Nonemm/src/Nonemm.App/AppSession.cs

using Avalonia.Threading;
using Nonemm.App.Configuration;
using Nonemm.Contests;
using Nonemm.Core;
using Nonemm.Core.Calls;
using Nonemm.Core.Country;
using Nonemm.Digital;
using Nonemm.Keying;
using Nonemm.Network;
using Nonemm.Rig;
using Nonemm.Session;
using Nonemm.Spotting;
using Nonemm.Storage;

namespace Nonemm.App;

/// Everything the running program owns: the log store, the contest in progress,
/// the bandmap, the radio and the cluster. The windows read from this and one
/// `Changed` event tells them all to redraw.
public sealed class AppSession : IDisposable
{
    /// How often this station tells the others how it is doing. N1MM sends its
    /// status on the same sort of interval; every second would read the log
    /// sixty times a minute for two numbers that barely move.
    private static readonly TimeSpan StatusInterval = TimeSpan.FromSeconds(5);

    private LogStore? store;
    private readonly List<RigctldRadio> radios = [];
    private readonly List<OperatingPosition> positions = [];
    private int activeRadio;
    private ClusterClient? cluster;
    private StationNetwork? network;
    private StationLink? link;

    /// What was last said to the other stations about where this one is, so it
    /// is said again only when it changes.
    private (Frequency Where, string Mode, bool Running, int Radio) announced;
    /// When the last `STATUS` went out. It is not sent every second: it carries
    /// the rates, which are read out of the log.
    private DateTime statusSent;
    private DispatcherTimer? announcing;
    private MessageSender? keyer;
    private AlternatingCq? alternating;
    private MmttyEngine? digital;
    private DigitalEngineSender? digitalSender;
    private So2rBox? box;

    /// Which cluster spots reach the bandmap. Rebuilt whenever the settings or
    /// the support files change.
    private SpotFilter spotFilter = new();

    private readonly Random jitter = new();

    /// Spots wait here until the next flush. N1MM collects them the same way,
    /// because a skimmer feed sends more spots a minute than any window can
    /// usefully redraw.
    private readonly List<Spot> arriving = [];
    private readonly Lock arrivingGuard = new();
    private readonly Timer spotFlush;

    public AppSession(UserPaths paths, Settings settings)
    {
        Paths = paths;
        Settings = settings;
        paths.CreateFolders();
        Countries = LoadCountryFile(paths.CountryFile);
        Calls = LoadCallDatabase(paths.CallDatabaseFile);
        History = LoadCallHistory(settings.CallHistoryFile);
        Registry = ContestRegistry.FromFolder(
            paths.UserDefinedContests,
            out IReadOnlyList<string> problems,
            paths.SupportFiles);
        UserDefinedContestProblems = problems;
        BandPlan = settings.ToBandPlan();
        ApplySpotSettings();
        spotFlush = new Timer(_ => FlushSpots(), null, SpotFlushInterval, SpotFlushInterval);
    }

    /// How often the spots that have arrived go onto the bandmap. N1MM's own
    /// queue is flushed once a second.
    private static readonly TimeSpan SpotFlushInterval = TimeSpan.FromSeconds(1);

    public UserPaths Paths { get; }

    public Settings Settings { get; private set; }

    public ContestRegistry Registry { get; private set; }

    /// Where the bandmap paints the CW, digital and phone parts of a band.
    public BandPlan BandPlan { get; private set; }

    public IReadOnlyList<string> UserDefinedContestProblems { get; }

    public CountryFile? Countries { get; private set; }

    public CallDatabase Calls { get; private set; }

    /// What was published about the stations in this contest. Empty when no
    /// file is chosen, and then nothing is filled in for the operator.
    public CallHistory History { get; private set; } = CallHistory.Empty;

    public Bandmap Bandmap { get; } = new();

    /// Where the operator was last on each band and mode, for the band buttons.
    public BandMemory BandMemory { get; } = new();

    /// The contest in progress: one log and one score, however many radios.
    public ContestSession? Logging { get; private set; }

    /// The radio the operator is not on, or null at a one-radio station. The
    /// message macros that pass a station to the other band need it.
    public OperatingPosition? Other(OperatingPosition position) =>
        positions.FirstOrDefault(p => p.RadioNumber != position.RadioNumber);

