Substation/MainForm.cs

using System.ComponentModel;
using System.Drawing.Drawing2D;
using NAudio.CoreAudioApi;

namespace Substation;

public class MainForm : Form
{
    readonly CoyoteDevice _device;
    readonly State          _state;
    readonly Server         _server;

    readonly NotifyIcon       _tray;
    readonly Label            _lblBle;
    readonly Label            _lblWs;
    readonly Label            _lblDeviceName;
    readonly TextBox          _txtDeviceName;
    readonly Button           _btnConnect;
    readonly Button           _btnStop;
    readonly System.Windows.Forms.Timer _statusTimer;
    readonly CancellationTokenSource _loopCts;

    readonly HeatMap _heatA;
    readonly HeatMap _heatB;
    readonly ProgressBar _gaugeRecvA;
    readonly ProgressBar _gaugeRecvB;
    readonly Label _lblSendA;
    readonly Label _lblSendB;
    readonly Label _lblRecvA;
    readonly Label _lblRecvB;
    readonly TrackBar _limitBarA;
    readonly TrackBar _limitBarB;
    readonly TrackBar _ampBarA;
    readonly TrackBar _ampBarB;
    readonly Label _lblLimitA;
    readonly Label _lblLimitB;
    readonly Label _lblLimitValA;
    readonly Label _lblLimitValB;
    readonly Label _lblAmpA;
    readonly Label _lblAmpB;
    readonly Label _lblAmpValA;
    readonly Label _lblAmpValB;
    readonly CheckBox _chkScaleA;
    readonly CheckBox _chkScaleB;
    readonly CheckBox _chkSwap;

    readonly Icon _iconNeutral;
    readonly Icon _iconActive;
    readonly Icon _iconHot;
    string _trayState = "";

    readonly Button _btnLive;
    readonly Button _btnPattern;
    readonly Button _btnRandom;
    readonly Label _lblTrack;
    readonly Label _lblAudioDev;
    readonly ComboBox _cboAudioDev;
    bool _isLiveRunning;
    bool _isPatternRunning;
    bool _isRandomRunning;
    LiveCapture? _liveCapture;

    public MainForm(CoyoteDevice device, State state, Server server)
    {
        _device = device;
        _state  = state;
        _server = server;
        _loopCts = new CancellationTokenSource();

        Text = $"Substation {typeof(MainForm).Assembly.GetName().Version}";
        ClientSize = new Size(420, 520);
        FormBorderStyle = FormBorderStyle.FixedSingle;
        MaximizeBox = false;
        StartPosition = FormStartPosition.CenterScreen;
        ShowInTaskbar = true;

        _lblBle = new Label
        {
            Text = "BLE: searching...",
            Location = new Point(16, 16),
            Size = new Size(388, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };

        _lblWs = new Label
        {
            Text = "WS: idle",
            Location = new Point(16, 40),
            Size = new Size(388, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };

        _lblDeviceName = new Label
        {
            Text = "Device:",
            Location = new Point(16, 66),
            Size = new Size(48, 20)
        };
        _txtDeviceName = new TextBox
        {
            Text = "47L121000",
            Location = new Point(68, 64),
            Size = new Size(160, 20)
        };

        _btnConnect = new Button
        {
            Text = "Connect",
            Location = new Point(236, 64),
            Size = new Size(80, 24)
        };
        _btnConnect.Click += OnConnect;

        _chkSwap = new CheckBox
        {
            Text = "Swap",
            Location = new Point(328, 66),
            Size = new Size(56, 20),
            Checked = false
        };
        _chkSwap.CheckedChanged += OnSwapChanged;

        _btnLive = new Button
        {
            Text = "Live",
            Location = new Point(16, 96),
            Size = new Size(80, 32)
        };
        _btnLive.Click += OnLive;

        _btnPattern = new Button
        {
            Text = "Pattern",
            Location = new Point(104, 96),
            Size = new Size(80, 32)
        };
        _btnPattern.Click += OnPattern;

