feat: disabled date related feature.

src/Ursa/Controls/DateTimePicker/Calendar.cs

@@ -1,4 +1,5 @@
 using Avalonia;
+using Avalonia.Collections;
 using Avalonia.Controls.Primitives;
 using Avalonia.Interactivity;
 
@@ -12,8 +13,10 @@ public class Calendar: TemplatedControl
         get => GetValue(SelectedDateProperty);
         set => SetValue(SelectedDateProperty, value);
     }
-    
-    public static readonly StyledProperty<DayOfWeek> FirstDayOfWeekProperty = AvaloniaProperty.Register<Calendar, DayOfWeek>(nameof(FirstDayOfWeek), DayOfWeek.Sunday);
+
+    public static readonly StyledProperty<DayOfWeek> FirstDayOfWeekProperty =
+        AvaloniaProperty.Register<Calendar, DayOfWeek>(nameof(FirstDayOfWeek),
+            defaultValue: DateTimeHelper.GetCurrentDateTimeFormatInfo().FirstDayOfWeek);
     public DayOfWeek FirstDayOfWeek
     {
         get => GetValue(FirstDayOfWeekProperty);
@@ -26,4 +29,23 @@ public class Calendar: TemplatedControl
         get => GetValue(IsTodayHighlightedProperty);
         set => SetValue(IsTodayHighlightedProperty, value);
     }
+
+    public static readonly StyledProperty<AvaloniaList<DateRange>?> DisabledDatesProperty =
+        AvaloniaProperty.Register<Calendar, AvaloniaList<DateRange>?>(
+            nameof(DisabledDates));
+
+    public AvaloniaList<DateRange>? DisabledDates
+    {
+        get => GetValue(DisabledDatesProperty);
+        set => SetValue(DisabledDatesProperty, value);
+    }
+
+    public static readonly StyledProperty<IDateSelector?> DisabledDateRuleProperty = AvaloniaProperty.Register<Calendar, IDateSelector?>(
+        nameof(DisabledDateRule));
+
+    public IDateSelector? DisabledDateRule
+    {
+        get => GetValue(DisabledDateRuleProperty);
+        set => SetValue(DisabledDateRuleProperty, value);
+    }
 }

src/Ursa/Controls/DateTimePicker/CalendarDayButton.cs

@@ -0,0 +1,8 @@
+using Avalonia.Controls;
+
+namespace Ursa.Controls;
+
+public class CalendarDayButton: Button
+{
+    
+}

src/Ursa/Controls/DateTimePicker/DateRange.cs

@@ -0,0 +1,36 @@
+namespace Ursa.Controls;
+
+/// <summary>
+///     Represents a date range. It can be a single day or a range of days. The range is inclusive.
+/// </summary>
+public sealed record DateRange
+{
+    public DateRange(DateTime day)
+    {
+        Start = day.Date;
+        End = day.Date;
+    }
+
+    public DateRange(DateTime start, DateTime end)
+    {
+        if (DateTime.Compare(end, start) >= 0)
+        {
+            Start = start.Date;
+            End = end.Date;
+        }
+        else
+        {
+            Start = start.Date;
+            End = start.Date;
+        }
+    }
+
+    public DateTime Start { get; private set; }
+    public DateTime End { get; private set; }
+
+    public bool Contains(DateTime? date)
+    {
+        if (date is null) return false;
+        return date >= Start && date <= End;
+    }
+}

src/Ursa/Controls/DateTimePicker/DateTimeHelper.cs

@@ -0,0 +1,17 @@
+using System.Globalization;
+
+namespace Ursa.Controls;
+
+internal static class DateTimeHelper
+{
+    public static DateTimeFormatInfo GetCurrentDateTimeFormatInfo()
+    {
+        if (CultureInfo.CurrentCulture.Calendar is GregorianCalendar) return CultureInfo.CurrentCulture.DateTimeFormat;
+        System.Globalization.Calendar? calendar =
+            CultureInfo.CurrentCulture.OptionalCalendars.OfType<GregorianCalendar>().FirstOrDefault();
+        string cultureName = calendar is null ? CultureInfo.InvariantCulture.Name : CultureInfo.CurrentCulture.Name;
+        var dt = new CultureInfo(cultureName).DateTimeFormat;
+        dt.Calendar = calendar ?? new GregorianCalendar();
+        return dt;
+    }
+}

src/Ursa/Controls/DateTimePicker/IDateSelector.cs

@@ -0,0 +1,17 @@
+namespace Ursa.Controls;
+
+public interface IDateSelector
+{
+    public bool IsValid(DateTime? date); 
+}
+
+public class WeekendDateSelector: IDateSelector
+{
+    public static WeekendDateSelector Instance { get; } = new WeekendDateSelector();
+    
+    public bool IsValid(DateTime? date)
+    {
+        if (date is null) return false;
+        return date.Value.DayOfWeek == DayOfWeek.Saturday || date.Value.DayOfWeek == DayOfWeek.Sunday;
+    }
+}