Minor refactoring + unit tests added

PriceChecker.Core/Services/PriceSeeker.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using System.Text.RegularExpressions;
 using System.Threading;
@@ -37,14 +38,23 @@ public async Task<PriceSeekResult[]> SeekAsync(Product product, CancellationToke
             });
 
             return await Task.WhenAll(result)
-                .ContinueWith(x => x.Result?.Where(x => x != null).ToArray() ?? new PriceSeekResult[0]);
+                .ContinueWith(x => x.Result?.Where(x => x != null).ToArray() ?? new PriceSeekResult[0], TaskContinuationOptions.OnlyOnRanToCompletion);
         }
 
         private async Task<PriceSeekResult> Seek(ProductSource productSource, CancellationToken cancel)
         {
             var agent = productSource.Agent;
             var url = string.Format(agent.Url, productSource.AgentArgument);
-            var content = await _trickyHttpClient.DownloadContent(url, cancel);
+            string content;
+            try
+            {
+                content = await _trickyHttpClient.DownloadContent(url, cancel);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, $"Failed loading content for source `{productSource.AgentId}`, url = `{url}`");
+                throw;
+            }
             if (content == null)
                 return null;
 

PriceChecker.Infrastructure/Events/EventBus.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Concurrent;
 using System.Reactive;
 using System.Reactive.Linq;
 

PriceChecker.UI.Forms/AutoGrid/AttachingBehavior.cs

@@ -57,7 +57,7 @@ private void OnItemsSourceChanged(object sender, EventArgs e)
             }
 
             if (AssociatedObject.SelectionMode == DataGridSelectionMode.Extended &&
-                typeof(ISelectable).IsAssignableFrom(GetItemType()))
+                typeof(ISelectable).IsAssignableFrom(Helpers.GetListItemType(AssociatedObject.ItemsSource)))
             {
                 BindIsSelected();
             }
@@ -118,15 +118,5 @@ private void BindIsSelected()
             rowStyle.Setters.Add(new Setter(DataGrid.IsSelectedProperty, binding));
             AssociatedObject.RowStyle = rowStyle;
         }
-
-        private Type GetItemType()
-        {
-            var sourceCollection = AssociatedObject.ItemsSource;
-            if (sourceCollection is ListCollectionView listCollectionView)
-            {
-                sourceCollection = listCollectionView.SourceCollection;
-            }
-            return sourceCollection.GetType().GetGenericArguments().Single();
-        }
     }
 }

PriceChecker.UI.Forms/AutoGrid/Properties.cs

@@ -30,9 +30,9 @@ public static IEnumerable GetItemsSource(DependencyObject element)
             return (IEnumerable) element.GetValue(ItemsSourceProperty);
         }
 
-        public static void ItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        private static void ItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
-            var itemType = e.NewValue.GetType().GetGenericArguments().Single();
+            var itemType = Helpers.GetListItemType(e.NewValue);
             var properties = itemType.GetProperties();
             var groupByProps = properties
                 .Where(x => x.GetCustomAttributes(false).OfType<GroupByAttribute>().Any())

PriceChecker.UI.Forms/Helpers.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Windows.Data;
+
+namespace Genius.PriceChecker.UI.Forms
+{
+    internal class Helpers
+    {
+        public static Type GetListItemType(object value)
+        {
+            if (value is ListCollectionView listCollectionView)
+                value = listCollectionView.SourceCollection;
+
+            if (value is ITypedObservableList typedObservableList)
+                return typedObservableList.ItemType;
+
+            return value.GetType().GetGenericArguments().Single();
+        }
+
+        public static string MakeCaptionFromPropertyName(string propertyName)
+        {
+            return Regex.Replace(propertyName, @"(?<=[^$])([A-Z])", " $1");
+        }
+    }
+}

PriceChecker.UI.Forms/TypedObservableList.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+
+namespace Genius.PriceChecker.UI.Forms
+{
+    public interface ITypedObservableList
+    {
+        Type ItemType { get; }
+    }
+
+    public class TypedObservableList<TContract, TType> : ObservableCollection<TContract>, ITypedObservableList, ITypedList
+    {
+        public PropertyDescriptorCollection GetItemProperties(PropertyDescriptor[] listAccessors)
+        {
+            return TypeDescriptor.GetProperties(typeof(TType));
+        }
+
+        public string GetListName(PropertyDescriptor[] listAccessors)
+        {
+            return null;
+        }
+
+        public Type ItemType => typeof(TType);
+    }
+}

PriceChecker.UI.Forms/ViewModels/TabViewModelBase.cs

@@ -2,7 +2,7 @@
 
 namespace Genius.PriceChecker.UI.Forms.ViewModels
 {
-    public interface ITabViewModel
+    public interface ITabViewModel : IViewModel
     {
         IActionCommand Activated { get; }
         IActionCommand Deactivated { get; }

