From 4725fe36d107fe07ff0486a4f78523c5dc9bfe4d Mon Sep 17 00:00:00 2001
From: Michael Bucari-Tovo <mbucari1@gmail.com>
Date: Fri, 6 Jan 2023 22:56:00 -0700
Subject: [PATCH] Add property changed filtering events to Configuration

---
 Source/FileLiberator/DownloadOptions.cs       |   9 +-
 .../Dialogs/SettingsDialog.axaml              |  48 ++-
 .../Dialogs/SettingsDialog.axaml.cs           |   9 +
 .../Views/MainWindow.ScanAuto.cs              |  10 +-
 .../Configuration.Logging.cs                  |   4 +-
 .../Configuration.PersistentSettings.cs       |   8 +-
 .../Configuration.PropertyChange.cs           | 153 +-------
 Source/LibationFileManager/Configuration.cs   |   6 +-
 .../PropertyChangeFilter.cs                   | 331 ++++++++++++++++++
 Source/LibationWinForms/Form1.ScanAuto.cs     |  13 +-
 10 files changed, 397 insertions(+), 194 deletions(-)
 create mode 100644 Source/LibationFileManager/PropertyChangeFilter.cs

diff --git a/Source/FileLiberator/DownloadOptions.cs b/Source/FileLiberator/DownloadOptions.cs
index 3b74aa2b..3ff022d2 100644
--- a/Source/FileLiberator/DownloadOptions.cs
+++ b/Source/FileLiberator/DownloadOptions.cs
@@ -81,11 +81,10 @@ namespace FileLiberator
 
 			LibraryBookDto = LibraryBook.ToDto();
 
-            cancellation =
-                Configuration.Instance
-                .SubscribeToPropertyChanged<long>(
-                    nameof(Configuration.DownloadSpeedLimit),
-                    (_, s) => DownloadSpeedChanged?.Invoke(this, s));
+          cancellation = Configuration.Instance
+                        .ObservePropertyChanged<long>(
+                            nameof(Configuration.DownloadSpeedLimit),
+                            (_, s) => DownloadSpeedChanged?.Invoke(this, s));
 		}
 	}
 }
diff --git a/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml b/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml
index b7c76037..ba5d1d62 100644
--- a/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml
+++ b/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml
@@ -2,7 +2,7 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="620"
+        mc:Ignorable="d" d:DesignWidth="850" d:DesignHeight="620"
 		MinWidth="800" MinHeight="620"
         x:Class="LibationAvalonia.Dialogs.SettingsDialog"
         xmlns:controls="clr-namespace:LibationAvalonia.Controls"
@@ -102,7 +102,7 @@
 								Click="OpenLogFolderButton_Click" />
 
 						</StackPanel>
-<!--
+						<!--
 						<CheckBox
 							Grid.Row="2"
 							Margin="5"
@@ -282,7 +282,7 @@
 									Grid.Column="0"
 									Margin="0,5,0,0"
 									Text="{Binding DownloadDecryptSettings.FolderTemplateText}" />
-								
+
 								<TextBox
 									Grid.Row="1"
 									Grid.Column="0"
@@ -356,21 +356,21 @@
 							Margin="5"
 							BorderWidth="1"
 							Label="Temporary Files Location">
-							
-						<StackPanel
-							Margin="5" >
 
-							<TextBlock
-								Margin="0,0,0,10"
-								Text="{Binding DownloadDecryptSettings.InProgressDescriptionText}" />
+							<StackPanel
+								Margin="5" >
 
-							<controls:DirectoryOrCustomSelectControl
-								SubDirectory="Libation"
-								Directory="{Binding DownloadDecryptSettings.InProgressDirectory, Mode=TwoWay}"
-								KnownDirectories="{Binding DownloadDecryptSettings.KnownDirectories}" />
+								<TextBlock
+									Margin="0,0,0,10"
+									Text="{Binding DownloadDecryptSettings.InProgressDescriptionText}" />
+
+								<controls:DirectoryOrCustomSelectControl
+									SubDirectory="Libation"
+									Directory="{Binding DownloadDecryptSettings.InProgressDirectory, Mode=TwoWay}"
+									KnownDirectories="{Binding DownloadDecryptSettings.KnownDirectories}" />
 