    /// One per radio, in radio-number order. There is always at least one, so
    /// the program works with no radio connected.
    public IReadOnlyList<OperatingPosition> Positions => positions;

    /// The radio the operator is on.
    public OperatingPosition? Position =>
        activeRadio < positions.Count ? positions[activeRadio] : null;

    public CheckWindowSources? Check { get; private set; }

    /// Where a line of received text goes while the QTC window is taking
    /// traffic down on RTTY. The other station sends the header and the whole
    /// series in one transmission, and the operator clicks each line in the
    /// digital window rather than typing it, which is how N1MM works. The QTC
    /// window sets this while it is open and returns whether the line went
    /// into it.
    public Func<string, bool>? QtcLines { get; set; }

    /// What is spotted and not worked yet.
    public AvailableStations? Available { get; private set; }

    /// One entry per configured radio, in radio-number order.
    public IReadOnlyList<Radio> Radios => radios;

    /// The radio the operator is on. Null when none is configured, and then
    /// frequency and mode stay wherever they were last typed.
    public Radio? Radio => activeRadio < radios.Count ? radios[activeRadio] : null;

    public int ActiveRadioNumber => Position?.RadioNumber ?? 1;

    public ClusterClient? Cluster => cluster;

    public StationNetwork? Network => network;

    /// The link to the other logging computers, or null when the operator has
    /// not turned it on. The network status window reads it.
    public StationLink? Link => link;

    public MessageSender? Keyer => keyer;

    /// The digital modem, started by the digital window rather than at startup:
    /// it runs an engine under Wine, which is not something to do to an
    /// operator who is working CW.
    public MmttyEngine? Digital => digital;

    /// The same engine as something a macro can be sent through.
    public DigitalEngineSender? DigitalKeyer => digitalSender;

    /// Alternating CQ, or null while there is no keyer. It needs two radios to
    /// do anything, and a keyer that reports when a message has gone out.
    public AlternatingCq? Alternating => alternating;

    /// The SO2R box, or null when there is none and the operator switches the
    /// transmitter and the headphones by hand.
    public So2rBox? Box => box;

    /// True while both radios are in the headphones.
    public bool IsListeningToBoth { get; private set; }

    public event EventHandler? Changed;

    public event EventHandler? ContestChanged;

    public void Save(Settings settings)
    {
        Settings = settings;
        BandPlan = settings.ToBandPlan();
        ApplySpotSettings();
        settings.Save(Paths.SettingsFile);
        Changed?.Invoke(this, EventArgs.Empty);
    }

    public void OpenDatabase(string path)
    {
        bool sameFile = string.Equals(Settings.DatabasePath, path, StringComparison.Ordinal);
        store?.Dispose();
        store = SqliteLogStore.Open(path);
        Logging = null;
        Check = null;
        Available = null;
        Save(Settings with
        {
            DatabasePath = path,
            ContestNumber = sameFile ? Settings.ContestNumber : 0,
        });
        ContestChanged?.Invoke(this, EventArgs.Empty);
    }

    public LogStore Store =>
        store ?? throw new InvalidOperationException("no log database is open");

    public ContestInstance StartContest(ContestInstance instance)
    {
        ContestInstance stored = Store.AddContest(instance);
        OpenContest(stored.ContestNumber);
        return stored;
    }

    /// N1MM reads the `Contest` table when it opens a log, so the definition is
    /// written again whenever a contest is opened, not only when it is created.
    private void SaveDefinition(Contest contest) =>
        Store.SaveContestDefinition(ContestDefinitions.For(contest));

