Read call history files, and fill the exchange from them

N1MM's format, so a file published for a contest is read as it is: # comments,
!!Order!! naming the columns of the lines after it, semicolons in preference to
commas so user text can hold a comma, and a default column order for a file
that names none. The directives that change what is stored are acted on;
!!Order!! can appear again part way through, because these files are usually
several files stuck together.

Leaving the callsign box fills what the file knows into the exchange boxes that
are still empty. A box with something in it is left alone: what the station
actually sends beats what somebody published months ago. The zone comes from
the CqZone or the ITUZone column depending on which the contest asks for, and a
file with no Sect falls back to State.

The check window's two missing columns are in. History lists matching calls
from the file. Exchange is not about callsigns at all: it offers the values the
exchange box with the cursor in it can hold, which is what N1MM's exchange pane
does — it searches the contest's list of valid exchanges, not the log.
CheckCandidate.Call is now Text, because an exchange value is not a call.

The section-validating directives are read and passed over rather than acted
on. Acting on them means holding N1MM's section lists and its rules about
retired sections, and getting that wrong throws away good data.

Running it caught what the unit tests could not: the exchange was filled and
scored but the boxes on screen still looked empty, because nothing resynced
them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.App/AppSession.cs

@@ -33,6 +33,7 @@ public sealed class AppSession : IDisposable
         paths.CreateFolders();
         Countries = LoadCountryFile(paths.CountryFile);
         Calls = LoadCallDatabase(paths.CallDatabaseFile);
+        History = LoadCallHistory(settings.CallHistoryFile);
         Registry = ContestRegistry.FromFolder(paths.UserDefinedContests, out IReadOnlyList<string> problems);
         UserDefinedContestProblems = problems;
     }
@@ -49,6 +50,10 @@ public sealed class AppSession : IDisposable
 
     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();
 
     /// The contest in progress: one log and one score, however many radios.
@@ -133,7 +138,8 @@ public sealed class AppSession : IDisposable
             ?? 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);
+        Logging = new ContestSession(
+            Store, contest, instance, Settings.Station.ToStationInfo(), Countries, History);
         positions.Clear();
         for (int number = 1; number <= PositionCount; number++)
         {
@@ -384,6 +390,7 @@ public sealed class AppSession : IDisposable
     {
         Countries = LoadCountryFile(Paths.CountryFile);
         Calls = LoadCallDatabase(Paths.CallDatabaseFile);
+        History = LoadCallHistory(Settings.CallHistoryFile);
         Registry = ContestRegistry.FromFolder(Paths.UserDefinedContests, out _);
         if (Logging is not null)
         {
@@ -424,6 +431,22 @@ public sealed class AppSession : IDisposable
         }
     }
 
+    /// 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

src/Nonemm.App/Configuration/Settings.cs

@@ -43,6 +43,10 @@ public sealed record Settings
 
     public IReadOnlyList<string> NetworkPeers { get; init; } = [];
 
+    /// The call history file for this contest, or empty for none. They are
+    /// published per contest, so this is not a fixed name.
+    public string CallHistoryFile { get; init; } = "";
+
     /// The serial port of an SO2R box speaking OTRSP, or empty for none. The
     /// box routes the transmitter and the headphones between the two radios.
     public string So2rBoxPort { get; init; } = "";

src/Nonemm.App/Windows/CheckWindow.axaml.cs

@@ -11,12 +11,10 @@ namespace Nonemm.App.Windows;
 public sealed partial class CheckWindow : RefreshableWindow
 {
     private readonly AppSession session;
-    private readonly Func<string> typed;
 