 
-						</StackPanel>
+							</StackPanel>
 						</controls:GroupBox>
 
 						<CheckBox
@@ -436,6 +436,26 @@
 
 							</CheckBox>
 
+							<StackPanel Orientation="Horizontal">
+								
+								<CheckBox
+									Margin="0,0,0,5"
+									IsChecked="{Binding AudioSettings.DownloadClipsBookmarks, Mode=TwoWay}">
+
+									<TextBlock
+										TextWrapping="Wrap"
+										Text="Download Clips, Notes and Bookmarks as" />
+
+								</CheckBox>
+								
+								<controls:WheelComboBox
+									Margin="5,0,0,0"
+									IsEnabled="{Binding AudioSettings.DownloadClipsBookmarks}"
+									Items="{Binding AudioSettings.ClipBookmarkFormats}"
+									SelectedItem="{Binding AudioSettings.ClipBookmarkFormat}"/>
+							
+							</StackPanel>
+
 							<CheckBox
 								Margin="0,0,0,5"
 								IsChecked="{Binding AudioSettings.RetainAaxFile, Mode=TwoWay}">
diff --git a/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml.cs b/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml.cs
index 8a134e40..0af59ebd 100644
--- a/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml.cs
+++ b/Source/LibationAvalonia/Dialogs/SettingsDialog.axaml.cs
@@ -10,6 +10,7 @@ using Dinah.Core;
 using System.Linq;
 using FileManager;
 using System.IO;
+using Avalonia.Collections;
 
 namespace LibationAvalonia.Dialogs
 {
@@ -381,6 +382,7 @@ namespace LibationAvalonia.Dialogs
 	public class AudioSettings : ViewModels.ViewModelBase, ISettingsDisplay
 	{
 
+		private bool _downloadClipsBookmarks;
 		private bool _splitFilesByChapter;
 		private bool _allowLibationFixup;
 		private bool _lameTargetBitrate;
@@ -401,6 +403,8 @@ namespace LibationAvalonia.Dialogs
 			AllowLibationFixup = config.AllowLibationFixup;
 			DownloadCoverArt = config.DownloadCoverArt;
 			RetainAaxFile = config.RetainAaxFile;
+			DownloadClipsBookmarks = config.DownloadClipsBookmarks;
+			ClipBookmarkFormat = config.ClipsBookmarksFileFormat;
 			SplitFilesByChapter = config.SplitFilesByChapter;
 			MergeOpeningAndEndCredits = config.MergeOpeningAndEndCredits;
 			StripAudibleBrandAudio = config.StripAudibleBrandAudio;
@@ -421,6 +425,8 @@ namespace LibationAvalonia.Dialogs
 			config.AllowLibationFixup = AllowLibationFixup;
 			config.DownloadCoverArt = DownloadCoverArt;
 			config.RetainAaxFile = RetainAaxFile;
+			config.DownloadClipsBookmarks = DownloadClipsBookmarks;
+			config.ClipsBookmarksFileFormat = ClipBookmarkFormat;
 			config.SplitFilesByChapter = SplitFilesByChapter;
 			config.MergeOpeningAndEndCredits = MergeOpeningAndEndCredits;
 			config.StripAudibleBrandAudio = StripAudibleBrandAudio;
@@ -437,6 +443,7 @@ namespace LibationAvalonia.Dialogs
 			return Task.FromResult(true);
 		}
 