    public void OpenContest(int contestNumber)
    {
        ContestInstance instance = Store.Contest(contestNumber)
            ?? throw new InvalidOperationException($"no contest numbered {contestNumber} in the log");
        Contest contest = Registry.Create(instance.ContestName, ModeCategoryOf(instance));
        SaveDefinition(contest);
        Logging = new ContestSession(
            Store, contest, instance, Settings.Station.ToStationInfo(), Countries, History)
        {
            // whoever was at the radio when the last contest was open is still
            // there, and every contact he logs carries his callsign
            Operator = Settings.CurrentOperator,
            // N1MM stamps every contact with the computer that made it and the
            // station number of that computer, and a resync asks for the
            // contacts of one computer by name
            StationName = ComputerName,
            StationNumber = Settings.StationNumber,
        };
        positions.Clear();
        for (int number = 1; number <= PositionCount; number++)
        {
            positions.Add(new OperatingPosition(Logging, number));
        }
        activeRadio = Math.Min(activeRadio, positions.Count - 1);
        // the other stations refuse to resynchronise with a station on another
        // contest, and say so, which is only any use if they are told
        _ = link?.SendContestNameAsync();
        // and the highest serial number taken on each band, so a station that
        // joins a contest already under way starts where the others are. N1MM
        // sends the same message at the same point
        _ = link?.SendSerialNumbersAsync(Logging.Numbers.Snapshot());
        Logging.Changed += (_, _) => Changed?.Invoke(this, EventArgs.Empty);
        Logging.Logged += (_, qso) =>
        {
            // a WAE QTC row is traffic about a station, not a station on the air
            if (contest.IsContact(qso))
            {
                Bandmap.Add(new Spot(qso.Call, qso.Frequency, qso.TimestampUtc, SpotSource.Log));
            }
        };
        Logging.Logged += (_, qso) => _ = network?.SendAsync(qso, Settings.Station.Callsign);
        Logging.Edited += (_, change) => _ = network?.SendEditAsync(
            change.Qso, Settings.Station.Callsign, change.OldCall, change.OldTimestampUtc);
        Logging.Deleted += (_, qso) => _ = network?.SendDeleteAsync(qso, Settings.Station.Callsign);
        // and the same three to the other logging computers, which is a
        // different protocol on a different port
        Logging.Logged += (_, qso) => _ = link?.SendLoggedAsync(qso);
        // the number is announced when it is taken rather than when the contact
        // is logged, which is what keeps two operators off the same number
        Logging.Numbers.Reserved += (_, taken) =>
            _ = link?.SendReservedNumberAsync(taken.Number, SomewhereOn(taken.Band));
        Logging.Edited += (_, change) =>
            _ = link?.SendEditedAsync(change.Qso, change.OldCall, change.OldTimestampUtc);
        Logging.Deleted += (_, qso) => _ = link?.SendDeletedAsync(qso);
        Check = new CheckWindowSources(positions[0], Calls, Bandmap);
        Available = new AvailableStations(positions[0], Bandmap);
        Save(Settings with { ContestNumber = contestNumber });
        ContestChanged?.Invoke(this, EventArgs.Empty);
    }

    /// A frequency on the band a number was taken on. The message carries a
    /// frequency because N1MM's does, and both ends read nothing off it but the
    /// band.
    private static Frequency SomewhereOn(Band? band) => band?.Low ?? Frequency.Zero;

    /// One entry position per radio, and one when there is no radio at all.
    private int PositionCount => Math.Max(1, Settings.Radios.Count(r => r.IsEnabled));

    /// Starts, restarts or stops the link to the other stations of a
    /// multi-operator entry, following what the settings now say.
    public void ApplyNetworkSettings()
    {
        announcing?.Stop();
        network?.Dispose();
        link?.Dispose();
        network = null;
        if (!Settings.NetworkEnabled)
        {
            Changed?.Invoke(this, EventArgs.Empty);
            return;
        }
        network = new StationNetwork(
            Settings.NetworkPort,
            Settings.NetworkStationName.Length > 0 ? Settings.NetworkStationName : Environment.MachineName,
            Settings.NetworkPeers);
        // the socket thread must not touch the log: every other change to it is
        // made where the windows read it
        network.UpdateArrived += (_, update) =>
            Dispatcher.UIThread.Post(() => TakeFromNetwork(update));
        network.Start();
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Starts, restarts or stops the link to the other logging computers. It is
    /// separate from `ApplyNetworkSettings` because the two are separate
    /// networks: one carries XML to other programs, the other carries contacts
    /// to the other computers of this entry.
    /// What this computer is called on the network of the entry, which is also
    /// what every contact it logs is stamped with.
    public string ComputerName =>
        Settings.NetworkStationName.Length > 0 ? Settings.NetworkStationName : Environment.MachineName;

