Add ability to import FastFlags from JSON

Bloxstrap/UI/Elements/Menu/Pages/FastFlagEditorPage.xaml

@@ -34,6 +34,7 @@
                 </ui:Button.Style>
             </ui:Button>
             <ToggleButton x:Name="TogglePresetsButton" Content="Show preset flags" Click="ToggleButton_Click" Margin="12,0,0,0" />
+            <ui:Button Icon="ArrowImport24" Content="Import JSON" Margin="12,0,0,0" Click="ImportJSONButton_Click" />
         </StackPanel>
 
         <ui:TextBox x:Name="SearchTextBox" Grid.Row="2" Margin="0,0,0,16" Icon="Search32" PlaceholderText="Search" TextChanged="SearchTextBox_TextChanged" />

Bloxstrap/UI/Elements/Menu/Pages/FastFlagEditorPage.xaml.cs

@@ -3,6 +3,8 @@ using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Controls.Primitives;
 
+using Microsoft.Win32;
+
 using Wpf.Ui.Mvvm.Contracts;
 
 using Bloxstrap.UI.Elements.Dialogs;
@@ -211,6 +213,63 @@ namespace Bloxstrap.UI.Elements.Menu.Pages
             ReloadList();
         }
 
+        private void ImportJSONButton_Click(object sender, RoutedEventArgs e)
+        {
+            var dialog = new OpenFileDialog
+            {
+                Filter = "JSON files|*.json|All files|*.*"
+            };
+
+            if (dialog.ShowDialog() != true)
+                return;
+
+            try
+            {
+                var list = JsonSerializer.Deserialize<Dictionary<string, object>>(File.ReadAllText(dialog.FileName));
+
+                if (list is null)
+                    throw new Exception("JSON deserialization returned null");
+
+                var conflictingFlags = App.FastFlags.Prop.Where(x => list.ContainsKey(x.Key)).Select(x => x.Key);
+                bool overwriteConflicting = false;
+
+                if (conflictingFlags.Any())
+                {
+                    var result = Controls.ShowMessageBox(
+                        "Some of the flags you are attempting to import already have set values. Would you like to overwrite their current values with the ones defined in the import?\n" +
+                        "\n" +
+                        "Conflicting flags:\n" +
+                        String.Join(", ", conflictingFlags),
+                        MessageBoxImage.Question,
+                        MessageBoxButton.YesNo
+                    );
+
+                    overwriteConflicting = result == MessageBoxResult.Yes;
+                }
+
+                foreach (var pair in list)
+                {
+                    if (App.FastFlags.Prop.ContainsKey(pair.Key) && !overwriteConflicting)
+                        continue;
+
+                    App.FastFlags.SetValue(pair.Key, pair.Value);
+                }
+
+                _searchFilter = "";
+                ReloadList();
+            }
+            catch (Exception ex)
+            {
+                Controls.ShowMessageBox(
+                    "The file you've selected does not appear to be valid JSON. Please double check the file contents and try again.\n" +
+                    "\n" + 
+                    "More information:\n" +
+                    $"{ex.Message}",
+                    MessageBoxImage.Error
+                );
+            }
+        }
+
         private void SearchTextBox_TextChanged(object sender, TextChangedEventArgs e)
         {
             if (sender is not TextBox textbox)