Added internal Operation Infrastructure + Example

- Overwrite might be a bad example, because it has no fail conditions. The intended behaviour for those is to throw an exception for invalid parameters, with an error text describing to the user what went wrong.
- Fail condition check may be moved to a seperate abstract method, forcing implementers to at least give fail conditions a thought.
- Minor refactor
- TODO: Better folder structure to group operations (Looking for suggestions)

BFR/MainWindow.xaml.cs

@@ -17,9 +17,7 @@ namespace BFR
 {
     public partial class MainWindow : Window
     {
-        public async Task OpenDirectoryButtonClick() =>
+        public async Task OpenDirectoryButtonClick() => OpenDirectory(await new OpenFolderDialog() { Directory = WorkingDirectory }.ShowAsync(this));
-            OpenDirectory(await new OpenFolderDialog() { Directory = WorkingDirectory }.ShowAsync(this));
-
         public void OpenDirectory(string directory)
         {
             WorkingDirectory = directory;
@@ -51,9 +49,7 @@ namespace BFR
             Files.ReplaceAll(new List<FileModel>(Files));
         }
 
-        public MainWindow() => 
+        public MainWindow() => InitializeComponent();
-            InitializeComponent();
-
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);

BFR/Operations/Operation.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+
+using Avalonia;
+
+using BFR.DataModels;
+
+namespace BFR.Operations
+{
+    public abstract class Operation : AvaloniaObject
+    {
+        // Needs to be an avalonia property to update the UI with with any potential error.
+        public AvaloniaProperty<string> errorProperty = AvaloniaProperty.Register<Operation, string>(nameof(Error), defaultValue: "");
+        public string Error { get => GetValue(errorProperty); set => SetValue(errorProperty, value); }
+        public bool IsEnabled { get; set; } = true;
+        public abstract string Name { get; }
+        public abstract string Description { get; }
+        public abstract OperationType OperationType { get; }
+
+        protected abstract void ApplyToInternal(List<FileModel> files);
+        
+        // Updates the UI with the appropriate error if the operation fails
+        public void ApplyTo(List<FileModel> files)
+        {
+            try { ApplyToInternal(files); Error = ""; }
+            catch (Exception e) { Error = e.Message; }
+        }
+    }
+}

BFR/Operations/OperationType.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace BFR.Operations
+{
+    public class OperationType
+    {
+        public string Name { get; }
+        public string Description { get; }
+        public Func<Operation> Create { get; }
+
+        internal static OperationType Make<T>() where T : Operation, new()
+        {
+            var pilot = new T();
+            return new OperationType(pilot.Name, pilot.Description, () => new T());
+        }
+
+        private OperationType(string name, string description, Func<Operation> create) =>
+            (Name, Description, Create) = (name, description, create);
+    }
+}

BFR/Operations/Overwrite.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+
+using BFR.DataModels;
+
+namespace BFR.Operations
+{
+    public class Overwrite : Operation
+    {
+        // Operation Info
+        public override string Name => nameof(Overwrite);
+        public override string Description => "Overwrites all file names. To produce a valid result this has to be combined with numbering.";
+        public override OperationType OperationType { get; } = OperationType.Make<Overwrite>();
+
+        // Operation Parameters
+        public string Replacement { get; set; } = "";
+        public bool FullName { get; set; } = false;
+
+        protected override void ApplyToInternal(List<FileModel> files)
+        {
+            // Fail conditions: No fail conditions
+            // Apply Operation
+            foreach (var file in files)
+                if (FullName) file.FullName = Replacement;
+                else file.Name = Replacement;
+        }
+    }
+}