    public void ApplyStationLinkSettings()
    {
        link?.Dispose();
        link = null;
        if (!Settings.StationLinkEnabled)
        {
            Changed?.Invoke(this, EventArgs.Empty);
            return;
        }
        link = new StationLink(
            ComputerName,
            Settings.StationLinkVersion,
            Settings.StationNumber,
            Settings.StationLinkPort)
        {
            Operator = Settings.Station.Callsign,
        };
        // the socket thread must not touch the log: every other change to it is
        // made where the windows read it
        link.UpdateArrived += (_, update) =>
            Dispatcher.UIThread.Post(() => TakeFromNetwork(update));
        // the resync reads the log rather than being handed it, and another
        // station can ask for a rescore when its resync is done
        link.Log = new SessionContactLog(this);
        link.RescoreRequested += (_, _) =>
            Dispatcher.UIThread.Post(() => Rescore(DateTime.MinValue));
        link.SerialNumbersReset += (_, _) =>
            Dispatcher.UIThread.Post(ResetSerialNumbers);
        link.CallStacked += (_, stacked) =>
            Dispatcher.UIThread.Post(() => TakeStackedCall(stacked));
        link.NumberReserved += (_, taken) =>
            Dispatcher.UIThread.Post(() => TakeReservedNumber(taken));
        link.SerialNumbersArrived += (_, numbers) =>
            Dispatcher.UIThread.Post(() => Logging?.Numbers.Merge(numbers));
        foreach (string peer in Settings.StationLinkPeers)
        {
            if (Peer(peer) is var (name, address, port))
            {
                link.AddStation(name, address, port);
            }
        }
        link.Start();
        // where this station is has a dozen places it can change from — the
        // radio moving, a band button, a QSY typed into the callsign box, run
        // turning on — so it is read once a second and sent when it has
        // changed, rather than announced from each of them
        announcing?.Stop();
        announced = default;
        statusSent = default;
        announcing = new DispatcherTimer { Interval = TimeSpan.FromSeconds(1) };
        announcing.Tick += (_, _) =>
        {
            AnnounceWhereIAm();
            SayHowIAmDoing();
        };
        announcing.Start();
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Tells the other stations where this one is, if it has moved. The
    /// frequency goes out on its own — N1MM's `FREQ` — and everything else
    /// about the position rides in the `STATUS` that follows it. In a
    /// multi-single entry this is what the other operators watch: two stations
    /// on one band is a contact nobody can make.
    private void AnnounceWhereIAm()
    {
        if (link is null || Position is not { } position)
        {
            return;
        }
        (Frequency, string, bool, int) now =
            (position.Frequency, position.Mode.Name, position.IsRunning, position.RadioNumber);
        if (now == announced)
        {
            return;
        }
        bool moved = announced.Where != position.Frequency;
        announced = now;
        if (moved)
        {
            _ = link.SendFrequencyAsync(position.Frequency);
        }
        // the mode, run and the rest of it ride in `STATUS`, which is sent
        // again now rather than waiting out the rest of its interval
        statusSent = default;
    }

    /// True while this station is the second run radio of a two-radio
    /// position, which is N1MM's Run1/Run2 switch on the network status window.
    /// It goes out in every `STATUS` and is what the other stations read in
    /// their `R/M` column.
    public bool IsRun2
    {
        get;
        set
        {
            field = value;
            statusSent = default;
            Changed?.Invoke(this, EventArgs.Empty);
        }
    }

    /// Starts the serial numbers again from the log: the next number becomes
    /// the highest one in it plus one. The contacts already logged keep the
    /// numbers they were sent with. Nothing is sent but `RESETQSONRS`, as in
    /// N1MM: each station works the same number out of its own copy of the log.
    public void ResetSerialNumbers()
    {
        if (Logging is not null)
        {
            Logging.RestartNumbers();
            Changed?.Invoke(this, EventArgs.Empty);
        }
    }

