barcode-host/Shared/KeyboardMouse/InputReader.cs

using Microsoft.Extensions.Logging;

namespace Barcode.Host.Shared.KeyboardMouse;

public class InputReader : IDisposable
{

    private long _Ticks;
    private bool _Disposing;
    private readonly int _PiOffset;
    private const int _BufferLength = 24;
    private readonly FileStream? _FileStream;
    private readonly ILogger<IDisposable> _Logger;
    private readonly byte[] _Buffer = new byte[_BufferLength];

    public string Path { get; init; }
    public bool Faulted { get; private set; }

    public event RaiseKeyPress? OnKeyPress;
    public event RaiseMouseMove? OnMouseMove;

    public delegate void RaiseKeyPress(KeyPressEvent e);
    public delegate void RaiseMouseMove(MouseMoveEvent e);

    public InputReader(string path, ILogger<IDisposable> logger)
    {
        Path = path;
        _Logger = logger;
        if (RunningOnRaspberryPi())
            _PiOffset = -8;
        try
        { _FileStream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite); }
        catch (UnauthorizedAccessException ex)
        {
            logger.LogError(ex, "Current user doesn't have permissions to access input data. Add user to input group to correct this error");
            Faulted = true;
        }
        catch (IOException ex)
        {
            logger.LogWarning(ex, $"Error occurred while trying to build stream for {path}");
            Faulted = true;
        }
        _ = Task.Run(Run);
    }

    private void Run()
    {
        while (true)
        {
            if (_Disposing)
                break;
            try
            {
                if (!Faulted && _FileStream is not null)
                    _ = _FileStream.Read(_Buffer, 0, _BufferLength);
            }
            catch (IOException ex)
            {
                _Logger.LogInformation(ex, $"Error occured while trying to read from the stream for {Path}");
                Faulted = true;
            }
            EventType type = GetEventType();
            switch (type)
            {
                case EventType.EV_SYN:
                    _Ticks = DateTime.Now.Ticks;
                    break;
                case EventType.EV_KEY:
                    HandleKeyPressEvent();
                    break;
                case EventType.EV_REL:
                    HandleMouseMoveEvent();
                    break;
            }
        }
    }

    private int GetValue()
    {
        byte[] valueBits = new[]
        {
            _Buffer[20 + _PiOffset],
            _Buffer[21 + _PiOffset],
            _Buffer[22 + _PiOffset],
            _Buffer[23 + _PiOffset]
        };
        int value = BitConverter.ToInt32(valueBits, 0);
        return value;
    }

    private short GetCode()
    {
        byte[] codeBits = new[]
        {
            _Buffer[18 + _PiOffset],
            _Buffer[19 + _PiOffset]
        };
        short code = BitConverter.ToInt16(codeBits, 0);
        return code;
    }

    private EventType GetEventType()
    {
        byte[] typeBits = new[]
        {
            _Buffer[16 + _PiOffset],
            _Buffer[17 + _PiOffset]
        };
        short type = BitConverter.ToInt16(typeBits, 0);
        EventType eventType = (EventType)type;
        return eventType;
    }

    private void HandleKeyPressEvent()
    {
        short code = GetCode();
        int value = GetValue();
        DateTime dateTime = DateTime.Now;
        KeyState keyState = (KeyState)value;
        EventCode eventCode = (EventCode)code;
        KeyPressEvent keyPressEvent = new(dateTime, eventCode, keyState, new TimeSpan(dateTime.Ticks - _Ticks));
        OnKeyPress?.Invoke(keyPressEvent);
    }

    private void HandleMouseMoveEvent()
    {
        short code = GetCode();
        int value = GetValue();
        MouseAxis axis = (MouseAxis)code;
        MouseMoveEvent e = new(axis, value);
        OnMouseMove?.Invoke(e);
    }

    public void Dispose()
    {
        _Disposing = true;
        _FileStream?.Dispose();
        GC.SuppressFinalize(this);
    }

    private static bool RunningOnRaspberryPi()
    {
        string path = "/proc/cpuinfo";
        string[] text = File.ReadAllLines(path);
        bool runningOnPi = text.Any(l => l.Contains("Raspberry Pi"));
        return runningOnPi;
    }

}