Fixed the file preview showing an empty document while the file was still being read (#907)

app/MindWork AI Studio/Dialogs/DocumentCheckDialog.razor

@@ -33,6 +33,16 @@
                 @T("The specified file could not be found. The file have been moved, deleted, renamed, or is otherwise inaccessible.")
             </MudAlert>
         }
+        else if (this.isLoadingContent)
+        {
+            <MudJustifiedText Typo="Typo.body1" Class="my-3">
+                @T("Please wait while we load the content of your file. Depending on the file type and size, this may take a moment.")
+            </MudJustifiedText>
+            <MudSkeleton Width="30%" Height="42px"/>
+            <MudSkeleton Width="80%"/>
+            <MudSkeleton Width="100%"/>
+            <MudSkeleton Width="90%"/>
+        }
         else if (this.loadFailureMessage is not null)
         {
             <MudAlert Severity="Severity.Error" Variant="Variant.Filled" Class="my-2">

app/MindWork AI Studio/Dialogs/DocumentCheckDialog.razor.cs

@@ -25,7 +25,13 @@ public partial class DocumentCheckDialog : MSGComponentBase
     /// Set when reading the file failed, so the dialog shows the reason instead of empty content.
     /// </summary>
     private string? loadFailureMessage;
-    
+
+    /// <summary>
+    /// True while we extract the file content. Reading happens after the first render, so the
+    /// dialog can tell the user that it is working instead of showing an empty document.
+    /// </summary>
+    private bool isLoadingContent;
+
     [Inject]
     private RustService RustService { get; init; } = null!;
     
@@ -35,24 +41,40 @@ public partial class DocumentCheckDialog : MSGComponentBase
     [Inject]
     private ILogger<DocumentCheckDialog> Logger { get; init; } = null!;
     
+    protected override async Task OnInitializedAsync()
+    {
+        //
+        // Decide before the first render whether we have to read the file at all. Images are shown
+        // as they are, a missing file shows its own message, and content a caller already handed
+        // us is reused instead of being extracted a second time:
+        //
+        this.isLoadingContent =
+            this.Document is not null &&
+            !this.Document.IsImage &&
+            this.Document.Exists &&
+            string.IsNullOrWhiteSpace(this.FileContent);
+
+        await base.OnInitializedAsync();
+    }
+
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
         if (firstRender && this.Document is not null)
         {
+            if (!this.isLoadingContent)
+                return;
+
             try
             {
-                if (!this.Document.IsImage)
-                {
-                    var extraction = await UserFile.LoadFileData(this.Document.FilePath, this.RustService, this.DialogService);
-                    this.FileContent = extraction.Content;
+                var extraction = await UserFile.LoadFileData(this.Document.FilePath, this.RustService, this.DialogService);
+                this.FileContent = extraction.Content;
 
-                    //
-                    // This dialog exists so the user can check what we hand to the AI. Showing an
-                    // empty document when reading the file failed would answer that question wrong.
-                    //
-                    if (!extraction.HasUsableContent)
-                        this.loadFailureMessage = extraction.ToUserMessage(this.Document.FileName);
-                }
+                //
+                // This dialog exists so the user can check what we hand to the AI. Showing an
+                // empty document when reading the file failed would answer that question wrong.
+                //
+                if (!extraction.HasUsableContent)
+                    this.loadFailureMessage = extraction.ToUserMessage(this.Document.FileName);
             }
             catch (Exception ex)
             {
@@ -60,8 +82,11 @@ public partial class DocumentCheckDialog : MSGComponentBase
                 this.FileContent = string.Empty;
                 this.loadFailureMessage = FileExtractionErrorCode.INTERNAL.ToUserMessage(this.Document.FileName);
             }
-            
-            this.StateHasChanged();
+            finally
+            {
+                this.isLoadingContent = false;
+                this.StateHasChanged();
+            }
         }
         else if (firstRender)
             this.Logger.LogWarning("Document check dialog opened without a valid file path.");