PriceChecker.UI.Forms/ViewModels/ViewModelBase.cs

@@ -12,13 +12,17 @@
 
 namespace Genius.PriceChecker.UI.Forms.ViewModels
 {
-    public abstract class ViewModelBase : INotifyPropertyChanged, INotifyDataErrorInfo
+  public interface IViewModel : INotifyPropertyChanged, INotifyDataErrorInfo
+    {
+        bool TryGetPropertyValue(string propertyName, out object value);
+    }
+
+    public abstract class ViewModelBase : IViewModel
     {
         protected readonly ConcurrentDictionary<string, object> _propertyBag = new();
         private readonly Dictionary<string, List<ValidationRule>> _validationRules = new();
         private readonly Dictionary<string, List<string>> _errors = new();
-
-        protected bool PropertiesAreInitialized = false;
+        private bool _suspendDirtySet = false;
 
         public ViewModelBase()
         {
@@ -34,11 +38,29 @@ public IEnumerable GetErrors(string propertyName)
                 new List<string>();
         }
 
-        internal bool TryGetPropertyValue(string propertyName, out object value)
+        public bool TryGetPropertyValue(string propertyName, out object value)
         {
             return _propertyBag.TryGetValue(propertyName, out value);
         }
 
+        protected void InitializeProperties(Action action)
+        {
+            _suspendDirtySet = true;
+            try
+            {
+                action();
+
+                if (this is IHasDirtyFlag hasDirtyFlag)
+                {
+                    hasDirtyFlag.IsDirty = false;
+                }
+            }
+            finally
+            {
+                _suspendDirtySet = false;
+            }
+        }
+
         protected T GetOrDefault<T>(T defaultValue = default(T), [CallerMemberName] string name = null)
         {
             if (name == null)
@@ -74,9 +96,9 @@ protected void RaiseAndSetIfChanged<T>(T value, Action<T, T> valueChangedHandler
             _propertyBag.AddOrUpdate(name, _ => value, (_, __) => value);
             OnPropertyChanged(name);
 
-            if (this is IHasDirtyFlag hasDirtyFlag &&
+            if (!_suspendDirtySet &&
+                this is IHasDirtyFlag hasDirtyFlag &&
                 name != nameof(IHasDirtyFlag.IsDirty) &&
-                PropertiesAreInitialized &&
                 (this is not ISelectable || name != nameof(ISelectable.IsSelected)))
             {
                 hasDirtyFlag.IsDirty = true;

PriceChecker.UI.Forms/ViewModels/ViewModelExtensions.cs

@@ -8,14 +8,14 @@ namespace Genius.PriceChecker.UI.Forms.ViewModels
     public static class ViewModelExtensions
     {
         public static IDisposable WhenChanged<TViewModel, TProperty>(this TViewModel viewModel, Expression<Func<TViewModel, TProperty>> propertyAccessor, Action<TProperty> handler)
-            where TViewModel : ViewModelBase
+            where TViewModel : IViewModel
         {
             var propName = ExpressionHelpers.GetPropertyName(propertyAccessor);
 
             return WhenChanged(viewModel, propName, handler);
         }
 
-        public static IDisposable WhenChanged<TProperty>(this ViewModelBase viewModel, string propertyName, Action<TProperty> handler)
+        public static IDisposable WhenChanged<TProperty>(this IViewModel viewModel, string propertyName, Action<TProperty> handler)
         {
             PropertyChangedEventHandler fn = (_, args) =>
             {

PriceChecker.UI.Forms/WpfHelpers.cs

@@ -34,7 +34,7 @@ public static void AddFlyout<T>(FrameworkElement owner, string isOpenBindingPath
 
         public static DataGridTemplateColumn CreateButtonColumn(string commandPath, string iconName)
         {
-            var caption = commandPath.Replace("Command", "");
+            var caption = Helpers.MakeCaptionFromPropertyName(commandPath.Replace("Command", ""));
 
             var buttonFactory = new FrameworkElementFactory(typeof(Button));
             buttonFactory.SetBinding(Button.CommandProperty, new Binding(commandPath));

