using System;
using System.Drawing;
using System.Runtime.InteropServices;

namespace DM_Weight.util.TabTip
{
    internal enum TaskbarPosition
    {
        Unknown = -1,
        Left,
        Top,
        Right,
        Bottom,
    }

    internal sealed class Taskbar
    {
        private const string ClassName = "Shell_TrayWnd";

        public Rectangle Bounds { get; }

        public TaskbarPosition Position
        {
            get;
            private set;
        }

        public Point Location => Bounds.Location;

        public Size Size => Bounds.Size;
        
        //Always returns false under Windows 7
        public bool AlwaysOnTop
        {
            get;
            private set;
        }
        public bool AutoHide
        {
            get;
            private set;
        }

        public Taskbar()
        {
            IntPtr taskbarHandle = User32.FindWindow(ClassName, null);

            APPBARDATA data = new APPBARDATA
            {
                cbSize = (uint) Marshal.SizeOf(typeof (APPBARDATA)),
                hWnd = taskbarHandle
            };
            IntPtr result = Shell32.SHAppBarMessage(ABM.GetTaskbarPos, ref data);
            if (result != IntPtr.Zero)
            {
                Position = (TaskbarPosition) data.uEdge;
                Bounds = Rectangle.FromLTRB(data.rc.left, data.rc.top, data.rc.right, data.rc.bottom);

                data.cbSize = (uint) Marshal.SizeOf(typeof(APPBARDATA));
                result = Shell32.SHAppBarMessage(ABM.GetState, ref data);
                int state = result.ToInt32();
                AlwaysOnTop = (state & ABS.AlwaysOnTop) == ABS.AlwaysOnTop;
                AutoHide = (state & ABS.Autohide) == ABS.Autohide;
            }
            else
            {
                Position = TaskbarPosition.Unknown;
            }
        }

        private enum ABM : uint
        {
            New = 0x00000000,
            Remove = 0x00000001,
            QueryPos = 0x00000002,
            SetPos = 0x00000003,
            GetState = 0x00000004,
            GetTaskbarPos = 0x00000005,
            Activate = 0x00000006,
            GetAutoHideBar = 0x00000007,
            SetAutoHideBar = 0x00000008,
            WindowPosChanged = 0x00000009,
            SetState = 0x0000000A,
        }

        private enum ABE : uint
        {
            Left = 0,
            Top = 1,
            Right = 2,
            Bottom = 3
        }

        private static class ABS
        {
            public const int Autohide = 0x0000001;
            public const int AlwaysOnTop = 0x0000002;
        }

        private static class Shell32
        {
            [DllImport("shell32.dll", SetLastError = true)]
            public static extern IntPtr SHAppBarMessage(ABM dwMessage, [In] ref APPBARDATA pData);
        }

        private static class User32
        {
            [DllImport("user32.dll", SetLastError = true)]
            public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct APPBARDATA
        {
            public uint cbSize;
            public IntPtr hWnd;
            public uint uCallbackMessage;
            public ABE uEdge;
            public RECT rc;
            public int lParam;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }
    }
}