using System;
using System.Collections.Generic;
using System.IO.Ports;
using System.Linq;
using System.Timers;

public sealed class SerialPortWatcher : IDisposable
{
    private readonly System.Timers.Timer _timer;
    private HashSet<string> _last = new(StringComparer.OrdinalIgnoreCase);

    public event Action<string[]>? PortsAdded;
    public event Action<string[]>? PortsRemoved;

    public SerialPortWatcher(double intervalMs = 1000)
    {
        _timer = new System.Timers.Timer(intervalMs);
        _timer.Elapsed += (_, _) => Tick();
        _timer.AutoReset = true;
    }

    public void Start()
    {
        _last = GetPorts();
        _timer.Start();
    }

    public void Stop() => _timer.Stop();

    private void Tick()
    {
        var current = GetPorts();

        var added = current.Except(_last).ToArray();
        var removed = _last.Except(current).ToArray();

        if (added.Length > 0) PortsAdded?.Invoke(added);
        if (removed.Length > 0) PortsRemoved?.Invoke(removed);

        _last = current;
    }

    private static HashSet<string> GetPorts()
        => new HashSet<string>(SerialPort.GetPortNames(), StringComparer.OrdinalIgnoreCase);

    public void Dispose()
    {
        _timer.Stop();
        _timer.Dispose();
    }
}