Wino-Mail/Wino.Calendar/Controls/WinoCalendarView.cs

using System;
using System.Windows.Input;
using CommunityToolkit.Diagnostics;
using Windows.UI;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Wino.Core.Domain.Models.Calendar;
using Wino.Helpers;

namespace Wino.Calendar.Controls;

public partial class WinoCalendarView : Control
{
    private const string PART_DayViewItemBorder = nameof(PART_DayViewItemBorder);
    private const string PART_CalendarView = nameof(PART_CalendarView);

    public static readonly DependencyProperty HighlightedDateRangeProperty = DependencyProperty.Register(nameof(HighlightedDateRange), typeof(DateRange), typeof(WinoCalendarView), new PropertyMetadata(null, new PropertyChangedCallback(OnHighlightedDateRangeChanged)));
    public static readonly DependencyProperty VisibleDateBackgroundProperty = DependencyProperty.Register(nameof(VisibleDateBackground), typeof(Brush), typeof(WinoCalendarView), new PropertyMetadata(null, new PropertyChangedCallback(OnPropertiesChanged)));
    public static readonly DependencyProperty DateClickedCommandProperty = DependencyProperty.Register(nameof(DateClickedCommand), typeof(ICommand), typeof(WinoCalendarView), new PropertyMetadata(null));
    public static readonly DependencyProperty TodayBackgroundColorProperty = DependencyProperty.Register(nameof(TodayBackgroundColor), typeof(Color), typeof(WinoCalendarView), new PropertyMetadata(null));

    public Color TodayBackgroundColor
    {
        get { return (Color)GetValue(TodayBackgroundColorProperty); }
        set { SetValue(TodayBackgroundColorProperty, value); }
    }

    /// <summary>
    /// Gets or sets the command to execute when a date is picked.
    /// Unused.
    /// </summary>
    public ICommand DateClickedCommand
    {
        get { return (ICommand)GetValue(DateClickedCommandProperty); }
        set { SetValue(DateClickedCommandProperty, value); }
    }

    /// <summary>
    /// Gets or sets the highlighted range of dates.
    /// </summary>
    public DateRange HighlightedDateRange
    {
        get { return (DateRange)GetValue(HighlightedDateRangeProperty); }
        set { SetValue(HighlightedDateRangeProperty, value); }
    }

    public Brush VisibleDateBackground
    {
        get { return (Brush)GetValue(VisibleDateBackgroundProperty); }
        set { SetValue(VisibleDateBackgroundProperty, value); }
    }



    private CalendarView CalendarView;

    public WinoCalendarView()
    {
        DefaultStyleKey = typeof(WinoCalendarView);
    }

    protected override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        CalendarView = GetTemplateChild(PART_CalendarView) as CalendarView;

        Guard.IsNotNull(CalendarView, nameof(CalendarView));

        CalendarView.SelectedDatesChanged -= InternalCalendarViewSelectionChanged;
        CalendarView.SelectedDatesChanged += InternalCalendarViewSelectionChanged;

        // TODO: Should come from settings.
        CalendarView.FirstDayOfWeek = Windows.Globalization.DayOfWeek.Monday;

        // Everytime display mode changes, update the visible date range backgrounds.
        // If users go back from year -> month -> day, we need to update the visible date range backgrounds.

        CalendarView.RegisterPropertyChangedCallback(CalendarView.DisplayModeProperty, (s, e) => UpdateVisibleDateRangeBackgrounds());
    }

    private void InternalCalendarViewSelectionChanged(CalendarView sender, CalendarViewSelectedDatesChangedEventArgs args)
    {
        if (args.AddedDates?.Count > 0)
        {
            var clickedDate = args.AddedDates[0].Date;
            SetInnerDisplayDate(clickedDate);

            var clickArgs = new CalendarViewDayClickedEventArgs(clickedDate);
            DateClickedCommand?.Execute(clickArgs);
        }

        // Reset selection, we don't show selected dates but react to them.
        CalendarView.SelectedDates.Clear();
    }

    private static void OnPropertiesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is WinoCalendarView control)
        {
            control.UpdateVisibleDateRangeBackgrounds();
        }
    }

    private void SetInnerDisplayDate(DateTime dateTime) => CalendarView?.SetDisplayDate(dateTime);

    // Changing selected dates will trigger the selection changed event.
    // It will behave like user clicked the date.
    public void GoToDay(DateTime dateTime) => CalendarView.SelectedDates.Add(dateTime);

    private static void OnHighlightedDateRangeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is WinoCalendarView control)
        {
            control.SetInnerDisplayDate(control.HighlightedDateRange.StartDate);
            control.UpdateVisibleDateRangeBackgrounds();
        }
    }

    public void UpdateVisibleDateRangeBackgrounds()
    {
        if (HighlightedDateRange == null || VisibleDateBackground == null || TodayBackgroundColor == null || CalendarView == null) return;

        var markDateCalendarDayItems = WinoVisualTreeHelper.FindDescendants<CalendarViewDayItem>(CalendarView);

        foreach (var calendarDayItem in markDateCalendarDayItems)
        {
            var border = WinoVisualTreeHelper.GetChildObject<Border>(calendarDayItem, PART_DayViewItemBorder);

            if (border == null) return;

            if (calendarDayItem.Date.Date == DateTime.Today.Date)
            {
                border.Background = new SolidColorBrush(TodayBackgroundColor);
            }
            else if (calendarDayItem.Date.Date >= HighlightedDateRange.StartDate.Date && calendarDayItem.Date.Date < HighlightedDateRange.EndDate.Date)
            {
                border.Background = VisibleDateBackground;
            }
            else
            {
                border.Background = null;
            }
        }
    }
}