    /// A serial number another station has taken. It is noted here so this
    /// station counts past it. A number at or below one this station has
    /// already used says the sender is behind, and it is sent the highest
    /// number for each band so it can count on from the right one, which is
    /// what N1MM answers with.
    private void TakeReservedNumber(ReservedNumberMessage taken)
    {
        if (Logging is not { } logging)
        {
            return;
        }
        if (!logging.Numbers.Note(taken.Number, Bands.ForFrequency(taken.Frequency)))
        {
            _ = link?.SendSerialNumbersAsync(logging.Numbers.Snapshot());
        }
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// A callsign another station handed to this one. It goes on the call stack
    /// of the radio the operator is on, which is where the entry window takes
    /// them from.
    private void TakeStackedCall(StackedCall stacked)
    {
        if (Position is not { } position || stacked.Call.Length == 0)
        {
            return;
        }
        position.Stack.Add(stacked.Call, IsNewMultiplier(stacked));
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Whether a stacked call is worth a multiplier here, which is what decides
    /// where it goes in the stack. A call with no contact behind it is judged
    /// on the callsign alone.
    private bool IsNewMultiplier(StackedCall stacked) =>
        Logging is not null
        && (stacked.Contact is { } contact
            ? Logging.Log.Judge(contact).NewMultipliers.Count > 0
            : Logging.Log.Judge(new Qso
            {
                Id = "",
                TimestampUtc = DateTime.UtcNow,
                Call = Callsign.Parse(stacked.Call),
                Frequency = Position?.Frequency ?? Frequency.Zero,
                Mode = Position?.Mode ?? Modes.Cw,
                ContestName = Logging.Contest.Name,
            }).NewMultipliers.Count > 0);

    /// Scores the log again and writes the points and multiplier flags from
    /// `fromUtc` on back to the database. Returns how many rows were written.
    /// Another station asks for this at the end of a resync, and the rescore
    /// tab of the network status window asks for it by hand.
    public int Rescore(DateTime fromUtc) => Logging?.Rescore(fromUtc) ?? 0;

    /// The `STATUS` message: everything the other operators' network status
    /// windows show about this station, whether anything has changed or not. It
    /// goes out on N1MM's own interval, and the rates in it are read out of the
    /// log each time.
    private void SayHowIAmDoing()
    {
        if (link is null || Position is not { } position
            || DateTime.UtcNow - statusSent < StatusInterval)
        {
            return;
        }
        statusSent = DateTime.UtcNow;
        TimeSpan off = Logging?.Contest.MinimumOffTime ?? TimeSpan.FromMinutes(30);
        IReadOnlyList<Qso> qsos = Logging?.Log.Qsos ?? [];
        _ = link.SendStatusAsync(new StationStatus(
            link.Me.PassFrequency,
            position.Frequency,
            position.IsRunning,
            link.Operator,
            position.Mode,
            Rates.PerHour(qsos, 10, DateTime.UtcNow, off),
            Rates.PerHour(qsos, 100, DateTime.UtcNow, off),
            Logging?.Instance.OperatorCategory ?? "",
            Logging?.Instance.TransmitterCategory ?? "",
            Countries?.Version ?? "",
            IsRun2));
    }

    /// A station named by hand, written `RUN-PC@192.168.1.5` with `:port` on
    /// the end when that station is not on the usual one. Null for anything
    /// else, because a line the operator has half typed is not an address.
    private (string Name, string Address, int Port)? Peer(string text)
    {
        string[] parts = text.Split('@');
        if (parts.Length != 2 || parts[0].Trim().Length == 0)
        {
            return null;
        }
        string[] host = parts[1].Split(':');
        return (
            parts[0].Trim(),
            host[0].Trim(),
            host.Length > 1 && int.TryParse(host[1], out int given) ? given : Settings.StationLinkPort);
    }

    /// What another station did to its log, applied to ours. Nothing goes back
    /// out to the network, and the contact is scored here from the rules
    /// instead of trusting what the sender put in the message.
    private void TakeFromNetwork(ContactUpdate update)
    {
        if (Logging is null)
        {
            return;
        }
        if (!Settings.LogQsosAtAllStations && update is not ContactsCleared)
        {
            return;
        }
        switch (update)
        {
            case ContactLogged logged:
                Logging.AddFromNetwork(logged.Qso);
                break;
            case ContactReplaced replaced:
                Logging.ReplaceFromNetwork(replaced.Qso, replaced.OldCall, replaced.OldTimestampUtc);
                break;
            case ContactDeleted deleted:
                Logging.DeleteFromNetwork(deleted.Id, deleted.Call, deleted.TimestampUtc);
                break;
            case ContactsCleared cleared:
                Logging.ClearFromNetwork(cleared.StationName, cleared.FromUtc, cleared.Length);
                break;
        }
    }