+		public AvaloniaList<Configuration.ClipBookmarkFormat> ClipBookmarkFormats { get; } = new(Enum<Configuration.ClipBookmarkFormat>.GetValues());
 		public string CreateCueSheetText { get; } = Configuration.GetDescription(nameof(Configuration.CreateCueSheet));
 		public string AllowLibationFixupText { get; } = Configuration.GetDescription(nameof(Configuration.AllowLibationFixup));
 		public string DownloadCoverArtText { get; } = Configuration.GetDescription(nameof(Configuration.DownloadCoverArt));
@@ -450,6 +457,8 @@ namespace LibationAvalonia.Dialogs
 		public bool CreateCueSheet { get; set; }
 		public bool DownloadCoverArt { get; set; }
 		public bool RetainAaxFile { get; set; }
+		public bool DownloadClipsBookmarks { get => _downloadClipsBookmarks; set => this.RaiseAndSetIfChanged(ref _downloadClipsBookmarks, value); }
+		public Configuration.ClipBookmarkFormat ClipBookmarkFormat { get; set; }
 		public bool MergeOpeningAndEndCredits { get; set; }
 		public bool StripAudibleBrandAudio { get; set; }
 		public bool StripUnabridged { get; set; }
diff --git a/Source/LibationAvalonia/Views/MainWindow.ScanAuto.cs b/Source/LibationAvalonia/Views/MainWindow.ScanAuto.cs
index bdb0d2d1..cf3f5bba 100644
--- a/Source/LibationAvalonia/Views/MainWindow.ScanAuto.cs
+++ b/Source/LibationAvalonia/Views/MainWindow.ScanAuto.cs
@@ -55,11 +55,7 @@ namespace LibationAvalonia.Views
 			AccountsSettingsPersister.Saved += accountsPostSave;
 
 			// when autoscan setting is changed, update menu checkbox and run autoscan
-			Configuration.Instance.PropertyChanged += (_, e) =>
-			{
-				if (e.PropertyName == nameof(Configuration.Instance.AutoScan))
-					startAutoScan();
-			};
+			Configuration.Instance.PropertyChanged += startAutoScan;
 		}
 
 		private List<(string AccountId, string LocaleName)> preSaveDefaultAccounts;
@@ -83,9 +79,11 @@ namespace LibationAvalonia.Views
 				startAutoScan();
 		}
 
+		[PropertyChangeFilter(nameof(Configuration.AutoScan))]
 		private void startAutoScan(object sender = null, EventArgs e = null)
 		{
-			if (Configuration.Instance.AutoScan)
+			_viewModel.AutoScanChecked = Configuration.Instance.AutoScan;
+			if (_viewModel.AutoScanChecked)
 				autoScanTimer.PerformNow();
 			else
 				autoScanTimer.Stop();
diff --git a/Source/LibationFileManager/Configuration.Logging.cs b/Source/LibationFileManager/Configuration.Logging.cs
index 1c6ecee2..f5f9037d 100644
--- a/Source/LibationFileManager/Configuration.Logging.cs
+++ b/Source/LibationFileManager/Configuration.Logging.cs
@@ -36,7 +36,7 @@ namespace LibationFileManager
             }
             set
             {
-                PropertyChanging?.Invoke(this, new PropertyChangingEventArgsEx(nameof(LogLevel), LogLevel, value));
+				OnPropertyChanging(nameof(LogLevel), LogLevel, value);
                 var valueWasChanged = persistentDictionary.SetWithJsonPath("Serilog", "MinimumLevel", value.ToString());
                 if (!valueWasChanged)
                 {
@@ -46,7 +46,7 @@ namespace LibationFileManager
 
                 configuration.Reload();
 
-				PropertyChanged?.Invoke(this, new PropertyChangedEventArgsEx(nameof(LogLevel), value));
+				OnPropertyChanged(nameof(LogLevel), value);
 
 				Log.Logger.Information("Updated LogLevel MinimumLevel. {@DebugInfo}", new
                 {
diff --git a/Source/LibationFileManager/Configuration.PersistentSettings.cs b/Source/LibationFileManager/Configuration.PersistentSettings.cs
index 98458102..890617b1 100644
--- a/Source/LibationFileManager/Configuration.PersistentSettings.cs
+++ b/Source/LibationFileManager/Configuration.PersistentSettings.cs
@@ -28,9 +28,9 @@ namespace LibationFileManager
 			var existing = getExistingValue(propertyName);
 			if (existing?.Equals(newValue) is true) return;
 
-			PropertyChanging?.Invoke(this, new PropertyChangingEventArgsEx(propertyName, existing, newValue));
+			OnPropertyChanging(propertyName, existing, newValue);
 			persistentDictionary.SetNonString(propertyName, newValue);
-			PropertyChanged?.Invoke(this, new PropertyChangedEventArgsEx(propertyName, newValue));
+			OnPropertyChanged(propertyName, newValue);
 		}
 
 		public void SetString(string newValue, [CallerMemberName] string propertyName = "")
@@ -38,9 +38,9 @@ namespace LibationFileManager
 			var existing = getExistingValue(propertyName);
 			if (existing?.Equals(newValue) is true) return;
 