        _btnRandom = new Button
        {
            Text = "Random",
            Location = new Point(192, 96),
            Size = new Size(80, 32)
        };
        _btnRandom.Click += OnRandom;

        _btnStop = new Button
        {
            Text = "Stop All",
            Location = new Point(324, 96),
            Size = new Size(80, 32)
        };
        _btnStop.Click += OnStop;

        _lblAudioDev = new Label
        {
            Text = "Audio:",
            Location = new Point(16, 134),
            Size = new Size(40, 20)
        };
        _cboAudioDev = new ComboBox
        {
            DropDownStyle = ComboBoxStyle.DropDownList,
            Location = new Point(60, 132),
            Size = new Size(344, 22)
        };
        PopulateAudioDevices();

        _lblTrack = new Label
        {
            Text = "",
            Location = new Point(16, 158),
            Size = new Size(388, 16),
            ForeColor = Color.DimGray
        };

        _lblSendA = new Label
        {
            Text = "Send A",
            Location = new Point(16, 184),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _heatA = new HeatMap(60)
        {
            Location = new Point(72, 182),
            Size = new Size(332, 22)
        };
        _lblSendB = new Label
        {
            Text = "Send B",
            Location = new Point(16, 212),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _heatB = new HeatMap(60)
        {
            Location = new Point(72, 210),
            Size = new Size(332, 22)
        };
        _lblRecvA = new Label
        {
            Text = "Recv A",
            Location = new Point(16, 240),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _gaugeRecvA = new ProgressBar
        {
            Location = new Point(72, 240),
            Size = new Size(332, 20),
            Minimum = 0,
            Maximum = 200,
            Style = ProgressBarStyle.Continuous
        };
        _lblRecvB = new Label
        {
            Text = "Recv B",
            Location = new Point(16, 266),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _gaugeRecvB = new ProgressBar
        {
            Location = new Point(72, 266),
            Size = new Size(332, 20),
            Minimum = 0,
            Maximum = 200,
            Style = ProgressBarStyle.Continuous
        };

        _lblLimitA = new Label
        {
            Text = "Lim A",
            Location = new Point(16, 298),
            Size = new Size(40, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _limitBarA = new TrackBar
        {
            Location = new Point(60, 294),
            Size = new Size(220, 45),
            Minimum = 0,
            Maximum = 200,
            TickFrequency = 50,
            Value = 30
        };
        _limitBarA.ValueChanged += OnLimitChanged;
        FixTrackbarKeys(_limitBarA);
        _lblLimitValA = new Label
        {
            Text = "30",
            Location = new Point(286, 298),
            Size = new Size(32, 20),
            TextAlign = ContentAlignment.MiddleRight
        };
        _chkScaleA = new CheckBox
        {
            Text = "Scale",
            Location = new Point(320, 298),
            Size = new Size(76, 24),
            Checked = false
        };
        _chkScaleA.CheckedChanged += OnLimitChanged;

        _lblLimitB = new Label
        {
            Text = "Lim B",
            Location = new Point(16, 346),
            Size = new Size(40, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _limitBarB = new TrackBar
        {
            Location = new Point(60, 342),
            Size = new Size(220, 45),
            Minimum = 0,
            Maximum = 200,
            TickFrequency = 50,
            Value = 30
        };
        _limitBarB.ValueChanged += OnLimitChanged;
        FixTrackbarKeys(_limitBarB);
        _lblLimitValB = new Label
        {
            Text = "30",
            Location = new Point(286, 346),
            Size = new Size(32, 20),
            TextAlign = ContentAlignment.MiddleRight
        };
        _chkScaleB = new CheckBox
        {
            Text = "Scale",
            Location = new Point(320, 346),
            Size = new Size(76, 24),
            Checked = false
        };
        _chkScaleB.CheckedChanged += OnLimitChanged;
        OnLimitChanged(null, EventArgs.Empty);

