gui-cs.Terminal.Gui/Terminal.Gui/ConsoleDrivers/WindowsDriver/WindowsConsole.cs

#nullable enable
using System.Collections.Concurrent;
using System.ComponentModel;
using System.Runtime.InteropServices;
using Terminal.Gui.ConsoleDrivers;

namespace Terminal.Gui;

internal class WindowsConsole
{
    private CancellationTokenSource? _inputReadyCancellationTokenSource;
    private readonly BlockingCollection<InputRecord> _inputQueue = new (new ConcurrentQueue<InputRecord> ());
    internal WindowsMainLoop? _mainLoop;

    public const int STD_OUTPUT_HANDLE = -11;
    public const int STD_INPUT_HANDLE = -10;

    private readonly nint _inputHandle;
    private nint _outputHandle;
    //private nint _screenBuffer;
    private readonly uint _originalConsoleMode;
    private CursorVisibility? _initialCursorVisibility;
    private CursorVisibility? _currentCursorVisibility;
    private CursorVisibility? _pendingCursorVisibility;
    private readonly StringBuilder _stringBuilder = new (256 * 1024);
    private string _lastWrite = string.Empty;

    public WindowsConsole ()
    {
        _inputHandle = GetStdHandle (STD_INPUT_HANDLE);
        _outputHandle = GetStdHandle (STD_OUTPUT_HANDLE);
        _originalConsoleMode = ConsoleMode;
        uint newConsoleMode = _originalConsoleMode;
        newConsoleMode |= (uint)(ConsoleModes.EnableMouseInput | ConsoleModes.EnableExtendedFlags);
        newConsoleMode &= ~(uint)ConsoleModes.EnableQuickEditMode;
        newConsoleMode &= ~(uint)ConsoleModes.EnableProcessedInput;
        ConsoleMode = newConsoleMode;

        _inputReadyCancellationTokenSource = new ();
        Task.Run (ProcessInputQueue, _inputReadyCancellationTokenSource.Token);
    }

    public InputRecord? DequeueInput ()
    {
        while (_inputReadyCancellationTokenSource is { })
        {
            try
            {
                return _inputQueue.Take (_inputReadyCancellationTokenSource.Token);
            }
            catch (OperationCanceledException)
            {
                return null;
            }
        }

        return null;
    }

    public InputRecord? ReadConsoleInput ()
    {
        const int BUFFER_SIZE = 1;
        InputRecord inputRecord = default;
        uint numberEventsRead = 0;
        StringBuilder ansiSequence = new StringBuilder ();
        bool readingSequence = false;
        bool raisedResponse = false;

        while (!_inputReadyCancellationTokenSource!.IsCancellationRequested)
        {
            try
            {
                // Peek to check if there is any input available
                if (PeekConsoleInput (_inputHandle, out _, BUFFER_SIZE, out uint eventsRead) && eventsRead > 0)
                {
                    // Read the input since it is available
                    ReadConsoleInput (
                                      _inputHandle,
                                      out inputRecord,
                                      BUFFER_SIZE,
                                      out numberEventsRead);

                    if (inputRecord.EventType == EventType.Key)
                    {
                        KeyEventRecord keyEvent = inputRecord.KeyEvent;

                        if (keyEvent.bKeyDown)
                        {
                            char inputChar = keyEvent.UnicodeChar;

                            // Check if input is part of an ANSI escape sequence
                            if (inputChar == '\u001B') // Escape character
                            {
                                // Peek to check if there is any input available with key event and bKeyDown and not Escape character
                                if (PeekConsoleInput (_inputHandle, out InputRecord peekRecord, BUFFER_SIZE, out eventsRead) && eventsRead > 0)
                                {
                                    if (peekRecord is { EventType: EventType.Key, KeyEvent.bKeyDown: true, KeyEvent.UnicodeChar: not '\u001B' })
                                    {
                                        // It's really an ANSI request response
                                        readingSequence = true;
                                        // Start a new sequence ensuring in the cases where wasn't clear by reading the terminator
                                        ansiSequence.Clear ();
                                        ansiSequence.Append (inputChar);

                                        continue;
                                    }
                                }
                            }
                            else if (readingSequence)
                            {
                                ansiSequence.Append (inputChar);

                                // Check if the sequence has ended with an expected command terminator
                                if (AnsiEscapeSequenceRequests.HasResponse (inputChar.ToString (), out AnsiEscapeSequenceRequestStatus? seqReqStatus))
                                {
                                    // Finished reading the sequence and remove the enqueued request
                                    AnsiEscapeSequenceRequests.Remove (seqReqStatus);

