Basic echo implementation

Decho/Views/MessageComposerView.axaml.cs

@@ -1,4 +1,9 @@
+using System.Linq;
 using Avalonia.Controls;
+using Avalonia.Input;
+using Avalonia.Interactivity;
+using Avalonia.Platform.Storage;
+using Decho.ViewModels;
 
 namespace Decho.Views;
 
@@ -7,5 +12,50 @@ public partial class MessageComposerView : UserControl
     public MessageComposerView()
     {
         InitializeComponent();
+        AddHandler(DragDrop.DragOverEvent, OnDragOver);
+        AddHandler(DragDrop.DropEvent, OnDrop);
+        DragDrop.SetAllowDrop(this, true);
+    }
+
+    private async void OnFileUploadClicked(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not MessageComposerViewModel vm) return;
+
+        var topLevel = TopLevel.GetTopLevel(this);
+        if (topLevel?.StorageProvider is null) return;
+
+        var files = await topLevel.StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
+        {
+            AllowMultiple = false,
+            Title = "Select a file to upload",
+        });
+
+        var file = files?.FirstOrDefault();
+        if (file?.TryGetLocalPath() is string path)
+        {
+            vm.RequestFileUpload(path);
+        }
+    }
+
+    private void OnDragOver(object? sender, DragEventArgs e)
+    {
+#pragma warning disable CS0618
+        if (e.Data.Contains(DataFormats.Files))
+#pragma warning restore CS0618
+            e.DragEffects = DragDropEffects.Copy;
+    }
+
+    private void OnDrop(object? sender, DragEventArgs e)
+    {
+        if (DataContext is not MessageComposerViewModel vm) return;
+
+#pragma warning disable CS0618
+        var paths = e.Data.GetFiles()?
+            .Select(f => f.TryGetLocalPath())
+            .FirstOrDefault(p => p is not null);
+#pragma warning restore CS0618
+
+        if (paths is string path)
+            vm.RequestFileUpload(path);
     }
 }