Added basic export and import feature

src/HopFrame.Web/Plugins/HopFramePlugin.cs

@@ -1,3 +1,34 @@
-namespace HopFrame.Web.Plugins;
+using HopFrame.Web.Components.Pages;
+using Microsoft.AspNetCore.Components.Forms;
+using Microsoft.JSInterop;
 
-public abstract class HopFramePlugin;
+namespace HopFrame.Web.Plugins;
+
+public abstract class HopFramePlugin {
+
+    /// <summary>
+    /// Downloads a file using a helper js function
+    /// </summary>
+    /// <param name="fileName">The name of the file</param>
+    /// <param name="data">The content of the file</param>
+    /// <param name="runtime">The js reference for invoking the function (Injectable)</param>
+    protected async Task DownloadFile(string fileName, byte[] data, IJSRuntime runtime) {
+        using var stream = new DotNetStreamReference(new MemoryStream(data));
+
+        await runtime.InvokeVoidAsync("downloadFileFromStream", fileName, stream);
+    }
+
+    protected Task<IBrowserFile> UploadFile(HopFrameTablePage targetPage, IJSRuntime runtime) {
+        var result = new TaskCompletionSource<IBrowserFile>();
+
+        targetPage.OnFileUpload = files => {
+            result.SetResult(files.First());
+            targetPage.OnFileUpload = null;
+            return Task.CompletedTask;
+        };
+
+        runtime.InvokeVoidAsync("triggerClick", targetPage.FileInputElement!.Element);
+        return result.Task;
+    }
+    
+}