                                    lock (seqReqStatus!.AnsiRequest._responseLock)
                                    {
                                        readingSequence = false;
                                        raisedResponse = true;
                                        seqReqStatus.AnsiRequest.RaiseResponseFromInput (ansiSequence.ToString ());
                                        // Clear the terminator for not be enqueued
                                        inputRecord = default (InputRecord);
                                        // Clear numberEventsRead to not exit
                                        numberEventsRead = 0;
                                        // Clear the ansiSequence to avoid insert another Esc character
                                        ansiSequence.Clear ();
                                    }
                                }

                                if (readingSequence)
                                {
                                    continue;
                                }
                            }
                        }
                    }
                }

                if (readingSequence && !raisedResponse && AnsiEscapeSequenceRequestUtils.IncompleteCkInfos is null && AnsiEscapeSequenceRequests.Statuses.Count > 0)
                {
                    AnsiEscapeSequenceRequests.Statuses.TryDequeue (out AnsiEscapeSequenceRequestStatus? seqReqStatus);

                    lock (seqReqStatus!.AnsiRequest._responseLock)
                    {
                        seqReqStatus.AnsiRequest.RaiseResponseFromInput (ansiSequence.ToString ());
                        // Clear the terminator for not be enqueued
                        inputRecord = default (InputRecord);
                    }

                    _retries = 0;
                }
                else if (AnsiEscapeSequenceRequestUtils.IncompleteCkInfos is null && AnsiEscapeSequenceRequests.Statuses.Count > 0)
                {
                    if (_retries > 1)
                    {
                        if (AnsiEscapeSequenceRequests.Statuses.TryPeek (out AnsiEscapeSequenceRequestStatus? seqReqStatus) && string.IsNullOrEmpty (seqReqStatus.AnsiRequest.AnsiEscapeSequenceResponse?.Response))
                        {
                            lock (seqReqStatus.AnsiRequest._responseLock)
                            {
                                AnsiEscapeSequenceRequests.Statuses.TryDequeue (out _);

                                seqReqStatus.AnsiRequest.RaiseResponseFromInput (null);
                                // Clear the terminator for not be enqueued
                                inputRecord = default (InputRecord);
                            }
                        }

                        _retries = 0;
                    }
                    else
                    {
                        _retries++;
                    }
                }
                else
                {
                    _retries = 0;
                }

                if (numberEventsRead > 0)
                {
                    return inputRecord;
                }

                if (!_forceRead)
                {
                    try
                    {
                        Task.Delay (100, _inputReadyCancellationTokenSource.Token).Wait (_inputReadyCancellationTokenSource.Token);
                    }
                    catch (OperationCanceledException)
                    {
                        return null;
                    }
                }
            }
            catch (Exception ex)
            {
                if (ex is OperationCanceledException or ObjectDisposedException)
                {
                    return null;
                }

                throw;
            }
        }

        return null;
    }

    internal bool _forceRead;

    private void ProcessInputQueue ()
    {
        while (_inputReadyCancellationTokenSource is { IsCancellationRequested: false })
        {
            try
            {
                if (_inputQueue.Count == 0 || _forceRead)
                {
                    while (_inputReadyCancellationTokenSource is { IsCancellationRequested: false })
                    {
                        try
                        {
                            InputRecord? inpRec = ReadConsoleInput ();

                            if (inpRec is { })
                            {
                                _inputQueue.Add (inpRec.Value);

                                break;
                            }
                        }
                        catch (OperationCanceledException)
                        {
                            return;
                        }
                    }
                }
            }
            catch (OperationCanceledException)
            {
                return;
            }
        }
    }


    private CharInfo []? _originalStdOutChars;

    public bool WriteToConsole (Size size, ExtendedCharInfo [] charInfoBuffer, Coord bufferSize, SmallRect window, bool force16Colors)
    {
        //Debug.WriteLine ("WriteToConsole");

        //if (_screenBuffer == nint.Zero)
        //{
        //    ReadFromConsoleOutput (size, bufferSize, ref window);
        //}

        var result = false;

        if (force16Colors)
        {
            var i = 0;
            CharInfo [] ci = new CharInfo [charInfoBuffer.Length];

            foreach (ExtendedCharInfo info in charInfoBuffer)
            {
                ci [i++] = new CharInfo
                {
                    Char = new CharUnion { UnicodeChar = info.Char },
                    Attributes =
                        (ushort)((int)info.Attribute.Foreground.GetClosestNamedColor16 () | ((int)info.Attribute.Background.GetClosestNamedColor16 () << 4))
                };
            }

            result = WriteConsoleOutput (_outputHandle, ci, bufferSize, new Coord { X = window.Left, Y = window.Top }, ref window);
        }
        else
        {
            _stringBuilder.Clear ();