-			PropertyChanging?.Invoke(this, new PropertyChangingEventArgsEx(propertyName, existing, newValue));
+			OnPropertyChanging(propertyName, existing, newValue);
 			persistentDictionary.SetString(propertyName, newValue);
-			PropertyChanged?.Invoke(this, new PropertyChangedEventArgsEx(propertyName, newValue));
+			OnPropertyChanged(propertyName, newValue);
 		}
 
 		private object getExistingValue(string propertyName)
diff --git a/Source/LibationFileManager/Configuration.PropertyChange.cs b/Source/LibationFileManager/Configuration.PropertyChange.cs
index e923b12d..ff47f0c9 100644
--- a/Source/LibationFileManager/Configuration.PropertyChange.cs
+++ b/Source/LibationFileManager/Configuration.PropertyChange.cs
@@ -1,158 +1,9 @@
-using Dinah.Core;
-using Newtonsoft.Json.Linq;
-using System;
-using System.Collections.Generic;
-using System.ComponentModel;
+using System.Collections.Generic;
 
 namespace LibationFileManager
 {
-	public partial class Configuration : INotifyPropertyChanging, INotifyPropertyChanged
+	public partial class Configuration : PropertyChangeFilter
 	{
-		public event PropertyChangingEventHandler PropertyChanging;
-		public event PropertyChangedEventHandler PropertyChanged;
-		private readonly Dictionary<string, List<MulticastDelegate>> propertyChangedActions = new();
-		private readonly Dictionary<string, List<MulticastDelegate>> propertyChangingActions = new();
-
-		/// <summary>
-		/// Clear all subscriptions to Property<b>Changed</b> for <paramref name="propertyName"/>
-		/// </summary>
-		public void ClearChangedSubscriptions(string propertyName)
-		{
-			if (propertyChangedActions.ContainsKey(propertyName)
-				&& propertyChangedActions[propertyName] is not null)
-				propertyChangedActions[propertyName].Clear();
-		}
-
-		/// <summary>
-		/// Clear all subscriptions to Property<b>Changing</b> for <paramref name="propertyName"/>
-		/// </summary>
-		public void ClearChangingSubscriptions(string propertyName)
-		{
-			if (propertyChangingActions.ContainsKey(propertyName)
-				&& propertyChangingActions[propertyName] is not null)
-				propertyChangingActions[propertyName].Clear();
-		}
-
-		/// <summary>
-		/// Add an action to be executed when a property's value has changed
-		/// </summary>
-		/// <typeparam name="T">The <paramref name="propertyName"/>'s <see cref="Type"/></typeparam>
-		/// <param name="propertyName">Name of the property whose change triggers the <paramref name="action"/></param>
-		/// <param name="action">Action to be executed with parameters: <paramref name="propertyName"/> and <strong>NewValue</strong></param>
-		/// <returns>A reference to an interface that allows observers to stop receiving notifications before the provider has finished sending them.</returns>
-		public IDisposable SubscribeToPropertyChanged<T>(string propertyName, Action<string, T> action)
-		{
-			validateSubscriber<T>(propertyName, action);
-
-			if (!propertyChangedActions.ContainsKey(propertyName))
-				propertyChangedActions.Add(propertyName, new List<MulticastDelegate>());
-
-			var actionlist = propertyChangedActions[propertyName];
-
-			if (!actionlist.Contains(action))
-				actionlist.Add(action);
-
-			return new Unsubscriber(actionlist, action);
-		}
-
-		/// <summary>
-		/// Add an action to be executed when a property's value is changing
-		/// </summary>
-		/// <typeparam name="T">The <paramref name="propertyName"/>'s <see cref="Type"/></typeparam>
-		/// <param name="propertyName">Name of the property whose change triggers the <paramref name="action"/></param>
