using System.Windows.Controls;
using System.Windows;
using System.Windows.Media;
using System.Windows.Markup;

namespace Minesweeper {

	[ContentProperty("Child")]
	public class Viewbox: Control {

		public static DependencyProperty ChildProperty = DependencyProperty.Register("Child", typeof(FrameworkElement), typeof(Viewbox), Viewbox.ChildChanged);

		private Panel childHost;
		private ScaleTransform scale;
		private TranslateTransform offset;

		public Viewbox() {

			// Inlining the template to make the file standalone. 
			// It's not intended to be retemplated.
			string templateXaml = @"<ControlTemplate xmlns='http://schemas.microsoft.com/client/2007' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'>
										<Canvas x:Name='ELEMENT_ChildHost'/>
									</ControlTemplate>";
			this.Template = (ControlTemplate)XamlReader.Load(templateXaml);
		}

		public FrameworkElement Child {
			get { return (FrameworkElement)this.GetValue(Viewbox.ChildProperty); }
			set { this.SetValue(Viewbox.ChildProperty, value); }
		}

		private static void ChildChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e) {
			((Viewbox)sender).OnChildChanged(e);
		}

		protected virtual void OnChildChanged(DependencyPropertyChangedEventArgs e) {
			if (e.OldValue != null && this.childHost != null)
				this.childHost.Children.Remove((FrameworkElement)e.OldValue);
			if (e.NewValue != null && this.childHost != null)
				this.childHost.Children.Add((FrameworkElement)e.NewValue);
		}

		protected override Size ArrangeOverride(Size finalSize) {

			double scaleX = finalSize.Width / this.Child.DesiredSize.Width;
			double scaleY = finalSize.Height / this.Child.DesiredSize.Height;

			if (scaleX > scaleY) {
				this.scale.ScaleX = this.scale.ScaleY = scaleY;

				this.offset.X = (finalSize.Width - this.Child.DesiredSize.Width * scaleY) / 2;
				this.offset.Y = 0;
			}
			else {
				this.scale.ScaleX = this.scale.ScaleY = scaleX;

				this.offset.Y = (finalSize.Height - this.Child.DesiredSize.Height * scaleX) / 2;
				//this.offset.X = 0;
			}

			this.Child.Arrange(new Rect(0, 0, this.Child.DesiredSize.Width, this.Child.DesiredSize.Height));

			return finalSize;
		}

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

			this.childHost = this.GetTemplateChild("ELEMENT_ChildHost") as Panel;

			this.scale = new ScaleTransform();
			this.offset = new TranslateTransform();

			TransformGroup transform = new TransformGroup();
			transform.Children.Add(this.scale);
			transform.Children.Add(this.offset);
			

			this.childHost.RenderTransform = transform;

			if (this.Child != null)
				this.childHost.Children.Add(this.Child);
		}


	}
}