextColor="Aqua" Command="{Binding GenerateQrCommand}"/>
             </StackLayout>