using System;
using System.Drawing;
using System.Collections.Generic;
using System.Runtime.InteropServices;

// The 'windowHandle' parameter will contain the window handle for the:
//   - Active window when run by hotkey
//   - Window Location target when run by a Window Location rule
//   - TitleBar Button owner when run by a TitleBar Button
//   - Jump List owner when run from a Taskbar Jump List
//   - Currently focused window if none of these match
public static class DisplayFusionFunction
{
	public static void Run(IntPtr windowHandle)
	{
		//a list to store the potential windows
		List<IntPtr> windows = new List<IntPtr>();
		
		//get the current position of the mouse
		Point mousePosition = new Point(BFS.Input.GetMousePositionX(), BFS.Input.GetMousePositionY());
		
		//loop through all of the visible windows
		foreach(IntPtr window in BFS.Window.GetVisibleWindowHandles())
		{
			//skip any DisplayFusion window (title bar buttons, etc) or the search pane
			string windowClass = BFS.Window.GetClass(window);
			if(windowClass.StartsWith("DF", StringComparison.Ordinal) || 
			   windowClass.Equals("SearchPane", StringComparison.Ordinal) ||
			   windowClass.Equals("ImmersiveLauncher", StringComparison.Ordinal) ||
			   windowClass.Equals("Windows.UI.Core.CoreWindow", StringComparison.Ordinal) ||
               windowClass.Equals("WorkerW", StringComparison.Ordinal))		   
		   {
				continue;
		   }

		   //skip if this is the charms bar
			if(BFS.Window.GetText(window).Equals("Charm Bar", StringComparison.Ordinal))
				continue;
				
			//get the bounds of the window and see if the mouse is over it
			Rectangle bounds = BFS.Window.GetBounds(window);
			if(!bounds.Contains(mousePosition))
				continue;
				
			//if it's over it, add it to the potential windows
			windows.Add(window);
		}
		
		//we found no eligable windows, exit
		if(windows.Count == 0)
			return;
			
		//sort the windows by their z-order
		windows.Sort(ZOrderComparer.Instance);
		
		//the first window in the list should now be the topmost window.
		//focus and maximize it
		BFS.Window.Focus(windows[0]);
	}
	
	//this custom comparer will sort window handles by their z-order
	private class ZOrderComparer : IComparer<IntPtr>
	{
		//this function is needed to find the z-order of windows
		[DllImport("User32.dll", CharSet = CharSet.Unicode, ExactSpelling = true)]
		private static extern IntPtr GetWindow(IntPtr hWnd, GetWindowCommandEnum uCmd);
		
		//an enum so we can only put valid parameters into the GetWindow function
		private enum GetWindowCommandEnum : uint 
		{
			GW_CHILD = 5,
			GW_ENABLEDPOPUP = 6,
			GW_HWNDFIRST = 0,
			GW_HWNDLAST = 1,
			GW_HWNDNEXT = 2,
			GW_HWNDPREV = 3,
			GW_OWNER = 4,
		}
	
		//make it so this class only gets created once for the life of the script
		private static ZOrderComparer _Instance = null;
		internal static ZOrderComparer Instance 
		{
			get 
			{
				if(_Instance == null)
					_Instance = new ZOrderComparer();
					
				return _Instance;
			}
		}
		
		private ZOrderComparer(){}
		
		//a function that gets the z-order of windows. static to boost the speed a little
		private static int GetWindowZOrder(IntPtr handle)
		{
			int order = 0;
			for (IntPtr h = handle; h != IntPtr.Zero; h = GetWindow(h, GetWindowCommandEnum.GW_HWNDPREV))
				order++;
				
			return order;
		}
		
		//get the z-order of the windows and compare them
		public int Compare(IntPtr first, IntPtr second)
		{
			int z1 = GetWindowZOrder(first);
			int z2 = GetWindowZOrder(second);
			if(z1 > z2)
				return 1;
				
			if(z1 < z2)
				return -1;
				
			return 0;
		}
	}
}