Allow choosing a RAG folder or file by dropping it

app/MindWork AI Studio/Components/SelectDirectory.razor

@@ -1,19 +1,37 @@
 @inherits MSGComponentBase
 
-<MudStack Row="@true" Spacing="3" Class="mb-3" StretchItems="StretchItems.None" AlignItems="AlignItems.Center">
-    <MudTextField
-        T="string"
-        Text="@this.Directory"
-        Label="@this.Label"
-        ReadOnly="@true"
-        Validation="@this.Validation"
-        Adornment="Adornment.Start"
-        AdornmentIcon="@Icons.Material.Filled.Folder"
-        UserAttributes="@SPELLCHECK_ATTRIBUTES"
-        Variant="Variant.Outlined"
-    />
-    
-    <MudButton StartIcon="@Icons.Material.Filled.FolderOpen" Variant="Variant.Outlined" Color="Color.Primary" Disabled="@(this.Disabled || this.isDirectoryDialogOpen)" OnClick="@this.OpenDirectoryDialog">
-        @T("Choose Directory")
-    </MudButton>
-</MudStack>
+@if (this.EnableDragDrop)
+{
+    <PathDropZone Layer="@this.Layer" CatchAllDocuments="@this.CatchAllDocuments" Disabled="@this.Disabled" OnPathsDropped="@this.PathsDropped">
+        @this.Picker
+        <MudText Typo="Typo.body2">
+            @T("You can also drag & drop the folder here.")
+        </MudText>
+    </PathDropZone>
+}
+else
+{
+    @this.Picker
+}
+
+@code {
+
+    private RenderFragment Picker =>
+        @<MudStack Row="@true" Spacing="3" Class="mb-3" StretchItems="StretchItems.None" AlignItems="AlignItems.Center">
+            <MudTextField
+                T="string"
+                Text="@this.Directory"
+                Label="@this.Label"
+                ReadOnly="@true"
+                Validation="@this.Validation"
+                Adornment="Adornment.Start"
+                AdornmentIcon="@Icons.Material.Filled.Folder"
+                UserAttributes="@SPELLCHECK_ATTRIBUTES"
+                Variant="Variant.Outlined"
+            />
+
+            <MudButton StartIcon="@Icons.Material.Filled.FolderOpen" Variant="Variant.Outlined" Color="Color.Primary" Disabled="@(this.Disabled || this.isDirectoryDialogOpen)" OnClick="@this.OpenDirectoryDialog">
+                @T("Choose Directory")
+            </MudButton>
+        </MudStack>;
+}

app/MindWork AI Studio/Components/SelectDirectory.razor.cs

@@ -2,6 +2,9 @@ using AIStudio.Tools.Services;
 
 using Microsoft.AspNetCore.Components;
 
+// This component has a parameter called Directory, which would shadow the file system's Directory class:
+using IODirectory = System.IO.Directory;
+
 namespace AIStudio.Components;
 
 public partial class SelectDirectory : MSGComponentBase
@@ -24,6 +27,24 @@ public partial class SelectDirectory : MSGComponentBase
     [Parameter]
     public Func<string, string?> Validation { get; set; } = _ => null;
 
+    /// <summary>
+    /// When true, the folder can also be chosen by dropping it onto this component.
+    /// </summary>
+    [Parameter]
+    public bool EnableDragDrop { get; set; }
+
+    /// <summary>
+    /// On which layer to register the drop area. Higher layers have priority over lower layers.
+    /// </summary>
+    [Parameter]
+    public int Layer { get; set; } = DropLayers.ROOT;
+
+    /// <summary>
+    /// Catch all documents that are hovered over the AI Studio window and not only over the drop zone.
+    /// </summary>
+    [Parameter]
+    public bool CatchAllDocuments { get; set; }
+
     [Inject]
     public RustService RustService { get; set; } = null!;
     
@@ -69,4 +90,39 @@ public partial class SelectDirectory : MSGComponentBase
             this.isDirectoryDialogOpen = false;
         }
     }
+
+    /// <summary>
+    /// Takes the first dropped path which leads to a folder.
+    /// </summary>
+    /// <remarks>
+    /// A dropped file is rejected instead of being taken as its parent folder. Everything a folder
+    /// contains is processed, so guessing the parent of a mistakenly dropped file could pull in far
+    /// more data than the user meant to hand over.
+    /// </remarks>
+    /// <param name="paths">The dropped paths.</param>
+    private async Task PathsDropped(List<string> paths)
+    {
+        foreach (var path in paths)
+        {
+            if (!IODirectory.Exists(path))
+                continue;
+
+            this.Logger.LogInformation("The user dropped the directory '{DroppedDirectory}'.", path);
+            this.InternalDirectoryChanged(path);
+            return;
+        }
+
+        this.Logger.LogWarning("None of the {Count} dropped path(s) could be used as a directory.", paths.Count);
+        await this.MessageBus.SendWarning(new(Icons.Material.Filled.Warning, this.GetDropWarning(paths)));
+    }
+
+    private string GetDropWarning(List<string> paths)
+    {
+        // Naming the actual mistake beats a generic "that did not work". Dropping a file onto a
+        // folder picker is the likeliest of them:
+        if (paths.Any(File.Exists))
+            return T("Please drop a folder, not a file.");
+
+        return T("The dropped folder could not be accessed. Please choose it with the folder chooser instead.");
+    }
 }