-    public CheckWindow(AppSession session, Func<string> typed)
+    public CheckWindow(AppSession session)
     {
         this.session = session;
-        this.typed = typed;
         InitializeComponent();
         Refresh();
     }
@@ -29,8 +27,14 @@ public sealed partial class CheckWindow : RefreshableWindow
         {
             return;
         }
+        IReadOnlyList<CheckColumn> columns = session.Check.Columns();
+        Columns.ColumnDefinitions.Clear();
+        foreach (CheckColumn _ in columns)
+        {
+            Columns.ColumnDefinitions.Add(new ColumnDefinition(GridLength.Star));
+        }
         int at = 0;
-        foreach (CheckColumn column in session.Check.Columns(typed()))
+        foreach (CheckColumn column in columns)
         {
             Control panel = BuildColumn(column);
             Grid.SetColumn(panel, at++);
@@ -52,7 +56,7 @@ public sealed partial class CheckWindow : RefreshableWindow
         {
             panel.Children.Add(new TextBlock
             {
-                Text = candidate.Call,
+                Text = candidate.Text,
                 FontFamily = new FontFamily("monospace"),
                 FontSize = 14,
                 Foreground = Verdicts.Colour(candidate.Verdict),
@@ -71,6 +75,8 @@ public sealed partial class CheckWindow : RefreshableWindow
     {
         CheckSource.Log => "Log",
         CheckSource.Database => "Master",
-        _ => "Bandmap",
+        CheckSource.History => "History",
+        CheckSource.Bandmap => "Bandmap",
+        _ => "Exchange",
     };
 }

src/Nonemm.App/Windows/EntryWindow.Menu.cs

@@ -226,7 +226,7 @@ public sealed partial class EntryWindow
 
     private void OnShowLog(object? sender, RoutedEventArgs e) => Show(() => new LogWindow(session));
 
-    private void OnShowCheck(object? sender, RoutedEventArgs e) => Show(() => new CheckWindow(session, () => Logging?.Entry.Call ?? ""));
+    private void OnShowCheck(object? sender, RoutedEventArgs e) => Show(() => new CheckWindow(session));
 
     private void OnShowBandmap(object? sender, RoutedEventArgs e) => Show(() => new BandmapWindow(session, Tune));
 
@@ -329,6 +329,27 @@ public sealed partial class EntryWindow
         BuildFunctionKeys();
     }
 
+    /// Call history files are published per contest, so the operator points at
+    /// one rather than the program looking in a fixed place.
+    private async void OnCallHistoryFile(object? sender, RoutedEventArgs e)
+    {
+        IReadOnlyList<IStorageFile> files = await StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
+        {
+            Title = "Call history file",
+            AllowMultiple = false,
+            SuggestedStartLocation = await Folder(session.Paths.SupportFiles),
+        });
+        if (files.FirstOrDefault()?.TryGetLocalPath() is not { } path)
+        {
+            return;
+        }
+        session.Save(session.Settings with { CallHistoryFile = path });
+        session.ReloadSupportFiles();
+        Status(session.History.Count > 0
+            ? $"{session.History.Count} calls read from {Path.GetFileName(path)}"
+            : $"{Path.GetFileName(path)} holds no calls we could read");
+    }
+
     private async void OnDownloadCountryFile(object? sender, RoutedEventArgs e) =>
         await Download(
             downloader => downloader.DownloadCountryFileAsync(session.Paths.CountryFile),
@@ -343,7 +364,7 @@ public sealed partial class EntryWindow
     {
         session.ReloadSupportFiles();
         Status($"country file {(session.Countries is null ? "missing" : "loaded")}, " +
-               $"{session.Calls.Count} callsigns");
+               $"{session.Calls.Count} callsigns, {session.History.Count} in the call history");
     }
 
     private async Task Download(Func<SupportFileDownloader, Task<string>> fetch, string what)

src/Nonemm.App/Windows/EntryWindow.axaml

@@ -57,6 +57,8 @@
         <MenuItem Header="_Network…" Click="OnNetworkSettings" />
         <MenuItem Header="_Keyer and messages…" Click="OnKeyerSettings" />
         <Separator />
+        <MenuItem Header="Call _History File…" Click="OnCallHistoryFile" />
+        <Separator />
         <MenuItem Header="Download Country _File" Click="OnDownloadCountryFile" />
         <MenuItem Header="Download Check _Partial File" Click="OnDownloadCallDatabase" />
         <MenuItem Header="Reload Support Files" Click="OnReloadSupportFiles" />

