Added export history feature

Signed-off-by: Ajay Nair <ajaypnair99@gmail.com>

src/Calculator/Views/HistoryList.xaml

@@ -176,6 +176,14 @@
                     Content=""
                     ToolTipService.ToolTip="{utils:ResourceString Name=ClearHistory/[using:Windows.UI.Xaml.Controls]ToolTipService/ToolTip}"
                     Visibility="{x:Bind Model.ItemsCount, Mode=OneWay, Converter={StaticResource ItemSizeToVisibilityNegationConverter}}"/>
+
+            <Button x:Name="ExportButton"
+                    Grid.Row="0"
+                    Style="{ThemeResource HistoryButtonStyle}"
+                    AutomationProperties.Name="Export History"
+                    Click="ExportButton_Click">
+                <SymbolIcon Symbol="Download"/>
+            </Button>
         </Grid>
     </Grid>
 </UserControl>

src/Calculator/Views/HistoryList.xaml.cs

@@ -1,6 +1,11 @@
 using CalculatorApp.ViewModel;
 using CalculatorApp.ViewModel.Common;
-
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+using Windows.Storage;
+using Windows.Storage.Pickers;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 
@@ -77,6 +82,71 @@ namespace CalculatorApp
                 Model.DeleteItem(swipedItem);
             }
         }
+
+        private async void ExportButton_Click(object sender, RoutedEventArgs e)
+        {
+            var history = (CalculatorApp.ViewModel.HistoryViewModel)this.DataContext;
+           
+
+            if (history.ItemsCount == 0)
+            {
+                return; // No history to export
+            }
+
+            Debug.WriteLine("Opening save picker");
+
+            var savePicker = new FileSavePicker
+            {
+                SuggestedStartLocation = PickerLocationId.DocumentsLibrary,
+                SuggestedFileName = "CalculatorHistory"
+            };
+
+            Debug.WriteLine("Adding choice");
+
+            savePicker.FileTypeChoices.Add("Plain Text", new List<string> { ".txt" });
+            savePicker.FileTypeChoices.Add("CSV File", new List<string> { ".csv" });
+
+            StorageFile file = await savePicker.PickSaveFileAsync();
+
+            if (file == null)
+            {
+                return; // User cancelled
+            }
+
+            try
+            {
+                var content = new StringBuilder();
+                bool isCsv = file.FileType.Equals(".csv", System.StringComparison.OrdinalIgnoreCase);
+
+                if (isCsv)
+                {
+                    content.AppendLine("Expression,Result");
+                }
+
+                foreach (var item in history.Items)
+                {
+                    if (isCsv)
+                    {
+                        // Escape quotes and commas for CSV
+                        var expression = item.Expression.Replace("\"", "\"\"");
+                        var result = item.Result.Replace("\"", "\"\"");
+                        content.AppendLine($"\"{expression}\",\"{result}\"");
+                    }
+                    else
+                    {
+                        content.AppendLine($"{item.Expression} = {item.Result}");
+                    }
+                }
+
+                await FileIO.WriteTextAsync(file, content.ToString());
+            }
+            catch (Exception ex)
+            {
+                // Log error and show user-friendly message
+                Debug.WriteLine($"Error exporting history: {ex.Message}");
+                // You might want to show a dialog here to inform the user
+            }
+        }
     }
 }