            _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_SaveCursorPosition);
            _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_SetCursorPosition (0, 0));

            Attribute? prev = null;

            foreach (ExtendedCharInfo info in charInfoBuffer)
            {
                Attribute attr = info.Attribute;

                if (attr != prev)
                {
                    prev = attr;
                    _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_SetForegroundColorRGB (attr.Foreground.R, attr.Foreground.G, attr.Foreground.B));
                    _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_SetBackgroundColorRGB (attr.Background.R, attr.Background.G, attr.Background.B));
                }

                if (info.Char != '\x1b')
                {
                    if (!info.Empty)
                    {
                        _stringBuilder.Append (info.Char);
                    }
                }
                else
                {
                    _stringBuilder.Append (' ');
                }
            }

            _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_RestoreCursorPosition);
            _stringBuilder.Append (AnsiEscapeSequenceRequestUtils.CSI_HideCursor);

            var s = _stringBuilder.ToString ();

            // TODO: requires extensive testing if we go down this route
            // If console output has changed
            if (s != _lastWrite)
            {
                // supply console with the new content
                result = WriteConsole (_outputHandle, s, (uint)s.Length, out uint _, nint.Zero);
            }

            _lastWrite = s;

            foreach (var sixel in Application.Sixel)
            {
                SetCursorPosition (new Coord ((short)sixel.ScreenPosition.X, (short)sixel.ScreenPosition.Y));
                WriteConsole (_outputHandle, sixel.SixelData, (uint)sixel.SixelData.Length, out uint _, nint.Zero);
            }
        }

        if (!result)
        {
            int err = Marshal.GetLastWin32Error ();

            if (err != 0)
            {
                throw new Win32Exception (err);
            }
        }

        return result;
    }

    internal bool WriteANSI (string ansi)
    {
        if (WriteConsole (_outputHandle, ansi, (uint)ansi.Length, out uint _, nint.Zero))
        {
            // Flush the output to make sure it's sent immediately
            return FlushFileBuffers (_outputHandle);
        }

        return false;
    }

    public void ReadFromConsoleOutput (Size size, Coord coords, ref SmallRect window)
    {
        //_screenBuffer = CreateConsoleScreenBuffer (
        //                                           DesiredAccess.GenericRead | DesiredAccess.GenericWrite,
        //                                           ShareMode.FileShareRead | ShareMode.FileShareWrite,
        //                                           nint.Zero,
        //                                           1,
        //                                           nint.Zero
        //                                          );

        //if (_screenBuffer == INVALID_HANDLE_VALUE)
        //{
        //    int err = Marshal.GetLastWin32Error ();

        //    if (err != 0)
        //    {
        //        throw new Win32Exception (err);
        //    }
        //}

        SetInitialCursorVisibility ();

        //if (!SetConsoleActiveScreenBuffer (_screenBuffer))
        //{
        //    throw new Win32Exception (Marshal.GetLastWin32Error ());
        //}

        _originalStdOutChars = new CharInfo [size.Height * size.Width];

        if (!ReadConsoleOutput (_outputHandle, _originalStdOutChars, coords, new Coord { X = 0, Y = 0 }, ref window))
        {
            throw new Win32Exception (Marshal.GetLastWin32Error ());
        }
    }

    public bool SetCursorPosition (Coord position)
    {
        return SetConsoleCursorPosition (_outputHandle, position);
    }

    public void SetInitialCursorVisibility ()
    {
        if (_initialCursorVisibility.HasValue == false && GetCursorVisibility (out CursorVisibility visibility))
        {
            _initialCursorVisibility = visibility;
        }
    }

    public bool GetCursorVisibility (out CursorVisibility visibility)
    {
        if (_outputHandle == nint.Zero)
        {
            visibility = CursorVisibility.Invisible;

            return false;
        }

        if (!GetConsoleCursorInfo (_outputHandle, out ConsoleCursorInfo info))
        {
            int err = Marshal.GetLastWin32Error ();

            if (err != 0)
            {
                throw new Win32Exception (err);
            }

            visibility = CursorVisibility.Default;

            return false;
        }

        if (!info.bVisible)
        {
            visibility = CursorVisibility.Invisible;
        }
        else if (info.dwSize > 50)
        {
            visibility = CursorVisibility.Default;
        }
        else
        {
            visibility = CursorVisibility.Default;
        }