src/Nonemm.App/Windows/EntryWindow.axaml.cs

@@ -315,6 +315,12 @@ public sealed partial class EntryWindow : Window
         }
         if (forward)
         {
+            // leaving the callsign box is the moment the call is settled, which
+            // is when the call history can say what the exchange will be
+            if (Logging.Entry.Focus == 0 && Logging.FillFromHistory())
+            {
+                SyncBoxes();
+            }
             Logging.Entry.Advance();
         }
         else

src/Nonemm.Contests/ExchangeValues.cs

@@ -0,0 +1,22 @@
+using Nonemm.Contests.Multipliers;
+
+namespace Nonemm.Contests;
+
+/// Every value an exchange field can hold, where the field has a list behind
+/// it. A serial number or a report has none, so those get an empty list rather
+/// than a guess.
+public static class ExchangeValues
+{
+    private static readonly IReadOnlyList<string> StatesAndProvincesList =
+        [.. StatesAndProvinces.AllStates.Concat(StatesAndProvinces.Provinces).Order(StringComparer.Ordinal)];
+
+    private static readonly IReadOnlyList<string> Sections =
+        [.. ArrlSections.All.Order(StringComparer.Ordinal)];
+
+    public static IReadOnlyList<string> For(ExchangeFieldKind kind) => kind switch
+    {
+        ExchangeFieldKind.ArrlSection => Sections,
+        ExchangeFieldKind.UsStateOrCanadianProvince => StatesAndProvincesList,
+        _ => [],
+    };
+}

