first pass at implementing the UI. Not sure that everything actually works yet, still needs more testing.

Gen3Hex/View/WindowsFileSystem.cs

@@ -0,0 +1,42 @@
+using HavenSoft.Gen3Hex.Model;
+using Microsoft.Win32;
+using System.IO;
+using System.Linq;
+using System.Windows;
+
+namespace HavenSoft.Gen3Hex.View {
+   public class WindowsFileSystem : IFileSystem {
+      public LoadedFile OpenFile(params string[] extensionOptions) {
+         var dialog = new OpenFileDialog { Filter = CreateFilterFromOptions(extensionOptions) };
+         var result = dialog.ShowDialog();
+         if (result != true) return null;
+         if (!File.Exists(dialog.FileName)) return null;
+         var data = File.ReadAllBytes(dialog.FileName);
+         return new LoadedFile(dialog.FileName, data);
+      }
+
+      public string RequestNewName(string currentName, params string[] extensionOptions) {
+         var dialog = new SaveFileDialog { FileName = currentName, Filter = CreateFilterFromOptions(extensionOptions) };
+         var result = dialog.ShowDialog();
+         if (result != true) return null;
+         return dialog.FileName;
+      }
+
+      public bool Save(LoadedFile file) {
+         if (!File.Exists(file.Name)) return false;
+         File.WriteAllBytes(file.Name, file.Contents);
+         return true;
+      }
+
+      public bool? TrySavePrompt(LoadedFile file) {
+         var result = MessageBox.Show($"Would you like to save {file.Name}?", Application.Current.MainWindow.Title, MessageBoxButton.YesNoCancel);
+         if (result == MessageBoxResult.Cancel) return null;
+         if (result == MessageBoxResult.No) return false;
+         return Save(file);
+      }
+
+      private static string CreateFilterFromOptions(string[] extensionOptions) {
+         return string.Join(",", extensionOptions.Select(option => $"*.{option}"));
+      }
+   }
+}