using System.Windows.Documents;


namespace Melskin.Controls;
#region Internal Implementation

internal class WindowHost : IToastHost
{
    private readonly StackPanel toastContainer;

    public WindowHost(Window window)
    {
        toastContainer = new StackPanel();

        // Use a style to apply margin between toasts, which is a robust approach.
        var childStyle = new Style(typeof(ToastControl));
        childStyle.Setters.Add(new Setter(FrameworkElement.MarginProperty, new Thickness(0, 8, 0, 8)));
        toastContainer.Resources.Add(typeof(ToastControl), childStyle);

        var adornerLayer = AdornerLayer.GetAdornerLayer(window.Content as Visual);
        if (adornerLayer == null) throw new InvalidOperationException("在指定的窗口中找不到 AdornerLayer。");

        adornerLayer.Add(new ToastAdorner(window.Content as UIElement, toastContainer));
    }

    public void AddToast(ToastControl toast) => toastContainer.Children.Add(toast);
    public void RemoveToast(ToastControl toast) => toastContainer.Children.Remove(toast);


    private class ToastAdorner : Adorner
    {
        private readonly UIElement child; // This is our StackPanel

        public ToastAdorner(UIElement? adornedElement, UIElement child) : base(adornedElement)
        {
            this.child = child;
            // Add the child to the visual tree. This is essential.
            AddVisualChild(this.child);
        }

        protected override int VisualChildrenCount => 1;
        protected override Visual GetVisualChild(int index) => child;

        // We override Measure to tell our child (StackPanel) how much space it has.
        protected override Size MeasureOverride(Size constraint)
        {
            // Give the child all the space it could possibly want.
            // It will then measure itself and its children, establishing its DesiredSize.
            child.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
            // The Adorner itself doesn't need to return a specific size, as it's a transparent overlay.
            return base.MeasureOverride(constraint);
        }

        // ArrangeOverride is where we do the actual positioning.
        protected override Size ArrangeOverride(Size finalSize)
        {
            // 'finalSize' is the full size of the element we are adorning (e.g., the window's content area).
            // '_child.DesiredSize' is the size our StackPanel reported it needs after being measured.

            // Calculate the X coordinate to center the child (StackPanel).
            var x = (finalSize.Width - child.DesiredSize.Width) / 2;

            // The Y coordinate is 0, placing it at the very top.
            double y = 0;

            // Create the final rectangle for our child, positioned correctly.
            var finalRect = new Rect(new Point(x, y), child.DesiredSize);

            // Arrange the child (our StackPanel) in the calculated centered rectangle.
            child.Arrange(finalRect);

            // The Adorner itself arranges to fill the entire space.
            return finalSize;
        }
    }
}
#endregion