src/Nonemm.Core/Calls/CallHistory.cs

@@ -0,0 +1,167 @@
+using System.Globalization;
+
+namespace Nonemm.Core.Calls;
+
+/// A call history file: what is already known about a station before it sends
+/// its exchange. N1MM's format, so the files published for a contest can be
+/// used as they are.
+///
+/// Lines starting with `#` are comments. A line whose first field is `!!Name!!`
+/// is a directive rather than data, and `!!Order!!` names the columns of the
+/// lines that follow. Fields are separated by semicolons if the line holds one,
+/// and by commas otherwise.
+public sealed class CallHistory
+{
+    /// The columns a file is read with when it names none.
+    private static readonly string[] DefaultOrder =
+    [
+        "CALL", "NAME", "LOC1", "LOC2", "SECT", "STATE", "CK",
+        "BIRTHDATE", "EXCH1", "MISC", "POWER", "CQZONE", "ITUZONE", "USERTEXT",
+    ];
+
+    private readonly Dictionary<string, CallHistoryEntry> entries;
+
+    private CallHistory(Dictionary<string, CallHistoryEntry> entries) => this.entries = entries;
+
+    public static readonly CallHistory Empty = new([]);
+
+    public int Count => entries.Count;
+
+    /// Null for a station the file says nothing about.
+    public CallHistoryEntry? Find(string call) =>
+        entries.TryGetValue(call.Trim().ToUpperInvariant(), out CallHistoryEntry? found)
+            ? found
+            : null;
+
+    /// Every call in the file, for the check window to match against.
+    public IReadOnlyCollection<string> Calls => entries.Keys;
+
+    public static CallHistory Parse(string text)
+    {
+        Dictionary<string, CallHistoryEntry> found = new(StringComparer.Ordinal);
+        string[] order = DefaultOrder;
+        bool fourCharacterGrid = false;
+        bool useAlternateGrid = true;
+        bool mapStateToSection = false;
+        bool appendUserText = true;
+
+        foreach (string line in text.Split('\n'))
+        {
+            string trimmed = line.Trim();
+            if (trimmed.Length == 0 || trimmed.StartsWith('#'))
+            {
+                continue;
+            }
+            string[] fields = Split(trimmed);
+            string first = fields[0].Trim().ToUpperInvariant();
+            if (first.StartsWith("!!", StringComparison.Ordinal))
+            {
+                switch (first)
+                {
+                    case "!!ORDER!!":
+                        order = [.. fields.Skip(1).Select(f => f.Trim().ToUpperInvariant())];
+                        break;
+                    case "!!FOURCHARGRIDSQ!!":
+                        fourCharacterGrid = true;
+                        break;
+                    case "!!NOLOC2ALTGRID!!":
+                        useAlternateGrid = false;
+                        break;
+                    case "!!MAPSTATETOSECT!!":
+                        mapStateToSection = true;
+                        break;
+                    case "!!APPENDUSERTEXT!!":
+                        appendUserText = true;
+                        break;
+                    case "!!NOAPPENDUSERTEXT!!":
+                        appendUserText = false;
+                        break;
+                }
+                // the rest are validation directives, and validating a section
+                // list we do not hold would throw data away
+                continue;
+            }
+            CallHistoryEntry? entry = Read(fields, order, fourCharacterGrid, useAlternateGrid, mapStateToSection);
+            if (entry is not null)
+            {
+                found[entry.Call] = Merge(found.GetValueOrDefault(entry.Call), entry, appendUserText);
+            }
+        }
+        return new CallHistory(found);
+    }
+
+    /// A call can appear more than once. Later lines win, except that user text
+    /// is added to rather than replaced unless the file says otherwise.
+    private static CallHistoryEntry Merge(CallHistoryEntry? earlier, CallHistoryEntry later, bool append)
+    {
+        if (earlier is null)
+        {
+            return later;
+        }
+        if (!append || earlier.UserText.Length == 0 || later.UserText.Length == 0)
+        {
+            return later;
+        }
+        return later with { UserText = $"{earlier.UserText} {later.UserText}" };
+    }
+
+    private static CallHistoryEntry? Read(
+        string[] fields,
+        string[] order,
+        bool fourCharacterGrid,
+        bool useAlternateGrid,
+        bool mapStateToSection)
+    {
+        string call = At(fields, order, "CALL").ToUpperInvariant();
+        if (call.Length == 0)
+        {
+            return null;
+        }
+        string section = At(fields, order, "SECT");
+        string state = At(fields, order, "STATE");
+        return new CallHistoryEntry
+        {
+            Call = call,
+            Name = At(fields, order, "NAME"),
+            GridSquare = Grid(At(fields, order, "LOC1"), fourCharacterGrid),
+            AlternateGridSquare = useAlternateGrid
+                ? Grid(At(fields, order, "LOC2"), fourCharacterGrid)
+                : "",
+            Section = section.Length == 0 && mapStateToSection ? state : section,
+            State = state,
+            Check = Number(At(fields, order, "CK")),
+            Exchange1 = At(fields, order, "EXCH1"),
+            MiscText = At(fields, order, "MISC", "MISCTEXT"),
+            Power = At(fields, order, "POWER"),
+            CqZone = Number(At(fields, order, "CQZONE")),
+            ItuZone = Number(At(fields, order, "ITUZONE")),
+            UserText = At(fields, order, "USERTEXT"),
+        };
+    }
+
+    /// N1MM takes semicolons in preference to commas, so a file whose user text
+    /// holds commas can still be read.
+    private static string[] Split(string line) =>
+        line.Contains(';', StringComparison.Ordinal) ? line.Split(';') : line.Split(',');
+
+    private static string At(string[] fields, string[] order, params string[] names)
+    {
+        foreach (string name in names)
+        {
+            int at = Array.IndexOf(order, name);
+            if (at >= 0 && at < fields.Length)
+            {
+                return fields[at].Trim();
+            }
+        }
+        return "";
+    }
+
+    private static string Grid(string grid, bool fourCharacters) =>
+        fourCharacters && grid.Length > 4 ? grid[..4].ToUpperInvariant() : grid.ToUpperInvariant();
+
+    private static int Number(string value) =>
+        int.TryParse(value, NumberStyles.Integer, CultureInfo.InvariantCulture, out int number)
+            ? number
+            : 0;
+}

src/Nonemm.Core/Calls/CallHistoryEntry.cs

@@ -0,0 +1,35 @@
+namespace Nonemm.Core.Calls;
+
+/// What a call history file says about one station. The fields are N1MM's, so
+/// a file written for N1MM means the same thing here.
+public sealed record CallHistoryEntry
+{
+    public required string Call { get; init; }
+
+    public string Name { get; init; } = "";
+
+    /// `Loc1` in the file.
+    public string GridSquare { get; init; } = "";
+
+    /// `Loc2`: a second grid for a station that operates from two places.
+    public string AlternateGridSquare { get; init; } = "";
+
+    public string Section { get; init; } = "";
+
+    public string State { get; init; } = "";
+
+    /// The two-digit year of first licensing, which Sweepstakes exchanges.
+    public int Check { get; init; }
+
+    public string Exchange1 { get; init; } = "";
+
+    public string MiscText { get; init; } = "";
+
+    public string Power { get; init; } = "";
+
+    public int CqZone { get; init; }
+
+    public int ItuZone { get; init; }
+
+    public string UserText { get; init; } = "";
+}