        return true;
    }

    public bool EnsureCursorVisibility ()
    {
        if (_initialCursorVisibility.HasValue && _pendingCursorVisibility.HasValue && SetCursorVisibility (_pendingCursorVisibility.Value))
        {
            _pendingCursorVisibility = null;

            return true;
        }

        return false;
    }

    public void ForceRefreshCursorVisibility ()
    {
        if (_currentCursorVisibility.HasValue)
        {
            _pendingCursorVisibility = _currentCursorVisibility;
            _currentCursorVisibility = null;
        }
    }

    public bool SetCursorVisibility (CursorVisibility visibility)
    {
        if (_initialCursorVisibility.HasValue == false)
        {
            _pendingCursorVisibility = visibility;

            return false;
        }

        if (_currentCursorVisibility.HasValue == false || _currentCursorVisibility.Value != visibility)
        {
            var info = new ConsoleCursorInfo
            {
                dwSize = (uint)visibility & 0x00FF,
                bVisible = ((uint)visibility & 0xFF00) != 0
            };

            if (!SetConsoleCursorInfo (_outputHandle, ref info))
            {
                return false;
            }

            _currentCursorVisibility = visibility;
        }

        return true;
    }

    public void Cleanup ()
    {
        if (_initialCursorVisibility.HasValue)
        {
            SetCursorVisibility (_initialCursorVisibility.Value);
        }

        //SetConsoleOutputWindow (out _);

        ConsoleMode = _originalConsoleMode;

        _outputHandle = CreateConsoleScreenBuffer (
                                                   DesiredAccess.GenericRead | DesiredAccess.GenericWrite,
                                                   ShareMode.FileShareRead | ShareMode.FileShareWrite,
                                                   nint.Zero,
                                                   1,
                                                   nint.Zero
                                                  );

        if (!SetConsoleActiveScreenBuffer (_outputHandle))
        {
            int err = Marshal.GetLastWin32Error ();
            Console.WriteLine ("Error: {0}", err);
        }

        //if (_screenBuffer != nint.Zero)
        //{
        //    CloseHandle (_screenBuffer);
        //}

        //_screenBuffer = nint.Zero;

        _inputReadyCancellationTokenSource?.Cancel ();
        _inputReadyCancellationTokenSource?.Dispose ();
        _inputReadyCancellationTokenSource = null;
    }

    internal Size GetConsoleBufferWindow (out Point position)
    {
        if (_outputHandle == nint.Zero)
        {
            position = Point.Empty;

            return Size.Empty;
        }

        var csbi = new CONSOLE_SCREEN_BUFFER_INFOEX ();
        csbi.cbSize = (uint)Marshal.SizeOf (csbi);

        if (!GetConsoleScreenBufferInfoEx (_outputHandle, ref csbi))
        {
            //throw new System.ComponentModel.Win32Exception (Marshal.GetLastWin32Error ());
            position = Point.Empty;

            return Size.Empty;
        }

        Size sz = new (
                       csbi.srWindow.Right - csbi.srWindow.Left + 1,
                       csbi.srWindow.Bottom - csbi.srWindow.Top + 1);
        position = new (csbi.srWindow.Left, csbi.srWindow.Top);

        return sz;
    }

    internal Size GetConsoleOutputWindow (out Point position)
    {
        var csbi = new CONSOLE_SCREEN_BUFFER_INFOEX ();
        csbi.cbSize = (uint)Marshal.SizeOf (csbi);

        if (!GetConsoleScreenBufferInfoEx (_outputHandle, ref csbi))
        {
            throw new Win32Exception (Marshal.GetLastWin32Error ());
        }

        Size sz = new (
                       csbi.srWindow.Right - csbi.srWindow.Left + 1,
                       csbi.srWindow.Bottom - csbi.srWindow.Top + 1);
        position = new (csbi.srWindow.Left, csbi.srWindow.Top);

        return sz;
    }

    //internal Size SetConsoleWindow (short cols, short rows)
    //{
    //    var csbi = new CONSOLE_SCREEN_BUFFER_INFOEX ();
    //    csbi.cbSize = (uint)Marshal.SizeOf (csbi);

    //    if (!GetConsoleScreenBufferInfoEx (_screenBuffer, ref csbi))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }

    //    Coord maxWinSize = GetLargestConsoleWindowSize (_screenBuffer);
    //    short newCols = Math.Min (cols, maxWinSize.X);
    //    short newRows = Math.Min (rows, maxWinSize.Y);
    //    csbi.dwSize = new Coord (newCols, Math.Max (newRows, (short)1));
    //    csbi.srWindow = new SmallRect (0, 0, newCols, newRows);
    //    csbi.dwMaximumWindowSize = new Coord (newCols, newRows);

