using System.Diagnostics;
using System.IO.Ports;
using VRio.Core.Device;

namespace VRio.App;

/// <summary>
/// vRIO main window: the interactive cockpit panel on the left (the same
/// functional map RIOJoy's profile editor shows) and a control strip on the
/// right — COM port, device settings, and a live wire log. Open the COM port,
/// point RIOJoy at the other end of the null-modem pair, and every click here
/// arrives at RIOJoy exactly as if the physical cockpit sent it.
/// </summary>
internal sealed class MainForm : Form
{
    private readonly VRioDevice _device = new();
    private readonly VRioSerialService _service;
    private readonly PanelCanvas _canvas = new();

    private readonly ComboBox _portBox = new()
    {
        Location = new Point(80, 12),
        Width = 128,
        DropDownStyle = ComboBoxStyle.DropDownList,
    };
    private readonly Button _rescan = new() { Text = "Rescan", Location = new Point(214, 11), Width = 52 };
    private readonly Button _openClose = new() { Text = "Open", Location = new Point(272, 11), Width = 46 };
    private readonly Label _linkStatus = new()
    {
        Text = "Port closed.",
        Location = new Point(12, 42),
        AutoSize = true,
        ForeColor = Color.Gray,
    };

    private readonly NumericUpDown _verMajor = new() { Location = new Point(80, 24), Width = 44, Minimum = 0, Maximum = 127, Value = 4 };
    private readonly NumericUpDown _verMinor = new() { Location = new Point(140, 24), Width = 44, Minimum = 0, Maximum = 127, Value = 2 };
    private readonly CheckBox _spring = new() { Text = "Stick springs back to center", Location = new Point(10, 56), AutoSize = true, Checked = true };
    private readonly Button _centerAxes = new() { Text = "Center all axes", Location = new Point(10, 82), Width = 140, Height = 26 };
    private readonly Button _lampsOff = new() { Text = "All lamps off", Location = new Point(156, 82), Width = 140, Height = 26 };
    private readonly Button _testEnter = new() { Text = "Enter test mode", Location = new Point(10, 114), Width = 140, Height = 26 };
    private readonly Button _testExit = new() { Text = "Exit test mode", Location = new Point(156, 114), Width = 140, Height = 26 };
    private readonly CheckBox _wedgeBug = new()
    {
        Text = "Emulate the v4.2 reply-wedge bug",
        Location = new Point(10, 148),
        AutoSize = true,
    };
    private readonly Button _wedgeNow = new() { Text = "Wedge analog now", Location = new Point(10, 172), Width = 140, Height = 26 };

    private readonly Label _counters = new()
    {
        Location = new Point(12, 290),
        AutoSize = true,
        Font = new Font("Consolas", 8f),
    };

    private readonly Label _help = new()
    {
        Location = new Point(12, 348),
        MaximumSize = new Size(306, 0),
        AutoSize = true,
        ForeColor = Color.Gray,
        Text = "Left-click a cell: momentary press.  Right-click: latch it down.  " +
               "Drag the X/Y box and the Z / L / R gauges to move the axes.",
    };

    private readonly TextBox _logBox = new()
    {
        Location = new Point(12, 428),
        Multiline = true,
        ReadOnly = true,
        ScrollBars = ScrollBars.Vertical,
        BackColor = Color.FromArgb(24, 24, 24),
        ForeColor = Color.Gainsboro,
        Font = new Font("Consolas", 8f),
        Anchor = AnchorStyles.Top | AnchorStyles.Bottom | AnchorStyles.Left,
        WordWrap = false,
    };
    private readonly Button _clearLog = new()
    {
        Text = "Clear log",
        Width = 80,
        Anchor = AnchorStyles.Bottom | AnchorStyles.Left,
    };

    private readonly System.Windows.Forms.Timer _uiTimer = new() { Interval = 500 };
    private readonly Stopwatch _clock = Stopwatch.StartNew();

    public MainForm()
    {
        Text = "vRIO — Virtual RIO cockpit device";
        // Fit the window to its content: the cockpit canvas plus the 330px
        // control strip, with just enough height for the strip's log area.
        ClientSize = new Size(_canvas.Width + 332, Math.Max(_canvas.Height, 640));
        MinimumSize = new Size(1000, 620);
        StartPosition = FormStartPosition.CenterScreen;