src/Nonemm.Session/CheckCandidate.cs

@@ -3,19 +3,24 @@ using Nonemm.Core.Calls;
 
 namespace Nonemm.Session;
 
-/// One callsign the check window offers, with what the log says about it so it
-/// is coloured the same as everywhere else.
-public sealed record CheckCandidate(string Call, PartialMatchQuality Quality, Verdict? Verdict);
+/// One thing the check window offers: a callsign in most columns, an exchange
+/// value in the exchange column. `Verdict` is what the log says about a call,
+/// so it is coloured the same as everywhere else, and null for anything that is
+/// not a call.
+public sealed record CheckCandidate(string Text, PartialMatchQuality Quality, Verdict? Verdict);
 
 /// Where a column of candidates came from. They stay apart because they answer
 /// different questions: the log is what this station copied itself, the
-/// database is a guess about the whole world, and the bandmap is somebody
-/// else's claim.
+/// database is a guess about the whole world, the call history is what was
+/// published before the contest, the bandmap is somebody else's claim, and the
+/// exchange column is not about callsigns at all.
 public enum CheckSource
 {
     Log,
     Database,
+    History,
     Bandmap,
+    Exchange,
 }
 
 /// One column of the check window.

src/Nonemm.Session/CheckWindowSources.cs

@@ -19,9 +19,12 @@ public sealed class CheckWindowSources
         this.bandmap = bandmap;
     }
 
-    public IReadOnlyList<CheckColumn> Columns(string typed, int limit = 24)
+    /// The columns are read off what the operator has typed: the callsign box
+    /// feeds the call columns, and whichever exchange box has the cursor feeds
+    /// the exchange column.
+    public IReadOnlyList<CheckColumn> Columns(int limit = 24)
     {
-        string query = typed.Trim().ToUpperInvariant();
+        string query = session.Entry.Call.Trim().ToUpperInvariant();
         return
         [
             Column(CheckSource.Log, LoggedCalls(), query, limit),
@@ -31,10 +34,36 @@ public sealed class CheckWindowSources
                 query.Length < PartialMatching.ShortestUsefulQuery
                     ? []
                     : database.Matches(query, limit).Select(Judged).ToList()),
+            Column(CheckSource.History, HistoryCalls(), query, limit),
             Column(CheckSource.Bandmap, SpottedCalls(), query, limit),
+            ExchangeColumn(limit),
         ];
     }
 
+    /// What the exchange box with the cursor in it could hold: the ARRL
+    /// sections, or the states and provinces. A serial number or a report has
+    /// no list behind it, so the column stays empty.
+    private CheckColumn ExchangeColumn(int limit)
+    {
+        int focus = session.Entry.Focus;
+        if (focus == 0)
+        {
+            return new CheckColumn(CheckSource.Exchange, 0, []);
+        }
+        ExchangeField field = session.Entry.Exchange[focus - 1];
+        IReadOnlyList<string> values = ExchangeValues.For(field.Kind);
+        string query = session.Entry[focus].Trim().ToUpperInvariant();
+        if (query.Length == 0)
+        {
+            return new CheckColumn(CheckSource.Exchange, values.Count, []);
+        }
+        List<CheckCandidate> found = [.. values
+            .Where(v => v.StartsWith(query, StringComparison.OrdinalIgnoreCase))
+            .Take(limit)
+            .Select(v => new CheckCandidate(v, PartialMatchQuality.Exact, null))];
+        return new CheckColumn(CheckSource.Exchange, values.Count, found);
+    }
+
     private CheckColumn Column(
         CheckSource source,
         IReadOnlyList<string> calls,
@@ -57,7 +86,7 @@ public sealed class CheckWindowSources
         return new CheckColumn(
             source,
             calls.Count,
-            found.OrderBy(c => c.Quality).ThenBy(c => c.Call, StringComparer.Ordinal).Take(limit).ToList());
+            found.OrderBy(c => c.Quality).ThenBy(c => c.Text, StringComparer.Ordinal).Take(limit).ToList());
     }
 