        _lblAmpA = new Label
        {
            Text = "Amp A",
            Location = new Point(16, 394),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _ampBarA = new TrackBar
        {
            Location = new Point(68, 390),
            Size = new Size(212, 45),
            Minimum = 0,
            Maximum = 100,
            TickFrequency = 25,
            Value = 0
        };
        _ampBarA.ValueChanged += OnAmpChanged;
        FixTrackbarKeys(_ampBarA);
        _lblAmpValA = new Label
        {
            Text = "0",
            Location = new Point(286, 394),
            Size = new Size(32, 20),
            TextAlign = ContentAlignment.MiddleRight
        };

        _lblAmpB = new Label
        {
            Text = "Amp B",
            Location = new Point(16, 442),
            Size = new Size(48, 20),
            Font = new Font(Font.FontFamily, 9, FontStyle.Bold)
        };
        _ampBarB = new TrackBar
        {
            Location = new Point(68, 438),
            Size = new Size(212, 45),
            Minimum = 0,
            Maximum = 100,
            TickFrequency = 25,
            Value = 0
        };
        _ampBarB.ValueChanged += OnAmpChanged;
        FixTrackbarKeys(_ampBarB);
        _lblAmpValB = new Label
        {
            Text = "0",
            Location = new Point(286, 442),
            Size = new Size(32, 20),
            TextAlign = ContentAlignment.MiddleRight
        };
        OnAmpChanged(null, EventArgs.Empty);

        Controls.AddRange(new Control[] { _lblBle, _lblWs, _lblDeviceName, _txtDeviceName, _btnConnect, _chkSwap, _btnLive, _btnPattern, _btnRandom, _btnStop, _lblAudioDev, _cboAudioDev, _lblTrack, _lblSendA, _heatA, _lblSendB, _heatB, _lblRecvA, _gaugeRecvA, _lblRecvB, _gaugeRecvB, _lblLimitA, _limitBarA, _lblLimitValA, _chkScaleA, _lblLimitB, _limitBarB, _lblLimitValB, _chkScaleB, _lblAmpA, _ampBarA, _lblAmpValA, _lblAmpB, _ampBarB, _lblAmpValB });

        // Tray icon — three cached variants: neutral=gray, active=gold, hot=red-orange
        _iconNeutral = CreateVoltageIcon(Color.Gray);
        _iconActive  = CreateVoltageIcon(Color.Gold);
        _iconHot     = CreateVoltageIcon(Color.OrangeRed);
        Icon = _iconActive;
        _tray = new NotifyIcon
        {
            Icon = _iconActive,
            Visible = true,
            Text = "Substation"
        };
        _tray.ContextMenuStrip = new ContextMenuStrip();
        _tray.ContextMenuStrip.Items.Add("Show", null, (_, _) => ShowFromTray());
        _tray.ContextMenuStrip.Items.Add("-");
        _tray.ContextMenuStrip.Items.Add("Exit", null, (_, _) => ExitFromTray());
        _tray.DoubleClick += (_, _) => ShowFromTray();

        _statusTimer = new System.Windows.Forms.Timer { Interval = 1000 };
        _statusTimer.Tick += OnStatusTick;
        _statusTimer.Start();

        Load += OnLoad;
        FormClosing += OnFormClosing;
        Resize += OnResize;

        _server.ClientChanged += OnWsClientChanged;
        _device.ConnectionChanged += OnDeviceConnectionChanged;
        _device.StrengthChanged += OnDeviceStrengthChanged;
    }

    async void OnLoad(object? sender, EventArgs e)
    {
        _ = _server.RunAsync(CancellationToken.None);
        _ = Task.Run(() => TickLoop(_loopCts.Token));
        try
        {
            await _device.ConnectAsync(_txtDeviceName.Text);
        }
        catch (Exception ex)
        {
            Console.Error.WriteLine($"[BLE] auto-connect failed: {ex.Message}");
        }
    }

