Changed the ERI Server assistant to save its specification through a save dialog

app/MindWork AI Studio/Assistants/ERI/AssistantERI.razor

@@ -116,8 +116,8 @@ else
             </MudSelectItem>
         }
     </MudSelect>
-    <MudButton Variant="Variant.Outlined" Size="Size.Small" Disabled="@this.IsSpecificationDownloadDisabled" Href="@this.selectedERIVersion.SpecificationURL()" Target="_blank">
-        <MudIcon Icon="@Icons.Material.Filled.Link" Class="mr-2"/> @T("Download specification")
+    <MudButton Variant="Variant.Outlined" Size="Size.Small" Disabled="@this.IsSpecificationSavingDisabled" OnClick="@this.SaveSpecificationAsync">
+        <MudIcon Icon="@Icons.Material.Filled.Save" Class="mr-2"/> @T("Save specification")
     </MudButton>
 </MudStack>
 

app/MindWork AI Studio/Assistants/ERI/AssistantERI.razor.cs

@@ -3,6 +3,7 @@ using AIStudio.Dialogs;
 using AIStudio.Dialogs.Settings;
 using AIStudio.Settings.DataModel;
 using AIStudio.Tools.AssistantSessions;
+using AIStudio.Tools.Rust;
 
 using Microsoft.AspNetCore.Components;
 
@@ -375,9 +376,43 @@ public partial class AssistantERI : AssistantBaseCore<SettingsDialogERIServer>
     private bool IsERIInputDisabled => this.IsNoneERIServerSelected || this.IsProcessing;
 
     /// <summary>
-    /// Gets whether the selected ERI specification cannot be downloaded.
+    /// Gets whether the selected ERI specification cannot be saved.
     /// </summary>
-    private bool IsSpecificationDownloadDisabled => !this.selectedERIVersion.WasSpecificationSelected() || this.IsERIInputDisabled;
+    private bool IsSpecificationSavingDisabled => !this.selectedERIVersion.WasSpecificationSelected() || this.IsERIInputDisabled;
+
+    /// <summary>
+    /// Lets the user save the selected ERI specification, a copy of the one the app carries.
+    /// </summary>
+    /// <remarks>
+    /// The app server answers the app window only, so a link to the file would fail in the browser
+    /// of the system. The copy also matches the installed version of AI Studio.
+    /// </remarks>
+    private async Task SaveSpecificationAsync()
+    {
+        var specificationPath = this.selectedERIVersion.SpecificationURL();
+        var response = await this.RustService.SaveFile(T("Save the ERI specification"), [FileTypes.JSON], Path.GetFileName(specificationPath));
+        if (response.UserCancelled)
+            return;
+
+        await using var feedback = new FileExportFeedback();
+        feedback.ShowRunning(response.SaveFilePath);
+        try
+        {
+            if (await this.WebRootFiles.CopyToAsync(specificationPath, response.SaveFilePath))
+            {
+                await feedback.SucceededAsync(Icons.Material.Filled.CheckCircle, T("The ERI specification was saved."), response.SaveFilePath, true);
+                return;
+            }
+
+            this.Logger.LogError("The app carries no ERI specification at '{SpecificationPath}'.", specificationPath);
+        }
+        catch (Exception exception)
+        {
+            this.Logger.LogError(exception, "Failed to save the ERI specification {ERIVersion}.", this.selectedERIVersion);
+        }
+
+        await MessageBus.INSTANCE.SendError(new(Icons.Material.Filled.Cancel, T("The ERI specification could not be saved.")));
+    }
 
     /// <summary>
     /// Gets whether the generated-code target directory selection should be disabled.

app/MindWork AI Studio/Tools/WebRootFiles.cs

@@ -34,4 +34,22 @@ public sealed class WebRootFiles
         using var reader = new StreamReader(fileStream);
         return await reader.ReadToEndAsync();
     }
+
+    /// <summary>
+    /// Copies a file below wwwroot to the given place, such as one the user chose to save it to.
+    /// </summary>
+    /// <param name="path">The path below wwwroot, such as <c>specs/eri/v1.json</c>.</param>
+    /// <param name="destinationPath">Where to write the copy. An existing file there gets replaced.</param>
+    /// <returns>True when the copy was written, false when there is no such file below wwwroot.</returns>
+    public async Task<bool> CopyToAsync(string path, string destinationPath)
+    {
+        var file = this.FileProvider.GetFileInfo(path);
+        if (!file.Exists)
+            return false;
+
+        await using var source = file.CreateReadStream();
+        await using var destination = File.Create(destinationPath);
+        await source.CopyToAsync(destination);
+        return true;
+    }
 }

app/Tests/Tools/AppAccess/WebRootFilesTests.cs

@@ -40,4 +40,34 @@ public sealed class WebRootFilesTests
         var text = await new WebRootFiles().ReadTextAsync("changelog/does-not-exist.md");
         Assert.That(text, Is.Empty);
     }
+
+    [TestCaseSource(nameof(SpecificationVersions))]
+    public async Task EveryERISpecificationCanBeSaved(ERIVersion version)
+    {
+        var webRootFiles = new WebRootFiles();
+        var destinationPath = Path.Combine(Path.GetTempPath(), $"eri-specification-{Guid.NewGuid():N}.json");
+        try
+        {
+            Assert.That(await webRootFiles.CopyToAsync(version.SpecificationURL(), destinationPath), Is.True);
+            Assert.That(await File.ReadAllTextAsync(destinationPath), Is.EqualTo(await version.ReadSpecification(webRootFiles)));
+        }
+        finally
+        {
+            File.Delete(destinationPath);
+        }
+    }
+
+    [Test]
+    public async Task AMissingFileIsNotCopied()
+    {
+        var destinationPath = Path.Combine(Path.GetTempPath(), $"eri-specification-{Guid.NewGuid():N}.json");
+
+        var copied = await new WebRootFiles().CopyToAsync("specs/eri/does-not-exist.json", destinationPath);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(copied, Is.False);
+            Assert.That(File.Exists(destinationPath), Is.False);
+        });
+    }
 }