    //    if (!SetConsoleScreenBufferInfoEx (_screenBuffer, ref csbi))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }

    //    var winRect = new SmallRect (0, 0, (short)(newCols - 1), (short)Math.Max (newRows - 1, 0));

    //    if (!SetConsoleWindowInfo (_outputHandle, true, ref winRect))
    //    {
    //        //throw new System.ComponentModel.Win32Exception (Marshal.GetLastWin32Error ());
    //        return new (cols, rows);
    //    }

    //    SetConsoleOutputWindow (csbi);

    //    return new (winRect.Right + 1, newRows - 1 < 0 ? 0 : winRect.Bottom + 1);
    //}

    //private void SetConsoleOutputWindow (CONSOLE_SCREEN_BUFFER_INFOEX csbi)
    //{
    //    if (_screenBuffer != nint.Zero && !SetConsoleScreenBufferInfoEx (_screenBuffer, ref csbi))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }
    //}

    //internal Size SetConsoleOutputWindow (out Point position)
    //{
    //    if (_screenBuffer == nint.Zero)
    //    {
    //        position = Point.Empty;

    //        return Size.Empty;
    //    }

    //    var csbi = new CONSOLE_SCREEN_BUFFER_INFOEX ();
    //    csbi.cbSize = (uint)Marshal.SizeOf (csbi);

    //    if (!GetConsoleScreenBufferInfoEx (_screenBuffer, ref csbi))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }

    //    Size sz = new (
    //                       csbi.srWindow.Right - csbi.srWindow.Left + 1,
    //                       Math.Max (csbi.srWindow.Bottom - csbi.srWindow.Top + 1, 0));
    //    position = new (csbi.srWindow.Left, csbi.srWindow.Top);
    //    SetConsoleOutputWindow (csbi);
    //    var winRect = new SmallRect (0, 0, (short)(sz.Width - 1), (short)Math.Max (sz.Height - 1, 0));

    //    if (!SetConsoleScreenBufferInfoEx (_outputHandle, ref csbi))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }

    //    if (!SetConsoleWindowInfo (_outputHandle, true, ref winRect))
    //    {
    //        throw new Win32Exception (Marshal.GetLastWin32Error ());
    //    }

    //    return sz;
    //}

    private uint ConsoleMode
    {
        get
        {
            GetConsoleMode (_inputHandle, out uint v);

            return v;
        }
        set => SetConsoleMode (_inputHandle, value);
    }

    [Flags]
    public enum ConsoleModes : uint
    {
        EnableProcessedInput = 1,
        EnableMouseInput = 16,
        EnableQuickEditMode = 64,
        EnableExtendedFlags = 128
    }

    [StructLayout (LayoutKind.Explicit, CharSet = CharSet.Unicode)]
    public struct KeyEventRecord
    {
        [FieldOffset (0)]
        [MarshalAs (UnmanagedType.Bool)]
        public bool bKeyDown;

        [FieldOffset (4)]
        [MarshalAs (UnmanagedType.U2)]
        public ushort wRepeatCount;

        [FieldOffset (6)]
        [MarshalAs (UnmanagedType.U2)]
        public ConsoleKeyMapping.VK wVirtualKeyCode;

        [FieldOffset (8)]
        [MarshalAs (UnmanagedType.U2)]
        public ushort wVirtualScanCode;

        [FieldOffset (10)]
        public char UnicodeChar;

        [FieldOffset (12)]
        [MarshalAs (UnmanagedType.U4)]
        public ControlKeyState dwControlKeyState;

        public readonly override string ToString ()
        {
            return
                $"[KeyEventRecord({(bKeyDown ? "down" : "up")},{wRepeatCount},{wVirtualKeyCode},{wVirtualScanCode},{new Rune (UnicodeChar).MakePrintable ()},{dwControlKeyState})]";
        }
    }

    [Flags]
    public enum ButtonState
    {
        NoButtonPressed = 0,
        Button1Pressed = 1,
        Button2Pressed = 4,
        Button3Pressed = 8,
        Button4Pressed = 16,
        RightmostButtonPressed = 2
    }

    [Flags]
    public enum ControlKeyState
    {
        NoControlKeyPressed = 0,
        RightAltPressed = 1,
        LeftAltPressed = 2,
        RightControlPressed = 4,
        LeftControlPressed = 8,
        ShiftPressed = 16,
        NumlockOn = 32,
        ScrolllockOn = 64,
        CapslockOn = 128,
        EnhancedKey = 256
    }

