Merge core project into winui project.

Wino.Mail.WinUI/Services/UnderlyingThemeService.cs

@@ -0,0 +1,28 @@
+using Windows.UI.ViewManagement;
+using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
+
+namespace Wino.Mail.WinUI.Services;
+
+public class UnderlyingThemeService : IUnderlyingThemeService
+{
+    public const string SelectedAppThemeKey = nameof(SelectedAppThemeKey);
+
+    private readonly UISettings uiSettings = new UISettings();
+    private readonly IConfigurationService _configurationService;
+
+    public UnderlyingThemeService(IConfigurationService configurationService)
+    {
+        _configurationService = configurationService;
+    }
+
+    public bool IsUnderlyingThemeDark()
+    {
+        var currentTheme = _configurationService.Get(SelectedAppThemeKey, ApplicationElementTheme.Default);
+
+        if (currentTheme == ApplicationElementTheme.Default)
+            return uiSettings.GetColorValue(UIColorType.Background).ToString() == "#FF000000";
+        else
+            return currentTheme == ApplicationElementTheme.Dark;
+    }
+}