        _service = new VRioSerialService(_device);

        // Panel canvas, scrolled if the window is smaller than the grid.
        var scroller = new Panel { Dock = DockStyle.Fill, AutoScroll = true, BackColor = Color.FromArgb(28, 28, 28) };
        scroller.Controls.Add(_canvas);

        Controls.Add(scroller);
        Controls.Add(BuildControlStrip());

        // Canvas ↔ device wiring.
        _canvas.LampProvider = _device.GetLamp;
        _canvas.AxisProvider = _device.GetAxis;
        _canvas.AddressPressed += _device.PressAddress;
        _canvas.AddressReleased += _device.ReleaseAddress;
        _canvas.AxisMoved += (axis, value) => _device.SetAxis(axis, value);

        // Device / service events arrive on worker threads; marshal to the UI.
        _device.LampChanged += (_, _) => RunOnUi(_canvas.Invalidate);
        _device.AxesChanged += () => RunOnUi(_canvas.Invalidate);
        _device.Logged += line => RunOnUi(() => PrependLog(line));
        _service.Logged += line => RunOnUi(() => PrependLog(line));
        _service.ConnectionChanged += open => RunOnUi(() => OnConnectionChanged(open));
        _service.HostHandshake += high => RunOnUi(() =>
            PrependLog(high ? "Host raised DTR (board-reset handshake)" : "Host dropped DTR"));

        _rescan.Click += (_, _) => RefreshPorts();
        _openClose.Click += (_, _) => ToggleOpen();
        _verMajor.ValueChanged += (_, _) => _device.VersionMajor = (byte)_verMajor.Value;
        _verMinor.ValueChanged += (_, _) => _device.VersionMinor = (byte)_verMinor.Value;
        _spring.CheckedChanged += (_, _) => _canvas.StickSpringsBack = _spring.Checked;
        _centerAxes.Click += (_, _) =>
        {
            foreach (RioAxis axis in (RioAxis[])Enum.GetValues(typeof(RioAxis)))
                _device.SetAxis(axis, 0);
        };
        _lampsOff.Click += (_, _) =>
        {
            _device.ClearLamps();
            _canvas.Invalidate();
        };
        _testEnter.Click += (_, _) => _device.SendTestMode(1);
        _testExit.Click += (_, _) => _device.SendTestMode(0);
        _wedgeBug.CheckedChanged += (_, _) => _device.EmulateReplyWedge = _wedgeBug.Checked;
        _wedgeNow.Click += (_, _) =>
        {
            _device.WedgeAnalogNow();
            UpdateStatus();
        };
        _clearLog.Click += (_, _) => _logBox.Clear();

        _uiTimer.Tick += (_, _) => UpdateStatus();
        _uiTimer.Start();

        FormClosed += (_, _) =>
        {
            _uiTimer.Dispose();
            _service.Dispose();
        };

        RefreshPorts();
        UpdateStatus();
        PrependLog("vRIO ready. Open a COM port, then point RIOJoy at the other end of the pair.");
    }

    private Panel BuildControlStrip()
    {
        var panel = new Panel
        {
            Dock = DockStyle.Right,
            Width = 330,
            // Height must be set before the anchored children are added:
            // Anchor offsets are captured against the parent's current size,
            // and the 100px default would pin the log box's bottom far below
            // the panel, making it grow past the window instead of scrolling.
            Height = ClientSize.Height,
            Padding = new Padding(8),
            BorderStyle = BorderStyle.FixedSingle,
        };

        panel.Controls.Add(new Label { Text = "COM port:", Location = new Point(12, 15), AutoSize = true });
        panel.Controls.Add(_portBox);
        panel.Controls.Add(_rescan);
        panel.Controls.Add(_openClose);
        panel.Controls.Add(_linkStatus);

        var device = new GroupBox { Text = "Device", Location = new Point(12, 68), Size = new Size(306, 210) };
        device.Controls.Add(new Label { Text = "Firmware:", Location = new Point(10, 27), AutoSize = true });
        device.Controls.Add(_verMajor);
        device.Controls.Add(new Label { Text = ".", Location = new Point(127, 27), AutoSize = true });
        device.Controls.Add(_verMinor);
        device.Controls.AddRange(new Control[] { _spring, _centerAxes, _lampsOff, _testEnter, _testExit, _wedgeBug, _wedgeNow });
        panel.Controls.Add(device);

        panel.Controls.Add(_counters);
        panel.Controls.Add(_help);
        panel.Controls.Add(new Label { Text = "Wire log:", Location = new Point(12, 410), AutoSize = true });