    async Task TickLoop(CancellationToken ct)
    {
        while (!ct.IsCancellationRequested)
        {
            try
            {
                var (modeA, valA, modeB, valB, freqA, intA, freqB, intB) = _state.ConsumeTick();
                if (_device.IsConnected)
                {
                    var frame = B0.Build(0, modeA, modeB, valA, valB, freqA, intA, freqB, intB);
                    await _device.SendB0(frame);
                }
                if (!IsDisposed)
                {
                    BeginInvoke(() =>
                    {
                        double aScale = _state.LimitScaleA;
                        double bScale = _state.LimitScaleB;
                        var scaledIntA = new byte[4];
                        var scaledIntB = new byte[4];
                        for (int i = 0; i < 4; i++)
                        {
                            scaledIntA[i] = (byte)Math.Round(intA[i] * aScale);
                            scaledIntB[i] = (byte)Math.Round(intB[i] * bScale);
                        }
                        _heatA.AddTick(freqA, scaledIntA, _state.LastActiveA);
                        _heatB.AddTick(freqB, scaledIntB, _state.LastActiveB);
                    });
                }
            }
            catch (Exception ex)
            {
                Console.Error.WriteLine($"[tick] error: {ex.Message}");
            }
            try { await Task.Delay(100, ct); } catch (OperationCanceledException) { break; }
        }
    }

    void ShowFromTray()
    {
        Show();
        WindowState = FormWindowState.Normal;
        Activate();
    }

    void ExitFromTray()
    {
        _tray.Visible = false;
        Application.Exit();
    }

    void OnResize(object? sender, EventArgs e)
    {
        if (WindowState == FormWindowState.Minimized)
            Hide();
    }

    void OnFormClosing(object? sender, FormClosingEventArgs e)
    {
        _tray.Visible = false;
        _statusTimer.Stop();
        _loopCts.Cancel();
        _server.Stop();
    }

    void OnConnect(object? sender, EventArgs e)
    {
        if (_device.IsConnected) return;
        _btnConnect.Enabled = false;
        _lblBle.Text = "BLE: connecting...";
        Task.Run(async () =>
        {
            try
            {
                await _device.ConnectAsync(_txtDeviceName.Text);
            }
            catch (Exception ex)
            {
                BeginInvoke(() => _lblBle.Text = $"BLE: error - {ex.Message}");
            }
            finally
            {
                BeginInvoke(() => _btnConnect.Enabled = true);
            }
        });
    }

    void OnWsClientChanged(bool connected)
    {
        if (IsDisposed) return;
        BeginInvoke(() =>
        {
            _lblWs.Text = connected ? "WS: client connected" : "WS: idle";
            RefreshButtonStates();
            UpdateTrayIcon();
        });
    }

    void OnDeviceConnectionChanged(bool connected)
    {
        if (IsDisposed) return;
        BeginInvoke(() =>
        {
            _lblBle.Text = connected
                ? $"BLE: connected ({_device.DeviceName})"
                : "BLE: disconnected";
            _btnConnect.Enabled = !connected;
            RefreshButtonStates();
        });
    }

    void OnDeviceStrengthChanged(int a, int b)
    {
        if (IsDisposed) return;
        BeginInvoke(() =>
        {
            if (_state.SwapChannels) (a, b) = (b, a);
            _gaugeRecvA.Value = Math.Clamp(a, 0, 200);
            _gaugeRecvB.Value = Math.Clamp(b, 0, 200);
        });
    }

    void RefreshButtonStates()
    {
        bool busy = _isLiveRunning || _isPatternRunning || _isRandomRunning;
        _btnLive.Enabled = !_server.HasClient && !busy;
        _btnPattern.Enabled = !_server.HasClient && !busy;
        _btnRandom.Enabled = !_server.HasClient && !busy;
        _btnStop.Enabled = true;
    }

    void OnStatusTick(object? sender, EventArgs e)
    {
        if (IsDisposed) return;

        if (_isLiveRunning)
        {
            _lblTrack.Text = "Live capture";
        }
        else if (_isPatternRunning)
        {
            _lblTrack.Text = $"Pattern: {_patternName}";
        }
        else if (_isRandomRunning)
        {
            _lblTrack.Text = "Random noise";
        }