    [Flags]
    public enum EventFlags
    {
        NoEvent = 0,
        MouseMoved = 1,
        DoubleClick = 2,
        MouseWheeled = 4,
        MouseHorizontalWheeled = 8
    }

    [StructLayout (LayoutKind.Explicit)]
    public struct MouseEventRecord
    {
        [FieldOffset (0)]
        public Coord MousePosition;

        [FieldOffset (4)]
        public ButtonState ButtonState;

        [FieldOffset (8)]
        public ControlKeyState ControlKeyState;

        [FieldOffset (12)]
        public EventFlags EventFlags;

        public readonly override string ToString () { return $"[Mouse{MousePosition},{ButtonState},{ControlKeyState},{EventFlags}]"; }
    }

    public struct WindowBufferSizeRecord
    {
        public Coord _size;

        public WindowBufferSizeRecord (short x, short y) { _size = new Coord (x, y); }

        public readonly override string ToString () { return $"[WindowBufferSize{_size}"; }
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct MenuEventRecord
    {
        public uint dwCommandId;
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct FocusEventRecord
    {
        public uint bSetFocus;
    }

    public enum EventType : ushort
    {
        Focus = 0x10,
        Key = 0x1,
        Menu = 0x8,
        Mouse = 2,
        WindowBufferSize = 4
    }

    [StructLayout (LayoutKind.Explicit)]
    public struct InputRecord
    {
        [FieldOffset (0)]
        public EventType EventType;

        [FieldOffset (4)]
        public KeyEventRecord KeyEvent;

        [FieldOffset (4)]
        public MouseEventRecord MouseEvent;

        [FieldOffset (4)]
        public WindowBufferSizeRecord WindowBufferSizeEvent;

        [FieldOffset (4)]
        public MenuEventRecord MenuEvent;

        [FieldOffset (4)]
        public FocusEventRecord FocusEvent;

        public readonly override string ToString ()
        {
            return (EventType switch
                    {
                        EventType.Focus => FocusEvent.ToString (),
                        EventType.Key => KeyEvent.ToString (),
                        EventType.Menu => MenuEvent.ToString (),
                        EventType.Mouse => MouseEvent.ToString (),
                        EventType.WindowBufferSize => WindowBufferSizeEvent.ToString (),
                        _ => "Unknown event type: " + EventType
                    })!;
        }
    }

    [Flags]
    private enum ShareMode : uint
    {
        FileShareRead = 1,
        FileShareWrite = 2
    }

    [Flags]
    private enum DesiredAccess : uint
    {
        GenericRead = 2147483648,
        GenericWrite = 1073741824
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct ConsoleScreenBufferInfo
    {
        public Coord dwSize;
        public Coord dwCursorPosition;
        public ushort wAttributes;
        public SmallRect srWindow;
        public Coord dwMaximumWindowSize;
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct Coord
    {
        public short X;
        public short Y;

        public Coord (short x, short y)
        {
            X = x;
            Y = y;
        }

        public readonly override string ToString () { return $"({X},{Y})"; }
    }

    [StructLayout (LayoutKind.Explicit, CharSet = CharSet.Unicode)]
    public struct CharUnion
    {
        [FieldOffset (0)]
        public char UnicodeChar;

        [FieldOffset (0)]
        public byte AsciiChar;
    }

    [StructLayout (LayoutKind.Explicit, CharSet = CharSet.Unicode)]
    public struct CharInfo
    {
        [FieldOffset (0)]
        public CharUnion Char;

        [FieldOffset (2)]
        public ushort Attributes;
    }

    public struct ExtendedCharInfo
    {
        public char Char { get; set; }
        public Attribute Attribute { get; set; }
        public bool Empty { get; set; } // TODO: Temp hack until virtual terminal sequences

        public ExtendedCharInfo (char character, Attribute attribute)
        {
            Char = character;
            Attribute = attribute;
            Empty = false;
        }
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct SmallRect
    {
        public short Left;
        public short Top;
        public short Right;
        public short Bottom;

        public SmallRect (short left, short top, short right, short bottom)
        {
            Left = left;
            Top = top;
            Right = right;
            Bottom = bottom;
        }

        public static void MakeEmpty (ref SmallRect rect) { rect.Left = -1; }

        public static void Update (ref SmallRect rect, short col, short row)
        {
            if (rect.Left == -1)
            {
                rect.Left = rect.Right = col;
                rect.Bottom = rect.Top = row;

                return;
            }

            if (col >= rect.Left && col <= rect.Right && row >= rect.Top && row <= rect.Bottom)
            {
                return;
            }

            if (col < rect.Left)
            {
                rect.Left = col;
            }

            if (col > rect.Right)
            {
                rect.Right = col;
            }

            if (row < rect.Top)
            {
                rect.Top = row;
            }

            if (row > rect.Bottom)
            {
                rect.Bottom = row;
            }
        }

        public readonly override string ToString () { return $"Left={Left},Top={Top},Right={Right},Bottom={Bottom}"; }
    }