app/MindWork AI Studio/Components/SelectFile.razor

@@ -1,19 +1,37 @@
 @inherits MSGComponentBase
 
-<MudStack Row="@true" Spacing="3" Class="mb-3" StretchItems="StretchItems.None" AlignItems="AlignItems.Center">
-    <MudTextField
-        T="string"
-        Text="@this.File"
-        Label="@this.Label"
-        ReadOnly="@true"
-        Validation="@this.Validation"
-        Adornment="Adornment.Start"
-        AdornmentIcon="@Icons.Material.Filled.AttachFile"
-        UserAttributes="@SPELLCHECK_ATTRIBUTES"
-        Variant="Variant.Outlined"
-    />
-    
-    <MudButton StartIcon="@Icons.Material.Filled.FolderOpen" Variant="Variant.Outlined" Color="Color.Primary" Disabled="@(this.Disabled || this.isFileDialogOpen)" OnClick="@this.OpenFileDialog">
-        @T("Choose File")
-    </MudButton>
-</MudStack>
+@if (this.EnableDragDrop)
+{
+    <PathDropZone Layer="@this.Layer" CatchAllDocuments="@this.CatchAllDocuments" Disabled="@this.Disabled" OnPathsDropped="@this.PathsDropped">
+        @this.Picker
+        <MudText Typo="Typo.body2">
+            @T("You can also drag & drop the file here.")
+        </MudText>
+    </PathDropZone>
+}
+else
+{
+    @this.Picker
+}
+
+@code {
+
+    private RenderFragment Picker =>
+        @<MudStack Row="@true" Spacing="3" Class="mb-3" StretchItems="StretchItems.None" AlignItems="AlignItems.Center">
+            <MudTextField
+                T="string"
+                Text="@this.File"
+                Label="@this.Label"
+                ReadOnly="@true"
+                Validation="@this.Validation"
+                Adornment="Adornment.Start"
+                AdornmentIcon="@Icons.Material.Filled.AttachFile"
+                UserAttributes="@SPELLCHECK_ATTRIBUTES"
+                Variant="Variant.Outlined"
+            />
+
+            <MudButton StartIcon="@Icons.Material.Filled.FolderOpen" Variant="Variant.Outlined" Color="Color.Primary" Disabled="@(this.Disabled || this.isFileDialogOpen)" OnClick="@this.OpenFileDialog">
+                @T("Choose File")
+            </MudButton>
+        </MudStack>;
+}

app/MindWork AI Studio/Components/SelectFile.razor.cs

@@ -3,6 +3,9 @@ using AIStudio.Tools.Services;
 
 using Microsoft.AspNetCore.Components;
 
+// This component has a parameter called File, which would shadow the file system's File class:
+using IOFile = System.IO.File;
+
 namespace AIStudio.Components;
 
 public partial class SelectFile : MSGComponentBase
@@ -28,6 +31,24 @@ public partial class SelectFile : MSGComponentBase
     [Parameter]
     public Func<string, string?> Validation { get; set; } = _ => null;
 
+    /// <summary>
+    /// When true, the file can also be chosen by dropping it onto this component.
+    /// </summary>
+    [Parameter]
+    public bool EnableDragDrop { get; set; }
+
+    /// <summary>
+    /// On which layer to register the drop area. Higher layers have priority over lower layers.
+    /// </summary>
+    [Parameter]
+    public int Layer { get; set; } = DropLayers.ROOT;
+
+    /// <summary>
+    /// Catch all documents that are hovered over the AI Studio window and not only over the drop zone.
+    /// </summary>
+    [Parameter]
+    public bool CatchAllDocuments { get; set; }
+
     [Inject]
     public RustService RustService { get; set; } = null!;
     
@@ -73,4 +94,46 @@ public partial class SelectFile : MSGComponentBase
             this.isFileDialogOpen = false;
         }
     }
+
+    /// <summary>
+    /// Takes the first dropped path which leads to a usable file.
+    /// </summary>
+    /// <remarks>
+    /// This component carries exactly one file, so a multi-selection cannot be honored as a whole.
+    /// A dropped folder is rejected instead of being read as "the first file inside it": the user
+    /// was asked for a file, and picking one for them would be a surprise.
+    /// </remarks>
+    /// <param name="paths">The dropped paths.</param>
+    private async Task PathsDropped(List<string> paths)
+    {
+        foreach (var path in paths)
+        {
+            if (!IOFile.Exists(path))
+                continue;
+
+            if (this.Filter is { Length: > 0 } && !FileTypes.IsAllowedPath(path, this.Filter))
+                continue;
+
+            this.Logger.LogInformation("The user dropped the file '{DroppedFilePath}'.", path);
+            this.InternalFileChanged(path);
+            return;
+        }
+
+        this.Logger.LogWarning("None of the {Count} dropped path(s) could be used as a file.", paths.Count);
+        await this.MessageBus.SendWarning(new(Icons.Material.Filled.Warning, this.GetDropWarning(paths)));
+    }
+
+    private string GetDropWarning(List<string> paths)
+    {
+        // Naming the actual mistake beats a generic "that did not work". Dropping a folder onto a
+        // file picker is the likeliest of them:
+        if (paths.Any(Directory.Exists))
+            return T("Please drop a file, not a folder.");
+
+        // The file exists, so the file type filter is what turned it down:
+        if (paths.Any(IOFile.Exists))
+            return T("Please drop a file with a supported file type.");
+
+        return T("The dropped file could not be accessed. Please choose it with the file chooser instead.");
+    }
 }