using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Data;
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

namespace App1
{
	internal partial class FlowDirectionManager : DependencyObject, INotifyPropertyChanged
	{
		public FlowDirection FlowDirection
		{
			get { return (FlowDirection)GetValue(FDTargetProperty); }
			set { SetValue(FDTargetProperty, value); }
		}
		public static readonly DependencyProperty FDTargetProperty =
			DependencyProperty.Register("FlowDirection", typeof(FlowDirection), typeof(FlowDirectionManager), new PropertyMetadata(FlowDirection.LeftToRight));

		public Binding CreateBindingToFlowDirection(FrameworkElement target)
		{
			var binding = new Binding
			{
				Source = this,
				Path = new PropertyPath("FlowDirection"),
				Mode = BindingMode.OneWay
			};
			target.SetBinding(FrameworkElement.FlowDirectionProperty, binding);
			return binding;
		}

		public void SetFlowMode(IntPtr hwnd, FlowDirection fd)
		{
			// Hard coded for testing, should use original value
			var niStyle = 0x0000000000000100;

			if (fd == FlowDirection.RightToLeft)
			{
				niStyle |= WS_EX_LAYOUTRTL;
			}

			SetWindowLongPtr(hwnd, GWL_EXSTYLE, niStyle);
			SetProcessDefaultLayout(fd == FlowDirection.LeftToRight ? (uint)0 : 1);
			FlowDirection = fd;
			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("FlowDirection"));
		}

		// Native APIs

		const int GWL_EXSTYLE = -20;
		const int WS_EX_LAYOUTRTL = 0x00400000;

		public event PropertyChangedEventHandler? PropertyChanged;

		[DllImport("user32.dll", SetLastError = true)]
		public static extern bool SetProcessDefaultLayout(uint dwDefaultLayout);

		[DllImport("user32.dll", SetLastError = true)]
		static extern IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
	}
}