        _logBox.Size = new Size(306, ClientSize.Height - _logBox.Top - 44);
        panel.Controls.Add(_logBox);

        _clearLog.Location = new Point(12, ClientSize.Height - 36);
        panel.Controls.Add(_clearLog);

        return panel;
    }

    // ---- Port handling -----------------------------------------------------

    private void RefreshPorts()
    {
        string? current = _portBox.SelectedItem?.ToString();
        _portBox.Items.Clear();
        foreach (string name in SerialPort.GetPortNames().Distinct().OrderBy(n => n, StringComparer.OrdinalIgnoreCase))
            _portBox.Items.Add(name);

        if (_portBox.Items.Count == 0)
            return;
        int idx = current is null ? -1 : _portBox.Items.IndexOf(current);
        _portBox.SelectedIndex = idx >= 0 ? idx : 0;
    }

    private void ToggleOpen()
    {
        if (_service.IsOpen)
        {
            _service.Close();
            return;
        }

        if (_portBox.SelectedItem?.ToString() is not { } port)
        {
            MessageBox.Show(this, "No COM port selected. On a single PC, install a com0com virtual " +
                "null-modem pair and open one end here.", "vRIO", MessageBoxButtons.OK, MessageBoxIcon.Information);
            return;
        }

        try
        {
            _service.Open(port);
        }
        catch (Exception ex)
        {
            MessageBox.Show(this, $"Could not open {port}:\n{ex.Message}", "vRIO",
                MessageBoxButtons.OK, MessageBoxIcon.Warning);
        }
    }

    private void OnConnectionChanged(bool open)
    {
        _openClose.Text = open ? "Close" : "Open";
        _portBox.Enabled = _rescan.Enabled = !open;
        _linkStatus.Text = open ? $"Serving {_service.PortName} @ 9600 8N1." : "Port closed.";
        _linkStatus.ForeColor = open ? Color.ForestGreen : Color.Gray;
        UpdateStatus();
    }

    // ---- Status / log ------------------------------------------------------

    private void UpdateStatus()
    {
        long polls = _device.AnalogRequests;
        long dropped = _device.AnalogDropped;
        long bad = _device.BadChecksums;
        bool wedged = _device.AnalogWedged;
        _counters.Text = $"Analog polls served:  {polls}\n" +
                         $"Analog polls dropped: {dropped}\n" +
                         $"Bad checksums:        {bad}";

        _canvas.StatusText = _service.IsOpen
            ? $"vRIO {_device.VersionMajor}.{_device.VersionMinor} on {_service.PortName}\n" +
              (wedged
                  ? "** ANALOG WEDGED (v4.2 bug) — awaiting host reset **"
                  : $"{polls} analog polls" + (polls > 0 ? "  (host is alive)" : "  (no host traffic yet)"))
            : "PORT CLOSED\nOpen a COM port to go live.";
    }

    private void PrependLog(string line)
    {
        // Newest entry on top; older lines flow downward and eventually fall
        // off the bounded end, so the visible top is always current.
        string text = $"[{_clock.Elapsed.TotalSeconds,8:F2}s] {line}{Environment.NewLine}" + _logBox.Text;

        // Bound the log so an all-day session doesn't grow without limit;
        // cut at a line boundary so the tail isn't half an entry.
        if (text.Length > 120_000)
        {
            int cut = text.LastIndexOf(Environment.NewLine, 60_000, StringComparison.Ordinal);
            text = text.Substring(0, cut < 0 ? 60_000 : cut + Environment.NewLine.Length);
        }

        _logBox.Text = text;
        _logBox.SelectionStart = 0;
        _logBox.ScrollToCaret();
    }

    private void RunOnUi(Action action)
    {
        if (IsDisposed)
            return;
        if (InvokeRequired)
        {
            try { BeginInvoke(action); }
            catch (ObjectDisposedException) { }
            catch (InvalidOperationException) { } // handle not created / closing
            return;
        }
        action();
    }
}