-		/// <param name="action">Action to be executed with parameters: <paramref name="propertyName"/>, <b>OldValue</b>, and <b>NewValue</b></param>
-		/// <returns>A reference to an interface that allows observers to stop receiving notifications before the provider has finished sending them.</returns>
-		public IDisposable SubscribeToPropertyChanging<T>(string propertyName, Action<string, T, T> action)
-		{
-			validateSubscriber<T>(propertyName, action);
-
-			if (!propertyChangingActions.ContainsKey(propertyName))
-				propertyChangingActions.Add(propertyName, new List<MulticastDelegate>());
-
-			var actionlist = propertyChangingActions[propertyName];
-
-			if (!actionlist.Contains(action))
-				actionlist.Add(action);
-
-			return new Unsubscriber(actionlist, action);
-		}
-
-		private void validateSubscriber<T>(string propertyName, MulticastDelegate action)
-		{
-			ArgumentValidator.EnsureNotNullOrWhiteSpace(propertyName, nameof(propertyName));
-			ArgumentValidator.EnsureNotNull(action, nameof(action));
-
-			var propertyInfo = GetType().GetProperty(propertyName);
-
-			if (propertyInfo is null)
-				throw new MissingMemberException($"{nameof(Configuration)}.{propertyName} does not exist.");
-
-			if (propertyInfo.PropertyType != typeof(T))
-				throw new InvalidCastException($"{nameof(Configuration)}.{propertyName} is {propertyInfo.PropertyType}, but parameter is {typeof(T)}.");
-		}
-
-		private void Configuration_PropertyChanged(object sender, PropertyChangedEventArgs e)
-		{
-			if (e is PropertyChangedEventArgsEx args && propertyChangedActions.ContainsKey(args.PropertyName))
-			{
-				foreach (var action in propertyChangedActions[args.PropertyName])
-				{
-					action.DynamicInvoke(args.PropertyName, args.NewValue);
-				}
-			}
-		}
-
-		private void Configuration_PropertyChanging(object sender, PropertyChangingEventArgs e)
-		{
-			if (e is PropertyChangingEventArgsEx args && propertyChangingActions.ContainsKey(args.PropertyName))
-			{
-				foreach (var action in propertyChangingActions[args.PropertyName])
-				{
-					action.DynamicInvoke(args.PropertyName, args.OldValue, args.NewValue);
-				}
-			}
-		}
-
-		private class PropertyChangingEventArgsEx : PropertyChangingEventArgs
-		{
-			public object OldValue { get; }
-			public object NewValue { get; }
-
-			public PropertyChangingEventArgsEx(string propertyName, object oldValue, object newValue) : base(propertyName)
-			{
-				OldValue = oldValue;
-				NewValue = newValue;
-			}
-		}
-
-		private class PropertyChangedEventArgsEx : PropertyChangedEventArgs
-		{
-			public object NewValue { get; }
-
-			public PropertyChangedEventArgsEx(string propertyName, object newValue) : base(propertyName)
-			{
-				NewValue = newValue;
-			}
-		}
-
-		private class Unsubscriber : IDisposable
-		{
-			private List<MulticastDelegate> _observers;
-			private MulticastDelegate _observer;
-
-			internal Unsubscriber(List<MulticastDelegate> observers, MulticastDelegate observer)
-			{
-				_observers = observers;
-				_observer = observer;
-			}
-
-			public void Dispose()
-			{
-				if (_observers.Contains(_observer))
-					_observers.Remove(_observer);
-			}
-		}
-
 		/*
 		 * Use this type in the getter for any Dictionary<TKey, TValue> settings,
 		 * and be sure to clone it before returning. This allows Configuration to
diff --git a/Source/LibationFileManager/Configuration.cs b/Source/LibationFileManager/Configuration.cs
index 517bce8d..d40ba59a 100644
--- a/Source/LibationFileManager/Configuration.cs
+++ b/Source/LibationFileManager/Configuration.cs
@@ -32,11 +32,7 @@ namespace LibationFileManager
 