    /// Starts, restarts or stops the keyer, following what the settings say.
    /// A keyer that will not open is reported; the program keeps running
    /// without one.
    public void ApplyKeyerSettings()
    {
        alternating?.Dispose();
        alternating = null;
        keyer?.Dispose();
        keyer = null;
        switch (Settings.KeyerKind.ToLowerInvariant())
        {
            case "cwdaemon":
                keyer = new CwDaemonSender(Settings.KeyerHost, Settings.KeyerPort);
                break;
            case "winkeyer":
                WinkeyerSender winkeyer = new(Settings.KeyerSerialPort);
                winkeyer.Open();
                keyer = winkeyer;
                break;
        }
        if (keyer is not null)
        {
            _ = keyer.SetSpeedAsync(Settings.KeyerSpeed);
            alternating = new AlternatingCq(
                keyer,
                CallCqOnAsync,
                TimeSpan.FromMilliseconds(Settings.AlternatingCqGapMs));
        }
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Starts the digital engine under Wine and returns it. The engine that is
    /// already running is handed back rather than started again.
    public async Task<MmttyEngine> StartDigitalAsync()
    {
        if (digital is { IsConnected: true } running)
        {
            return running;
        }
        StopDigital();
        MmttyOptions options = new()
        {
            EnginePath = Settings.DigitalEnginePath,
            Number = ActiveRadioNumber,
            Window = Enum.TryParse(Settings.DigitalEngineWindow, ignoreCase: true, out EngineWindow window)
                ? window
                : EngineWindow.Normal,
            OnTop = Settings.DigitalEngineOnTop,
            PttPort = Settings.DigitalPttPort.Trim().Length > 0 ? Settings.DigitalPttPort : null,
        };
        WineBridgeChannel channel = new(
            Settings.DigitalBridgePath,
            Settings.DigitalWinePrefix.Trim().Length > 0 ? Settings.DigitalWinePrefix : null,
            Settings.DigitalWineCommand.Trim().Length > 0 ? Settings.DigitalWineCommand : "wine",
            Paths.Diagnostics);
        MmttyEngine started = new(channel, options);
        await started.StartAsync();
        digital = started;
        digitalSender = new DigitalEngineSender(started, Settings.DigitalBaud);
        Changed?.Invoke(this, EventArgs.Empty);
        return started;
    }

    public void StopDigital()
    {
        digitalSender?.Dispose();
        digitalSender = null;
        digital?.Dispose();
        digital = null;
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Opens a connection per enabled radio. A second one makes the station
    /// SO2R: both are read, but only the one the operator is on drives the
    /// entry window.
    public void ConnectRadios()
    {
        DisposeRadios();
        int number = 1;
        foreach (StoredRadio configured in Settings.Radios.Where(r => r.IsEnabled))
        {
            RigctldRadio opened = new(configured.Host, configured.Port, number++);
            opened.Moved += (_, state) => RadioMoved(opened, state);
            opened.ConnectionChanged += (_, _) => Changed?.Invoke(this, EventArgs.Empty);
            radios.Add(opened);
            opened.Start();
        }
        if (Logging is not null && positions.Count != PositionCount)
        {
            OpenContest(Logging.Instance.ContestNumber);
            return;
        }
        activeRadio = Math.Min(activeRadio, Math.Max(0, positions.Count - 1));
        Changed?.Invoke(this, EventArgs.Empty);
    }

    public void DisconnectRadios()
    {
        DisposeRadios();
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Moves the operator to the other radio. The entry window follows where
    /// that radio is sitting, and contacts are logged against its number.
    public void SwapRadio()
    {
        if (positions.Count < 2)
        {
            return;
        }
        MoveToRadio(positions[(activeRadio + 1) % positions.Count].RadioNumber);
    }

    /// Moves the operator to a radio by number. Alternating CQ calls this from
    /// the keyer's thread, so everything it raises is posted by the windows.
    public void MoveToRadio(int radioNumber)
    {
        int at = positions.FindIndex(p => p.RadioNumber == radioNumber);
        if (at < 0 || at == activeRadio)
        {
            return;
        }
        activeRadio = at;
        _ = FollowActiveRadioAsync();
        Changed?.Invoke(this, EventArgs.Empty);
        ActiveRadioChanged?.Invoke(this, ActiveRadioNumber);
    }