     private CheckCandidate Judged(PartialMatch match) =>
@@ -81,6 +110,8 @@ public sealed class CheckWindowSources
     private IReadOnlyList<string> LoggedCalls() =>
         session.Log.Qsos.Select(q => q.Call.Text).Distinct(StringComparer.Ordinal).ToList();
 
+    private IReadOnlyList<string> HistoryCalls() => [.. session.Session.History.Calls];
+
     private IReadOnlyList<string> SpottedCalls() =>
         bandmap.All().Select(s => s.Call.Text).Distinct(StringComparer.Ordinal).ToList();
 }

src/Nonemm.Session/ContestSession.cs

@@ -1,5 +1,6 @@
 using Nonemm.Contests;
 using Nonemm.Core;
+using Nonemm.Core.Calls;
 using Nonemm.Core.Country;
 using Nonemm.Storage;
 
@@ -20,10 +21,12 @@ public sealed class ContestSession
         Contest contest,
         ContestInstance instance,
         StationInfo me,
-        CountryFile? countries)
+        CountryFile? countries,
+        CallHistory? history = null)
     {
         this.store = store;
         Countries = countries;
+        History = history ?? CallHistory.Empty;
         Contest = contest;
         Instance = instance;
         Me = me;
@@ -45,6 +48,9 @@ public sealed class ContestSession
 
     public CountryFile? Countries { get; }
 
+    /// What was published about the stations in this contest before it started.
+    public CallHistory History { get; }
+
     /// Serial numbers count up across the station, not per radio.
     public int SentNumber { get; private set; }
 

src/Nonemm.Session/RadioPosition.cs

@@ -1,5 +1,6 @@
 using Nonemm.Contests;
 using Nonemm.Core;
+using Nonemm.Core.Calls;
 using Nonemm.Core.Country;
 using Nonemm.Storage;
 
@@ -87,6 +88,53 @@ public sealed class RadioPosition
         return stored;
     }
 
+    /// Fills what the call history knows into the exchange boxes that are still
+    /// empty. What the other station actually sends wins, so a box with
+    /// something in it is left alone. Returns true when anything was filled.
+    public bool FillFromHistory()
+    {
+        CallHistoryEntry? known = Session.History.Find(Entry.Call);
+        if (known is null)
+        {
+            return false;
+        }
+        bool filled = false;
+        for (int at = 0; at < Entry.Exchange.Count; at++)
+        {
+            string value = ValueFor(known, Entry.Exchange[at]);
+            if (value.Length == 0 || Entry[at + 1].Trim().Length > 0)
+            {
+                continue;
+            }
+            Entry[at + 1] = value;
+            filled = true;
+        }
+        if (filled)
+        {
+            Session.NotifyChanged();
+        }
+        return filled;
+    }
+
+    private static string ValueFor(CallHistoryEntry known, ExchangeField field) => field.Slot switch
+    {
+        ExchangeSlot.Name => known.Name,
+        // a file for a section contest often carries the state instead
+        ExchangeSlot.Section => known.Section.Length > 0 ? known.Section : known.State,
+        ExchangeSlot.Check => Digits(known.Check),
+        ExchangeSlot.Zone => field.Kind == ExchangeFieldKind.ItuZone
+            ? Digits(known.ItuZone)
+            : Digits(known.CqZone),
+        ExchangeSlot.Exchange1 => known.Exchange1,
+        ExchangeSlot.MiscText => known.MiscText,
+        ExchangeSlot.GridSquare => known.GridSquare,
+        ExchangeSlot.Power => known.Power,
+        ExchangeSlot.Qth => known.State,
+        _ => "",
+    };
+
+    private static string Digits(int value) => value > 0 ? value.ToString() : "";
+
     public void Wipe()
     {
         Entry.Clear();