 		#region singleton stuff
 		public static Configuration Instance { get; } = new Configuration();
-		private Configuration()
-		{
-			PropertyChanging += Configuration_PropertyChanging;
-			PropertyChanged += Configuration_PropertyChanged;
-		}
+		private Configuration() { }
 		#endregion
 	}
 }
diff --git a/Source/LibationFileManager/PropertyChangeFilter.cs b/Source/LibationFileManager/PropertyChangeFilter.cs
new file mode 100644
index 00000000..9bbbbe2b
--- /dev/null
+++ b/Source/LibationFileManager/PropertyChangeFilter.cs
@@ -0,0 +1,331 @@
+using Dinah.Core;
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+
+namespace LibationFileManager
+{
+	#region Useage
+
+	/*
+	 * USEAGE
+	 
+		*************************
+		*						*
+		*   Event Filter Mode   *
+		*						*
+		*************************
+
+	 
+	 	propertyChangeFilter.PropertyChanged += MyPropertiesChanged;
+
+		[PropertyChangeFilter("MyProperty1")]
+		[PropertyChangeFilter("MyProperty2")]
+		void MyPropertiesChanged(object sender, PropertyChangedEventArgsEx e)
+		{
+			// Only properties whose names match either "MyProperty1"
+			// or "MyProperty2" will fire this event handler.
+		}
+
+	******
+	* OR *
+	******
+	
+		propertyChangeFilter.PropertyChanged +=
+			[PropertyChangeFilter("MyProperty1")]
+			[PropertyChangeFilter("MyProperty2")]
+			(_, _) => 
+			{
+				// Only properties whose names match either "MyProperty1"
+				// or "MyProperty2" will fire this event handler.
+			};
+
+
+		*************************
+		*						*
+		*    Observable Mode	*
+		*						*
+		*************************
+		
+		using var cancellation = propertyChangeFilter.ObservePropertyChanging<int>("MyProperty", MyPropertyChanging);
+		
+        void MyPropertyChanging(string propertyName, int oldValue, int newValue)
+        {
+			// Only the property whose name match
+			// "MyProperty" will fire this method.
+        }
+	
+		//The observer is delisted when cancellation is disposed
+
+	******
+	* OR *
+	******
+	
+		using var cancellation = propertyChangeFilter.ObservePropertyChanged<bool>("MyProperty", (_, s) =>
+			{
+				// Only the property whose name match
+				// "MyProperty" will fire this action.
+			});
+		
+		//The observer is delisted when cancellation is disposed
+
+	 */
+
+	#endregion
+
+	public abstract class PropertyChangeFilter
+	{
+		private readonly Dictionary<string, List<Delegate>> propertyChangedActions = new();
+		private readonly Dictionary<string, List<Delegate>> propertyChangingActions = new();
+		
+		private readonly List<KeyValuePair<PropertyChangedEventHandlerEx, PropertyChangedEventHandlerEx>> changedFilters = new();
+		private readonly List<KeyValuePair<PropertyChangingEventHandlerEx, PropertyChangingEventHandlerEx>> changingFilters = new();
+
+		public PropertyChangeFilter()
+		{
+			PropertyChanging += Configuration_PropertyChanging;
+			PropertyChanged += Configuration_PropertyChanged;
+		}
+
+		#region Events
+
+		protected void OnPropertyChanged(string propertyName, object newValue)
+			=> _propertyChanged?.Invoke(this, new(propertyName, newValue));
+		protected void OnPropertyChanging(string propertyName, object oldValue, object newValue)
+			=> _propertyChanging?.Invoke(this, new(propertyName, oldValue, newValue));
+
+		private PropertyChangedEventHandlerEx _propertyChanged;
+		private PropertyChangingEventHandlerEx _propertyChanging;
+
+		public event PropertyChangedEventHandlerEx PropertyChanged
+		{
+			add
+			{
+				var attributes = Attribute.GetCustomAttributes(value.Method, typeof(PropertyChangeFilterAttribute)) as PropertyChangeFilterAttribute[];
+
+				if (attributes.Any())
+				{
+					var matches = attributes.Select(a => a.PropertyName).ToArray();
+
+					void filterer(object s, PropertyChangedEventArgsEx e)
+					{
+						if (e.PropertyName.In(matches)) value(s, e);
+					}
+
+					changedFilters.Add(new(value, filterer));
+
+					_propertyChanged += filterer;
+				}
+				else