        UpdateTrayIcon();
    }

    void OnStop(object? sender, EventArgs e)
    {
        StopLive();
        StopPattern();
        StopRandom();
        _state.SetStrength('A', 0);
        _state.SetStrength('B', 0);
        _state.Stop('A');
        _state.Stop('B');
    }

    void OnLimitChanged(object? sender, EventArgs e)
    {
        var maxA = _limitBarA.Value;
        var maxB = _limitBarB.Value;
        var modeA = _chkScaleA.Checked ? LimitMode.Scale : LimitMode.Clamp;
        var modeB = _chkScaleB.Checked ? LimitMode.Scale : LimitMode.Clamp;
        _state.SetLimitA(maxA, modeA);
        _state.SetLimitB(maxB, modeB);
        _lblLimitValA.Text = $"{maxA}";
        _lblLimitValB.Text = $"{maxB}";
    }

    void OnAmpChanged(object? sender, EventArgs e)
    {
        var ampA = 1.0 + _ampBarA.Value / 100.0 * 9.0;
        var ampB = 1.0 + _ampBarB.Value / 100.0 * 9.0;
        _state.SetAmpA(ampA);
        _state.SetAmpB(ampB);
        _lblAmpValA.Text = $"{_ampBarA.Value}";
        _lblAmpValB.Text = $"{_ampBarB.Value}";
    }

    void OnSwapChanged(object? sender, EventArgs e)
    {
        _state.SwapChannels = _chkSwap.Checked;
    }

    void PopulateAudioDevices()
    {
        using var enumerator = new MMDeviceEnumerator();
        var defaultDev = enumerator.GetDefaultAudioEndpoint(DataFlow.Render, Role.Console);
        var devices = enumerator.EnumerateAudioEndPoints(DataFlow.Render, DeviceState.Active);

        _cboAudioDev.Items.Clear();
        int defaultIdx = 0;
        for (int i = 0; i < devices.Count; i++)
        {
            _cboAudioDev.Items.Add(devices[i]);
            if (devices[i].ID == defaultDev.ID)
                defaultIdx = i;
        }
        _cboAudioDev.SelectedIndex = defaultIdx;
    }

    void OnLive(object? sender, EventArgs e)
    {
        if (_isLiveRunning || _server.HasClient) return;
        if (_cboAudioDev.SelectedItem is not MMDevice dev) return;

        _isLiveRunning = true;
        _btnLive.Enabled = false;
        _lblTrack.Text = "Starting live capture...";

        _state.SetStrength('A', 60);
        _state.SetStrength('B', 60);
        _state.Stop('A');
        _state.Stop('B');

        _liveCapture = new LiveCapture(_state, dev);
        _liveCapture.Stopped += () => BeginInvoke(StopLive);
        _liveCapture.Start();

        _lblTrack.Text = "Live capture";
        RefreshButtonStates();
    }

    void StopLive()
    {
        if (_liveCapture != null)
        {
            try { _liveCapture.Stop(); } catch { }
            try { _liveCapture.Dispose(); } catch { }
            _liveCapture = null;
        }

        if (_isLiveRunning)
        {
            _isLiveRunning = false;
            if (!IsDisposed)
            {
                _lblTrack.Text = "";
                RefreshButtonStates();
            }
        }
    }

    string _patternName = "";
    CancellationTokenSource? _patternCts;

    void OnPattern(object? sender, EventArgs e)
    {
        if (_isPatternRunning || _server.HasClient) return;

        var url = ShowInputDialog("Paste xToys pattern URL:", "Pattern Import");
        if (string.IsNullOrWhiteSpace(url)) return;

        _isPatternRunning = true;
        _btnPattern.Enabled = false;
        _lblTrack.Text = "Loading pattern...";

        _patternCts = new CancellationTokenSource();
        Task.Run(() => RunPatternAsync(url, _patternCts.Token));
    }

    async Task RunPatternAsync(string url, CancellationToken ct)
    {
        XToysPattern? pattern = null;
        try
        {
            pattern = await XToysPatternImporter.ImportAsync(url);
        }
        catch (Exception ex)
        {
            BeginInvoke(() =>
            {
                _lblTrack.Text = $"Pattern failed: {ex.Message?.Split('\n')[0]}";
                _isPatternRunning = false;
                RefreshButtonStates();
            });
            return;
        }