    [StructLayout (LayoutKind.Sequential)]
    public struct ConsoleKeyInfoEx
    {
        public ConsoleKeyInfo ConsoleKeyInfo;
        public bool CapsLock;
        public bool NumLock;
        public bool ScrollLock;

        public ConsoleKeyInfoEx (ConsoleKeyInfo consoleKeyInfo, bool capslock, bool numlock, bool scrolllock)
        {
            ConsoleKeyInfo = consoleKeyInfo;
            CapsLock = capslock;
            NumLock = numlock;
            ScrollLock = scrolllock;
        }

        /// <summary>
        ///     Prints a ConsoleKeyInfoEx structure
        /// </summary>
        /// <param name="ex"></param>
        /// <returns></returns>
        public readonly string ToString (ConsoleKeyInfoEx ex)
        {
            var ke = new Key ((KeyCode)ex.ConsoleKeyInfo.KeyChar);
            var sb = new StringBuilder ();
            sb.Append ($"Key: {(KeyCode)ex.ConsoleKeyInfo.Key} ({ex.ConsoleKeyInfo.Key})");
            sb.Append ((ex.ConsoleKeyInfo.Modifiers & ConsoleModifiers.Shift) != 0 ? " | Shift" : string.Empty);
            sb.Append ((ex.ConsoleKeyInfo.Modifiers & ConsoleModifiers.Control) != 0 ? " | Control" : string.Empty);
            sb.Append ((ex.ConsoleKeyInfo.Modifiers & ConsoleModifiers.Alt) != 0 ? " | Alt" : string.Empty);
            sb.Append ($", KeyChar: {ke.AsRune.MakePrintable ()} ({(uint)ex.ConsoleKeyInfo.KeyChar}) ");
            sb.Append (ex.CapsLock ? "caps," : string.Empty);
            sb.Append (ex.NumLock ? "num," : string.Empty);
            sb.Append (ex.ScrollLock ? "scroll," : string.Empty);
            string s = sb.ToString ().TrimEnd (',').TrimEnd (' ');

            return $"[ConsoleKeyInfoEx({s})]";
        }
    }

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern nint GetStdHandle (int nStdHandle);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool CloseHandle (nint handle);

    [DllImport ("kernel32.dll", SetLastError = true)]
    public static extern bool PeekConsoleInput (nint hConsoleInput, out InputRecord lpBuffer, uint nLength, out uint lpNumberOfEventsRead);

    [DllImport ("kernel32.dll", EntryPoint = "ReadConsoleInputW", CharSet = CharSet.Unicode)]
    public static extern bool ReadConsoleInput (
        nint hConsoleInput,
        out InputRecord lpBuffer,
        uint nLength,
        out uint lpNumberOfEventsRead
    );

    [DllImport ("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern bool ReadConsoleOutput (
        nint hConsoleOutput,
        [Out] CharInfo [] lpBuffer,
        Coord dwBufferSize,
        Coord dwBufferCoord,
        ref SmallRect lpReadRegion
    );

    // TODO: This API is obsolete. See https://learn.microsoft.com/en-us/windows/console/writeconsoleoutput
    [DllImport ("kernel32.dll", EntryPoint = "WriteConsoleOutputW", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern bool WriteConsoleOutput (
        nint hConsoleOutput,
        CharInfo [] lpBuffer,
        Coord dwBufferSize,
        Coord dwBufferCoord,
        ref SmallRect lpWriteRegion
    );

    [DllImport ("kernel32.dll", EntryPoint = "WriteConsole", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern bool WriteConsole (
        nint hConsoleOutput,
        string lpbufer,
        uint NumberOfCharsToWriten,
        out uint lpNumberOfCharsWritten,
        nint lpReserved
    );

    [DllImport ("kernel32.dll", SetLastError = true)]
    static extern bool FlushFileBuffers (nint hFile);

    [DllImport ("kernel32.dll")]
    private static extern bool SetConsoleCursorPosition (nint hConsoleOutput, Coord dwCursorPosition);