    /// Moves to the radio and sends its CQ message, which is F1. Used by
    /// alternating CQ; the operator's own F1 goes through the entry window.
    private async Task CallCqOnAsync(int radioNumber)
    {
        OperatingPosition position = positions.FirstOrDefault(p => p.RadioNumber == radioNumber)
            ?? throw new InvalidOperationException($"there is no radio {radioNumber}");
        if (keyer is null)
        {
            throw new InvalidOperationException("there is no keyer");
        }
        string template = Messages
            .For(position.Mode.Category, Settings.CwMessageFile, Settings.PhoneMessageFile)
            .Keys(position.IsRunning)[Esm.CallCq]
            .Message;
        if (template.Length == 0)
        {
            throw new InvalidOperationException("F1 has no message — Config ▸ Keyer and messages");
        }
        MoveToRadio(radioNumber);
        await PointTransmitAtAsync(radioNumber).ConfigureAwait(false);
        await keyer.SendAsync(MessageExpander.Expand(template, position, Other(position))).ConfigureAwait(false);
    }

    /// Puts both radios in the headphones, or goes back to one. An operator
    /// listens to the second radio while the first is sending.
    public void ToggleListenToBoth()
    {
        IsListeningToBoth = !IsListeningToBoth;
        _ = FollowActiveRadioAsync();
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// Points the box at the radio about to transmit. Called before keying, so
    /// a message never goes out of the radio the operator has just left.
    public Task PointTransmitAtAsync(int radioNumber) =>
        box?.SetTransmitAsync(radioNumber) ?? Task.CompletedTask;

    /// Starts, restarts or stops the SO2R box, following what the settings say.
    public void ApplySo2rSettings()
    {
        box?.Dispose();
        box = Settings.So2rBoxPort.Length > 0 ? OtrspBox.Open(Settings.So2rBoxPort) : null;
        _ = FollowActiveRadioAsync();
        Changed?.Invoke(this, EventArgs.Empty);
    }

    private async Task FollowActiveRadioAsync()
    {
        if (box is null)
        {
            return;
        }
        try
        {
            await box.SetTransmitAsync(ActiveRadioNumber).ConfigureAwait(false);
            await box.SetReceiveAsync(ActiveRadioNumber, IsListeningToBoth).ConfigureAwait(false);
        }
        catch (Exception e) when (e is IOException or InvalidOperationException)
        {
            box.Dispose();
            box = null;
        }
    }

    /// Raised when the operator moves to the other radio, so the entry windows
    /// can hand the keyboard over and the SO2R box can follow.
    public event EventHandler<int>? ActiveRadioChanged;

    /// The radio the operator is not on still moves, and the bandmap shows it,
    /// but it must not drag the entry window off the contact being worked.
    private void RadioMoved(Radio moved, RadioState state)
    {
        OperatingPosition? position = positions.FirstOrDefault(p => p.RadioNumber == moved.Number);
        if (position is null)
        {
            return;
        }
        position.Tune(state.Frequency, state.Mode, state.TransmitFrequency);
    }

    private void DisposeRadios()
    {
        foreach (RigctldRadio open in radios)
        {
            open.Dispose();
        }
        radios.Clear();
    }

    public void ConnectCluster()
    {
        cluster?.Dispose();
        cluster = new ClusterClient(
            Settings.ClusterHost,
            Settings.ClusterPort,
            Settings.ClusterLogonCall.Length > 0 ? Settings.ClusterLogonCall : Settings.Station.Callsign,
            Settings.ClusterCommands,
            Settings.ClusterPassword,
            autoLogon: Settings.ClusterAutoLogon,
            keepAliveInterval: TimeSpan.FromMinutes(Math.Max(1, Settings.ClusterKeepAliveMinutes)));
        cluster.SpotArrived += (_, spot) => TakeSpot(spot);
        cluster.ConnectionChanged += (_, _) => Changed?.Invoke(this, EventArgs.Empty);
        cluster.Start();
    }

    public void DisconnectCluster()
    {
        cluster?.Dispose();
        cluster = null;
        Changed?.Invoke(this, EventArgs.Empty);
    }