        _patternName = pattern.Name;

        _state.SetStrength('A', 60);
        _state.SetStrength('B', 60);
        _state.Stop('A');
        _state.Stop('B');

        BeginInvoke(() => _lblTrack.Text = $"Pattern: {_patternName}");

        // Continuously enqueue pattern frames at 100ms per frame
        int idx = 0;
        while (!ct.IsCancellationRequested && _isPatternRunning)
        {
            var frameA = pattern.ChannelA[idx];
            var frameB = pattern.ChannelB[idx];
            _state.EnqueueStream('A', new[] { frameA });
            _state.EnqueueStream('B', new[] { frameB });
            idx = (idx + 1) % pattern.ChannelA.Count;

            try { await Task.Delay(100, ct); } catch (OperationCanceledException) { break; }
        }
    }

    void StopPattern()
    {
        _patternCts?.Cancel();
        _patternCts = null;

        if (_isPatternRunning)
        {
            _isPatternRunning = false;
            if (!IsDisposed)
            {
                _lblTrack.Text = "";
                RefreshButtonStates();
            }
        }
    }

    CancellationTokenSource? _randomCts;

    void OnRandom(object? sender, EventArgs e)
    {
        if (_isRandomRunning || _server.HasClient) return;

        _isRandomRunning = true;
        _btnRandom.Enabled = false;
        _lblTrack.Text = "Random noise";

        _state.SetStrength('A', 60);
        _state.SetStrength('B', 60);
        _state.Stop('A');
        _state.Stop('B');

        _randomCts = new CancellationTokenSource();
        Task.Run(() => RunRandomAsync(_randomCts.Token));
    }

    async Task RunRandomAsync(CancellationToken ct)
    {
        // Pink noise via Voss-McCartney algorithm (1/f spectrum)
        // Separate state per channel, B inverted for counterphase
        var rng = new Random();
        int octaves = 8;
        var rowsA = new double[octaves];
        var rowsB = new double[octaves];
        double pinkA = 0, pinkB = 0;

        while (!ct.IsCancellationRequested && _isRandomRunning)
        {
            // Channel A
            int updateA = rng.Next(octaves);
            rowsA[updateA] = rng.NextDouble() * 2 - 1;
            pinkA = 0;
            for (int i = 0; i < octaves; i++) pinkA += rowsA[i];
            pinkA /= octaves;

            // Channel B (independent state, inverted for counterphase)
            int updateB = rng.Next(octaves);
            rowsB[updateB] = rng.NextDouble() * 2 - 1;
            pinkB = 0;
            for (int i = 0; i < octaves; i++) pinkB += rowsB[i];
            pinkB /= octaves;
            pinkB = -pinkB; // counterphase

            // Map pink noise (-1..1) to intensity (0..80, capped for comfort)
            int intA = (int)Math.Clamp((pinkA + 1) * 40, 0, 80);
            int intB = (int)Math.Clamp((pinkB + 1) * 40, 0, 80);

            // Random frequency: map pink noise to period (10-1000ms)
            int freqMsA = (int)Math.Clamp((pinkA + 1) * 500, 10, 1000);
            int freqMsB = (int)Math.Clamp((pinkB + 1) * 500, 10, 1000);

            var frameA = new WaveFrame(
                Freq.Compress4(new[] { freqMsA, freqMsA, freqMsA, freqMsA }),
                Intensity.Clamp4(new[] { intA, intA, intA, intA }));
            var frameB = new WaveFrame(
                Freq.Compress4(new[] { freqMsB, freqMsB, freqMsB, freqMsB }),
                Intensity.Clamp4(new[] { intB, intB, intB, intB }));

