using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace BrokerInterfaceETrade
{
   public sealed class ClipboardNotification : IDisposable
	{

		public const int WM_CLIPBOARDUPDATE = 0x031D;
		public static IntPtr HWND_MESSAGE = new IntPtr(-3);

		[DllImport("user32.dll", SetLastError = true)]
		[return: MarshalAs(UnmanagedType.Bool)]
		public static extern bool AddClipboardFormatListener(IntPtr hwnd);

		[DllImport("user32.dll", SetLastError = true)]
		[return: MarshalAs(UnmanagedType.Bool)]
		public static extern bool RemoveClipboardFormatListener(IntPtr hwnd);


		[DllImport("user32.dll", SetLastError = true)]
		public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

		public event EventHandler ClipboardUpdate;

		private readonly NotificationForm _form;

		public ClipboardNotification()
		{
			_form = new NotificationForm(OnClipboardUpdate);
		}

		private void OnClipboardUpdate()
		{
			ClipboardUpdate?.Invoke(null, EventArgs.Empty);
		}

		private class NotificationForm : Form
		{
			private readonly Action _onClipboardUpdate;

			public NotificationForm(Action onClipboardUpdate)
			{
				_onClipboardUpdate = onClipboardUpdate;
				SetParent(Handle, HWND_MESSAGE);
				AddClipboardFormatListener(Handle);
			}

			protected override void WndProc(ref Message m)
			{
				if (m.Msg == WM_CLIPBOARDUPDATE)
					_onClipboardUpdate?.Invoke();
				base.WndProc(ref m);
			}
		}

		private void ReleaseUnmanagedResources()
		{
			RemoveClipboardFormatListener(_form.Handle);
		}

		public void Dispose()
		{
			ReleaseUnmanagedResources();
			GC.SuppressFinalize(this);
		}

		~ClipboardNotification()
		{
			ReleaseUnmanagedResources();
		}
	}
}