    [StructLayout (LayoutKind.Sequential)]
    public struct ConsoleCursorInfo
    {
        /// <summary>
        /// The percentage of the character cell that is filled by the cursor.This value is between 1 and 100.
        /// The cursor appearance varies, ranging from completely filling the cell to showing up as a horizontal
        /// line at the bottom of the cell.
        /// </summary>
        public uint dwSize;
        public bool bVisible;
    }

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool SetConsoleCursorInfo (nint hConsoleOutput, [In] ref ConsoleCursorInfo lpConsoleCursorInfo);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool GetConsoleCursorInfo (nint hConsoleOutput, out ConsoleCursorInfo lpConsoleCursorInfo);

    [DllImport ("kernel32.dll")]
    private static extern bool GetConsoleMode (nint hConsoleHandle, out uint lpMode);

    [DllImport ("kernel32.dll")]
    private static extern bool SetConsoleMode (nint hConsoleHandle, uint dwMode);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern nint CreateConsoleScreenBuffer (
        DesiredAccess dwDesiredAccess,
        ShareMode dwShareMode,
        nint secutiryAttributes,
        uint flags,
        nint screenBufferData
    );

    internal static nint INVALID_HANDLE_VALUE = new (-1);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool SetConsoleActiveScreenBuffer (nint handle);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool GetNumberOfConsoleInputEvents (nint handle, out uint lpcNumberOfEvents);

    internal uint GetNumberOfConsoleInputEvents ()
    {
        if (!GetNumberOfConsoleInputEvents (_inputHandle, out uint numOfEvents))
        {
            Console.WriteLine ($"Error: {Marshal.GetLastWin32Error ()}");

            return 0;
        }

        return numOfEvents;
    }

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool FlushConsoleInputBuffer (nint handle);

    internal void FlushConsoleInputBuffer ()
    {
        if (!FlushConsoleInputBuffer (_inputHandle))
        {
            Console.WriteLine ($"Error: {Marshal.GetLastWin32Error ()}");
        }
    }

    private int _retries;

#if false // Not needed on the constructor. Perhaps could be used on resizing. To study.
		[DllImport ("kernel32.dll", ExactSpelling = true)]
		static extern IntPtr GetConsoleWindow ();

		[DllImport ("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
		static extern bool ShowWindow (IntPtr hWnd, int nCmdShow);

		public const int HIDE = 0;
		public const int MAXIMIZE = 3;
		public const int MINIMIZE = 6;
		public const int RESTORE = 9;

		internal void ShowWindow (int state)
		{
			IntPtr thisConsole = GetConsoleWindow ();
			ShowWindow (thisConsole, state);
		}
#endif

    // See: https://github.com/gui-cs/Terminal.Gui/issues/357

    [StructLayout (LayoutKind.Sequential)]
    public struct CONSOLE_SCREEN_BUFFER_INFOEX
    {
        public uint cbSize;
        public Coord dwSize;
        public Coord dwCursorPosition;
        public ushort wAttributes;
        public SmallRect srWindow;
        public Coord dwMaximumWindowSize;
        public ushort wPopupAttributes;
        public bool bFullscreenSupported;

        [MarshalAs (UnmanagedType.ByValArray, SizeConst = 16)]
        public COLORREF [] ColorTable;
    }

    [StructLayout (LayoutKind.Explicit, Size = 4)]
    public struct COLORREF
    {
        public COLORREF (byte r, byte g, byte b)
        {
            Value = 0;
            R = r;
            G = g;
            B = b;
        }

        public COLORREF (uint value)
        {
            R = 0;
            G = 0;
            B = 0;
            Value = value & 0x00FFFFFF;
        }

        [FieldOffset (0)]
        public byte R;

        [FieldOffset (1)]
        public byte G;

        [FieldOffset (2)]
        public byte B;

        [FieldOffset (0)]
        public uint Value;
    }

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool GetConsoleScreenBufferInfoEx (nint hConsoleOutput, ref CONSOLE_SCREEN_BUFFER_INFOEX csbi);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool SetConsoleScreenBufferInfoEx (nint hConsoleOutput, ref CONSOLE_SCREEN_BUFFER_INFOEX consoleScreenBufferInfo);

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern bool SetConsoleWindowInfo (
        nint hConsoleOutput,
        bool bAbsolute,
        [In] ref SmallRect lpConsoleWindow
    );

    [DllImport ("kernel32.dll", SetLastError = true)]
    private static extern Coord GetLargestConsoleWindowSize (
        nint hConsoleOutput
    );
}