            _state.EnqueueStream('A', new[] { frameA });
            _state.EnqueueStream('B', new[] { frameB });

            try { await Task.Delay(100, ct); } catch (OperationCanceledException) { break; }
        }
    }

    void StopRandom()
    {
        _randomCts?.Cancel();
        _randomCts = null;

        if (_isRandomRunning)
        {
            _isRandomRunning = false;
            if (!IsDisposed)
            {
                _lblTrack.Text = "";
                RefreshButtonStates();
            }
        }
    }

    string ShowInputDialog(string prompt, string title)
    {
        using var dlg = new Form
        {
            Text = title,
            FormBorderStyle = FormBorderStyle.FixedDialog,
            ClientSize = new Size(380, 100),
            StartPosition = FormStartPosition.CenterParent,
            MaximizeBox = false,
            MinimizeBox = false
        };
        var lbl = new Label { Text = prompt, Location = new Point(12, 12), Size = new Size(356, 20) };
        var txt = new TextBox { Location = new Point(12, 36), Size = new Size(356, 22) };
        var ok = new Button { Text = "OK", DialogResult = DialogResult.OK, Location = new Point(200, 66), Size = new Size(80, 24) };
        var cancel = new Button { Text = "Cancel", DialogResult = DialogResult.Cancel, Location = new Point(288, 66), Size = new Size(80, 24) };
        dlg.Controls.AddRange(new Control[] { lbl, txt, ok, cancel });
        dlg.AcceptButton = ok;
        dlg.CancelButton = cancel;
        return dlg.ShowDialog(this) == DialogResult.OK ? txt.Text.Trim() : "";
    }

    void UpdateTrayIcon()
    {
        var newState = _state.IsSignaling ? "hot"
                      : _server.HasClient  ? "active"
                      : "neutral";
        if (newState == _trayState) return;
        _trayState = newState;
        _tray.Icon = newState switch
        {
            "hot"    => _iconHot,
            "active" => _iconActive,
            _        => _iconNeutral
        };
    }

    static void FixTrackbarKeys(TrackBar tb)
    {
        tb.KeyDown += (s, e) =>
        {
            if (s is not TrackBar t) return;
            int step = e.KeyCode == Keys.Up || e.KeyCode == Keys.Down ? 1
                     : e.KeyCode == Keys.PageUp || e.KeyCode == Keys.PageDown ? 10
                     : 0;
            if (step == 0) return;
            if (e.KeyCode is Keys.Up or Keys.PageUp or Keys.Home)
                t.Value = Math.Min(t.Maximum, t.Value + (e.KeyCode == Keys.Home ? t.Maximum : step));
            else
                t.Value = Math.Max(t.Minimum, t.Value - (e.KeyCode == Keys.End ? t.Maximum : step));
            e.Handled = true;
        };
    }

    static Icon CreateVoltageIcon(Color boltColor)
    {
        const int sz = 32;
        using var bmp = new Bitmap(sz, sz);
        using var g = Graphics.FromImage(bmp);
        g.SmoothingMode = SmoothingMode.AntiAlias;

        // Dark panel background with rounded corners.
        using var bg = new SolidBrush(Color.FromArgb(45, 45, 48));
        using var path = new GraphicsPath();
        int r = 6, pad = 1;
        var rect = new Rectangle(pad, pad, sz - 2 * pad, sz - 2 * pad);
        path.AddArc(rect.X, rect.Y, r, r, 180, 90);
        path.AddArc(rect.Right - r, rect.Y, r, r, 270, 90);
        path.AddArc(rect.Right - r, rect.Bottom - r, r, r, 0, 90);
        path.AddArc(rect.X, rect.Bottom - r, r, r, 90, 90);
        path.CloseFigure();
        g.FillPath(bg, path);

        // Generic voltage symbol: a bold lightning bolt in the given colour.
        var pts = new Point[]
        {
            new(21, 4),  new(10, 18), new(16, 18),
            new(13, 28), new(24, 13), new(17, 13)
        };
        using var bolt = new SolidBrush(boltColor);
        g.FillPolygon(bolt, pts);

        return Icon.FromHandle(bmp.GetHicon());
    }
}