    /// A spot the node sent. It waits for the next flush rather than going
    /// straight onto the bandmap.
    private void TakeSpot(Spot spot)
    {
        lock (arrivingGuard)
        {
            arriving.Add(spot);
        }
    }

    /// The spots that arrived since the last flush, filtered and moved about,
    /// put on the bandmap in one go.
    private void FlushSpots()
    {
        List<Spot> batch;
        lock (arrivingGuard)
        {
            if (arriving.Count == 0)
            {
                return;
            }
            batch = [.. arriving];
            arriving.Clear();
        }
        List<Spot> keeping = [];
        foreach (Spot spot in batch)
        {
            if (spotFilter.Accepts(spot))
            {
                keeping.Add(Settings.RandomizeSpots
                    ? SpotJitter.Shifted(spot, BandPlan, jitter, IsDupe(spot))
                    : spot);
            }
        }
        if (keeping.Count > 0)
        {
            Bandmap.AddRange(keeping);
        }
    }

    /// Whether the station has already been worked, which decides whether a
    /// spot is moved about: N1MM leaves a dupe where it is.
    private bool IsDupe(Spot spot) =>
        Logging is not null && Logging.Log.Judge(new Qso
        {
            Id = "",
            TimestampUtc = spot.AtUtc,
            Call = spot.Call,
            Frequency = spot.Frequency,
            Mode = Position?.Mode ?? Modes.Cw,
            ContestName = Logging.Contest.Name,
        }) is { IsDupe: true };

    private void ApplySpotSettings()
    {
        spotFilter = Settings.SpotFilter.ToFilter(BandPlan, Settings.Station, Countries, Calls, History);
        Bandmap.Lifetime = TimeSpan.FromMinutes(Math.Max(1, Settings.SpotTimeoutMinutes));
    }

    public void ReloadSupportFiles()
    {
        Countries = LoadCountryFile(Paths.CountryFile);
        Calls = LoadCallDatabase(Paths.CallDatabaseFile);
        History = LoadCallHistory(Settings.CallHistoryFile);
        Registry = ContestRegistry.FromFolder(Paths.UserDefinedContests, out _, Paths.SupportFiles);
        ApplySpotSettings();
        if (Logging is not null)
        {
            OpenContest(Logging.Instance.ContestNumber);
        }
        Changed?.Invoke(this, EventArgs.Empty);
    }

    public void Dispose()
    {
        StopDigital();
        spotFlush.Dispose();
        DisposeRadios();
        cluster?.Dispose();
        announcing?.Stop();
        network?.Dispose();
        link?.Dispose();
        alternating?.Dispose();
        keyer?.Dispose();
        box?.Dispose();
        store?.Dispose();
    }

    private static ModeCategory ModeCategoryOf(ContestInstance instance) =>
        instance.ModeCategory.ToUpperInvariant() switch
        {
            "SSB" or "PH" or "PHONE" => ModeCategory.Phone,
            "RTTY" or "DIGI" or "DIGITAL" => ModeCategory.Digital,
            _ => ModeCategory.Cw,
        };

    /// Without a country file the program still runs; country and continent
    /// scoring just loses accuracy.
    private static CountryFile? LoadCountryFile(string path)
    {
        try
        {
            return File.Exists(path) ? CountryFile.Parse(File.ReadAllText(path)) : null;
        }
        catch (Exception e) when (e is FormatException or IOException)
        {
            return null;
        }
    }

    /// A file that will not parse is reported by coming back empty rather than
    /// stopping the program before a contest.
    private static CallHistory LoadCallHistory(string path)
    {
        try
        {
            return path.Length > 0 && File.Exists(path)
                ? CallHistory.Parse(File.ReadAllText(path))
                : CallHistory.Empty;
        }
        catch (Exception e) when (e is FormatException or IOException)
        {
            return CallHistory.Empty;
        }
    }

    private static CallDatabase LoadCallDatabase(string path)
    {
        try
        {
            return File.Exists(path) ? CallDatabase.Parse(File.ReadAllText(path)) : CallDatabase.Empty;
        }
        catch (Exception e) when (e is FormatException or IOException)
        {
            return CallDatabase.Empty;
        }
    }
}