using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace TopMostWindow
{
	// Win32API
	public class WinAPI
	{
		[StructLayout(LayoutKind.Sequential)]
		public struct RECT
		{
			int left;
			int top;
			int right;
			int bottom;
		}

		[StructLayout(LayoutKind.Sequential)]
		public struct WINDOWINFO
		{
			public uint cbSize;
			public RECT rcWindow;
			public RECT rcClient;
			public uint dwStyle;
			public uint dwExStyle;
			public uint dwWindowStatus;
			public uint cxWindowBorders;
			public uint cyWindowBorders;
			public ushort atomWindowType;
			public ushort wCreatorVersion;
		}

		[DllImport("user32.dll")]
		public extern static IntPtr GetForegroundWindow();

		[DllImport("user32.dll")]
		public extern static int GetWindowThreadProcessId(IntPtr hWnd, out int lpdwProcessId);

		[DllImport("user32.dll")]
		[return: MarshalAs(UnmanagedType.Bool)]
		public extern static bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);

		[DllImport("user32.dll")]
		public extern static int UnregisterHotKey(IntPtr hWnd, int id);

		[DllImport("user32.dll")]
		[return: MarshalAs(UnmanagedType.Bool)]
		public extern static bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int x, int y, int cx, int cy, uint uFlags);

		[DllImport("user32.dll")]
		[return: MarshalAs(UnmanagedType.Bool)]
		public extern static bool GetWindowInfo(IntPtr hwnd, ref WINDOWINFO pwi);

		// ホットキーで使用するフラグ
		public const int MOD_NONE = 0x0000;
		public const int MOD_ALT = 0x0001;
		public const int MOD_CONTROL = 0x0002;
		public const int MOD_SHIFT = 0x0004;
		public const int MOD_WIN = 0x0008;

		// ウィンドウメッセージの定数
		public const int WM_HOTKEY = 0x0312;

		// ウィンドウの位置の変更に関するフラグ
		public const uint SWP_NOSIZE = 0x0001;
		public const uint SWP_NOMOVE = 0x0002;
		public const uint SWP_SHOWWINDOW = 0x0040;

		// ウィンドウのZオーダーに関する定数
		public const int HWND_TOPMOST = -1;
		public const int HWND_NOTOPMOST = -2;

		// 拡張ウィンドウスタイルのフラグ
		public const int WS_EX_TOPMOST = 0x00000008;
	}

	public class TopMostHotKey
	{
		// ホットキーの識別ID
		public const int HOTKEY_ID = 0x0001;

		// ホットキーにするキーコード
		public const int MOD_KEY = WinAPI.MOD_NONE;
		public const int HOTKEY = (int)Keys.Pause;

		// 最前面にしたウィンドウ一覧
		private LinkedList<IntPtr> _topMostWindows = new LinkedList<IntPtr>();

		private NotifyIcon _icon = null;
		private IntPtr _hWind = IntPtr.Zero;

		// コンストラクタ
		public TopMostHotKey(IntPtr hWind, NotifyIcon icon)
		{
			_hWind = hWind;
			_icon = icon;
			WinAPI.RegisterHotKey(_hWind, HOTKEY_ID, MOD_KEY, HOTKEY);
		}

		// デストラクタ
		~TopMostHotKey()
		{
			WinAPI.UnregisterHotKey(_hWind, HOTKEY_ID);

			foreach( var hWnd in _topMostWindows ) {
				WinAPI.SetWindowPos(hWnd, (IntPtr)WinAPI.HWND_NOTOPMOST, 0, 0, 0, 0, WinAPI.SWP_SHOWWINDOW | WinAPI.SWP_NOMOVE | WinAPI.SWP_NOSIZE);
			}
		}

		// ウィンドウプロシージャ
		public void WndProc(ref Message m)
		{
			if( m.Msg == WinAPI.WM_HOTKEY ) {
				if( (int)m.WParam == HOTKEY_ID ) {
					ToggleTopMostWindow(GetActiveProcess());
				}
			}
		}

		// ウィンドウの最前面設定を切り替え
		public void ToggleTopMostWindow(Process process)
		{
			if( process == null ) return;

			IntPtr hWnd = process.MainWindowHandle;
			if( IsTopmost(hWnd) ) {
				if( !WinAPI.SetWindowPos(hWnd, (IntPtr)WinAPI.HWND_NOTOPMOST, 0, 0, 0, 0, WinAPI.SWP_SHOWWINDOW | WinAPI.SWP_NOMOVE | WinAPI.SWP_NOSIZE) ) return;
				_icon.BalloonTipText = "NoTopMost";
				_icon.BalloonTipIcon = ToolTipIcon.None;
				_topMostWindows.Remove(hWnd);
			}
			else {
				if( !WinAPI.SetWindowPos(hWnd, (IntPtr)WinAPI.HWND_TOPMOST, 0, 0, 0, 0, WinAPI.SWP_NOMOVE | WinAPI.SWP_NOSIZE) ) return;
				_icon.BalloonTipText = "TopMost";
				_icon.BalloonTipIcon = ToolTipIcon.Warning;
				_topMostWindows.AddLast(hWnd);
			}
			// タスクトレイアイコンからツールチップの表示する
			_icon.BalloonTipTitle = process.MainWindowTitle;
			_icon.ShowBalloonTip(10000);
		}

		// アクティブなプロセスを取得
		private Process GetActiveProcess()
		{
			IntPtr hWnd = WinAPI.GetForegroundWindow();
			int processId = 0;
			WinAPI.GetWindowThreadProcessId(hWnd, out processId);
			return Process.GetProcessById(processId);
		}

		// ウィンドウが最前面設定されているか
		private bool IsTopmost(IntPtr hWnd)
		{
			WinAPI.WINDOWINFO info = new WinAPI.WINDOWINFO();
			info.cbSize = (uint)Marshal.SizeOf(info);
			WinAPI.GetWindowInfo(hWnd, ref info);
			return (info.dwExStyle & WinAPI.WS_EX_TOPMOST) != 0;
		}
	}
}