PriceChecker.UI.Tests/Helpers/TrackerScanContextTests.cs

@@ -0,0 +1,137 @@
+using System;
+using System.Reactive.Subjects;
+using AutoFixture;
+using Genius.PriceChecker.Core.Messages;
+using Genius.PriceChecker.Core.Models;
+using Genius.PriceChecker.UI.Helpers;
+using Xunit;
+
+namespace Genius.PriceChecker.UI.Tests.Helpers
+{
+  public class TrackerScanContextTests : TestBase
+    {
+        private readonly Fixture _fixture = new();
+        private readonly TrackerScanContext _sut;
+
+        // Session values:
+        private readonly Subject<ProductAutoScanStartedEvent> _productAutoScanStartedEventSubject;
+        private TrackerScanStatus? _lastStatus = null;
+        private double? _lastProgress = null;
+
+        public TrackerScanContextTests()
+        {
+            _productAutoScanStartedEventSubject = CreateEventSubject<ProductAutoScanStartedEvent>();
+
+            _sut = new TrackerScanContext(EventBusMock.Object);
+
+            _sut.ScanProgress.Subscribe(x => {
+                _lastStatus = x.Status;
+                _lastProgress = x.Progress;
+            });
+        }
+
+        [Fact]
+        public void NotifyStarted__Resets_state_and_calculates_initial_progress()
+        {
+            // Arrange
+            var count = 10;
+
+            // Act
+            _sut.NotifyStarted(count);
+
+            // Verify
+            var expectedProgress = 1d / (count * 2);
+            Assert.True(_sut.IsStarted);
+            Assert.False(_sut.HasErrors);
+            Assert.False(_sut.HasNewLowestPrice);
+            Assert.Equal(0, _sut.FinishedJobs);
+            Assert.Equal(TrackerScanStatus.InProgress, _lastStatus);
+            Assert.Equal(expectedProgress, _lastProgress);
+        }
+
+        [Fact]
+        public void NotifyProgressChange__When_ScannedOk__Increases_progress()
+        {
+            // Arrange
+            var count = 2;
+            _sut.NotifyStarted(count);
+
+            // Act
+            _sut.NotifyProgressChange(ProductScanStatus.ScannedOk);
+
+            // Verify
+            var expectedProgress = 0.5d; // 50% of 2 jobs
+            Assert.True(_sut.IsStarted);
+            Assert.False(_sut.HasErrors);
+            Assert.False(_sut.HasNewLowestPrice);
+            Assert.Equal(1, _sut.FinishedJobs);
+            Assert.Equal(TrackerScanStatus.InProgress, _lastStatus);
+            Assert.Equal(expectedProgress, _lastProgress);
+        }
+
+        [Fact]
+        public void NotifyProgressChange__When_scanned_last_job__Finishes_progress()
+        {
+            // Arrange
+            _sut.NotifyStarted(2);
+
+            // Act
+            _sut.NotifyProgressChange(ProductScanStatus.ScannedOk);
+            _sut.NotifyProgressChange(ProductScanStatus.ScannedOk);
+
+            // Verify
+            Assert.False(_sut.IsStarted);
+            Assert.False(_sut.HasErrors);
+            Assert.False(_sut.HasNewLowestPrice);
+            Assert.Equal(2, _sut.FinishedJobs);
+            Assert.Equal(TrackerScanStatus.Finished, _lastStatus);
+            Assert.Equal(1, _lastProgress);
+        }
+
+        [Fact]
+        public void NotifyProgressChange__When_ScannedWithErrors__Reports_about_errors()
+        {
+            // Arrange
+            _sut.NotifyStarted(_fixture.Create<int>());
+
+            // Act
+            _sut.NotifyProgressChange(ProductScanStatus.ScannedWithErrors);
+
+            // Verify
+            Assert.True(_sut.HasErrors);
+            Assert.Equal(TrackerScanStatus.InProgressWithErrors, _lastStatus);
+        }
+
+        [Fact]
+        public void NotifyProgressChange__When_ScannedNewLowest__Reports_about_new_lowest()
+        {
+            // Arrange
+            _sut.NotifyStarted(_fixture.Create<int>());
+
+            // Act
+            _sut.NotifyProgressChange(ProductScanStatus.ScannedNewLowest);
+
+            // Verify
+            Assert.True(_sut.HasNewLowestPrice);
+        }
+
+        [Fact]
+        public void ProductAutoScanStartedEvent_fired__Calls_NotifyStarted()
+        {
+            // Arrange
+            var count = 10;
+
+            // Act
+            _productAutoScanStartedEventSubject.OnNext(new ProductAutoScanStartedEvent(count));
+
+            // Verify
+            var expectedProgress = 1d / (count * 2);
+            Assert.True(_sut.IsStarted);
+            Assert.False(_sut.HasErrors);
+            Assert.False(_sut.HasNewLowestPrice);
+            Assert.Equal(0, _sut.FinishedJobs);
+            Assert.Equal(TrackerScanStatus.InProgress, _lastStatus);
+            Assert.Equal(expectedProgress, _lastProgress);
+        }
+    }
+}