+					_propertyChanged += value;
+			}
+			remove
+			{
+				var del = changedFilters.LastOrDefault(d => d.Key == value);
+				if (del.Key is null)
+					_propertyChanged -= value;
+				else
+				{
+					_propertyChanged -= del.Value;
+					changedFilters.Remove(del);
+				}
+			}
+		}
+
+		public event PropertyChangingEventHandlerEx PropertyChanging
+		{
+			add
+			{
+				var attributes = Attribute.GetCustomAttributes(value.Method, typeof(PropertyChangeFilterAttribute)) as PropertyChangeFilterAttribute[];
+
+				if (attributes.Any())
+				{
+					var matches = attributes.Select(a => a.PropertyName).ToArray();
+
+					void filterer(object s, PropertyChangingEventArgsEx e)
+					{
+						if (e.PropertyName.In(matches)) value(s, e);
+					}
+
+					changingFilters.Add(new(value, filterer));
+
+					_propertyChanging += filterer;
+
+				}
+				else
+					_propertyChanging += value;
+			}
+			remove
+			{
+				var del = changingFilters.LastOrDefault(d => d.Key == value);
+				if (del.Key is null)
+					_propertyChanging -= value;
+				else
+				{
+					_propertyChanging -= del.Value;
+					changingFilters.Remove(del);
+				}
+			}
+		}
+
+		#endregion
+
+		#region Observables
+
+		/// <summary>
+		/// Clear all subscriptions to Property<b>Changed</b> for <paramref name="propertyName"/>
+		/// </summary>
+		public void ClearChangedSubscriptions(string propertyName)
+		{
+			if (propertyChangedActions.ContainsKey(propertyName)
+				&& propertyChangedActions[propertyName] is not null)
+				propertyChangedActions[propertyName].Clear();
+		}
+
+		/// <summary>
+		/// Clear all subscriptions to Property<b>Changing</b> for <paramref name="propertyName"/>
+		/// </summary>
+		public void ClearChangingSubscriptions(string propertyName)
+		{
+			if (propertyChangingActions.ContainsKey(propertyName)
+				&& propertyChangingActions[propertyName] is not null)
+				propertyChangingActions[propertyName].Clear();
+		}
+
+		/// <summary>
+		/// Add an action to be executed when a property's value has changed
+		/// </summary>
+		/// <typeparam name="T">The <paramref name="propertyName"/>'s <see cref="Type"/></typeparam>
+		/// <param name="propertyName">Name of the property whose change triggers the <paramref name="action"/></param>
+		/// <param name="action">Action to be executed with parameters: <paramref name="propertyName"/> and <strong>NewValue</strong></param>
+		/// <returns>A reference to an interface that allows observers to stop receiving notifications before the provider has finished sending them.</returns>
+		public IDisposable ObservePropertyChanged<T>(string propertyName, Action<string, T> action)
+		{
+			validateSubscriber<T>(propertyName, action);
+
+			if (!propertyChangedActions.ContainsKey(propertyName))
+				propertyChangedActions.Add(propertyName, new List<Delegate>());
+
+			var actionlist = propertyChangedActions[propertyName];
+
+			if (!actionlist.Contains(action))
+				actionlist.Add(action);
+
+			return new Unsubscriber(actionlist, action);
+		}
+
+		/// <summary>
+		/// Add an action to be executed when a property's value is changing
+		/// </summary>
+		/// <typeparam name="T">The <paramref name="propertyName"/>'s <see cref="Type"/></typeparam>
+		/// <param name="propertyName">Name of the property whose change triggers the <paramref name="action"/></param>
+		/// <param name="action">Action to be executed with parameters: <paramref name="propertyName"/>, <b>OldValue</b>, and <b>NewValue</b></param>
+		/// <returns>A reference to an interface that allows observers to stop receiving notifications before the provider has finished sending them.</returns>
+		public IDisposable ObservePropertyChanging<T>(string propertyName, Action<string, T, T> action)
+		{
+			validateSubscriber<T>(propertyName, action);
+
+			if (!propertyChangingActions.ContainsKey(propertyName))
+				propertyChangingActions.Add(propertyName, new List<Delegate>());
+
+			var actionlist = propertyChangingActions[propertyName];
+
+			if (!actionlist.Contains(action))
+				actionlist.Add(action);
+
+			return new Unsubscriber(actionlist, action);
+		}
+
+		private void validateSubscriber<T>(string propertyName, Delegate action)
+		{
+			ArgumentValidator.EnsureNotNullOrWhiteSpace(propertyName, nameof(propertyName));
+			ArgumentValidator.EnsureNotNull(action, nameof(action));
+
+			var propertyInfo = GetType().GetProperty(propertyName);
+
+			if (propertyInfo is null)
+				throw new MissingMemberException($"{nameof(Configuration)}.{propertyName} does not exist.");
+
+			if (propertyInfo.PropertyType != typeof(T))
+				throw new InvalidCastException($"{nameof(Configuration)}.{propertyName} is {propertyInfo.PropertyType}, but parameter is {typeof(T)}.");
+		}
+
+		private void Configuration_PropertyChanged(object sender, PropertyChangedEventArgsEx e)
+		{
+			if (propertyChangedActions.ContainsKey(e.PropertyName))
+			{
+				foreach (var action in propertyChangedActions[e.PropertyName])
+				{
+					action.DynamicInvoke(e.PropertyName, e.NewValue);
+				}
+			}
+		}
+
+		private void Configuration_PropertyChanging(object sender, PropertyChangingEventArgsEx e)
+		{
+			if (propertyChangingActions.ContainsKey(e.PropertyName))
+			{
+				foreach (var action in propertyChangingActions[e.PropertyName])
+				{
+					action.DynamicInvoke(e.PropertyName, e.OldValue, e.NewValue);
+				}
+			}
+		}
+
+		private class Unsubscriber : IDisposable
+		{
+			private List<Delegate> _observers;
+			private Delegate _observer;
+
+			internal Unsubscriber(List<Delegate> observers, Delegate observer)
+			{
+				_observers = observers;
+				_observer = observer;
+			}
+
+			public void Dispose()
+			{
+				if (_observers.Contains(_observer))
+					_observers.Remove(_observer);
+			}
+		}
+
+		#endregion
+	}
+
+	public delegate void PropertyChangedEventHandlerEx(object sender, PropertyChangedEventArgsEx e);
+	public delegate void PropertyChangingEventHandlerEx(object sender, PropertyChangingEventArgsEx e);
+
+	public class PropertyChangedEventArgsEx : PropertyChangedEventArgs
+	{
+		public object NewValue { get; }
+
+		public PropertyChangedEventArgsEx(string propertyName, object newValue) : base(propertyName)
+		{
+			NewValue = newValue;
+		}
+	}
+
+	public class PropertyChangingEventArgsEx : PropertyChangingEventArgs
+	{
+		public object OldValue { get; }
+		public object NewValue { get; }
+
+		public PropertyChangingEventArgsEx(string propertyName, object oldValue, object newValue) : base(propertyName)
+		{
+			OldValue = oldValue;
+			NewValue = newValue;
+		}
+	}
+
+	[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+	public class PropertyChangeFilterAttribute : Attribute
+	{
+		public string PropertyName { get; }
+		public PropertyChangeFilterAttribute(string propertyName)
+		{
+			PropertyName = propertyName;
+		}
+	}
+}
diff --git a/Source/LibationWinForms/Form1.ScanAuto.cs b/Source/LibationWinForms/Form1.ScanAuto.cs
index 11dd1407..916d49b6 100644
--- a/Source/LibationWinForms/Form1.ScanAuto.cs
+++ b/Source/LibationWinForms/Form1.ScanAuto.cs
@@ -59,14 +59,13 @@ namespace LibationWinForms
 			Configuration.Instance.PropertyChanged += Configuration_PropertyChanged;
 		}
 
-		private void Configuration_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
+
+		[PropertyChangeFilter(nameof(Configuration.AutoScan))]
+		private void Configuration_PropertyChanged(object sender, PropertyChangedEventArgsEx e)
 		{
-			if (e.PropertyName == nameof(Configuration.Instance.AutoScan))
-			{
-				// when autoscan setting is changed, update menu checkbox and run autoscan
-				updateAutoScanLibraryToolStripMenuItem(sender, e);
-				startAutoScan(sender, e);
-			}
+			// when autoscan setting is changed, update menu checkbox and run autoscan
+			updateAutoScanLibraryToolStripMenuItem(sender, e);
+			startAutoScan(sender, e);
 		}
 
 		private List<(string AccountId, string LocaleName)> preSaveDefaultAccounts;