Move and batch spots the way N1MM does

Two differences from N1MM in the spot path, both found by reading Packet.cs.

Randomising moved every CW spot. PacketSpot.Randomize moves a spot only when it
is not a dupe, not a self spot, not on a CQ frequency, is on CW and is not
working split, and Packet skips it altogether for a station passed to another
band. Moving a dupe or a split station makes it harder to find, not easier, so
this now leaves the same ones alone. Whether a station has been worked comes
from the log, so AppSession asks it before moving a spot.

Split needed knowing where a station is listening, which is in the comment. Qsx
reads it by N1MM's rules: QSX, UP, DOWN, DN, U or D, the word standing alone or
after a space, a bare number after QSX meaning kilohertz inside the band and
anything else an offset from the spot, an offset over a hundred kilohertz
refused unless it says QSX, DN70 read as a grid square rather than five down,
and a listening frequency outside the band thrown away.

Spots reached the bandmap one at a time, each one redrawing every window that
watches it. N1MM queues them and flushes the queue once a second, which is what
this does now: the filters and the randomiser run over the batch, and the
bandmap takes it in one call and raises one change.

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

README.md

@@ -496,7 +496,13 @@ Three of the filters are worth spelling out:
   call, so `W3LPL` also covers `W3LPL-#`. Nothing is filtered by this.
 - **Randomised frequencies.** Each incoming CW spot is moved thirty or sixty
   hertz either way, which is what N1MM does, so the operator has to find the
-  station by ear. Phone and digital spots are left alone.
+  station by ear. Left where they are: phone and digital spots, stations already
+  worked, stations working split, your own spots, and stations passed to another
+  band — the same list N1MM leaves alone.
+
+Spots wait up to a second before they reach the bandmap, and then go on together.
+N1MM collects them the same way: a skimmer feed sends more spots a minute than
+any window can usefully redraw.
 
 The client speaks telnet properly: it answers the option negotiation instead of
 letting the control bytes turn up in the first lines of text, and it reads the

src/Nonemm.App/AppSession.cs

@@ -33,6 +33,13 @@ public sealed class AppSession : IDisposable
 
     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;
@@ -45,8 +52,13 @@ public sealed class AppSession : IDisposable
         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; }
@@ -466,16 +478,58 @@ public sealed class AppSession : IDisposable
         Changed?.Invoke(this, EventArgs.Empty);
     }
 
-    /// A spot the node sent, kept or dropped by the filters on the telnet
-    /// window.
+    /// A spot the node sent. It waits for the next flush rather than going
+    /// straight onto the bandmap.
     private void TakeSpot(Spot spot)
     {
-        if (!spotFilter.Accepts(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;
             }
-        Bandmap.Add(Settings.RandomizeSpots ? SpotJitter.Shifted(spot, BandPlan, jitter) : spot);
+            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()
     {
@@ -499,6 +553,7 @@ public sealed class AppSession : IDisposable
 
     public void Dispose()
     {
+        spotFlush.Dispose();
         DisposeRadios();
         cluster?.Dispose();
         network?.Dispose();

src/Nonemm.Spotting/Bandmap.cs

@@ -43,6 +43,27 @@ public sealed class Bandmap
         Changed?.Invoke(this, EventArgs.Empty);
     }
 
+    /// A batch of spots in one go, so a busy node redraws the windows once
+    /// rather than once a spot. N1MM collects arriving spots the same way.
+    public void AddRange(IEnumerable<Spot> spots)
+    {
+        int added = 0;
+        lock (guard)
+        {
+            foreach (Spot spot in spots)
+            {
+                string key = Key(spot);
+                this.spots[key] = spot;
+                arrived[key] = clock();
+                added++;
+            }
+        }
+        if (added > 0)
+        {
+            Changed?.Invoke(this, EventArgs.Empty);
+        }
+    }
+
     public void Remove(Callsign call, Band band)
     {
         string key = $"{call.Text}|{band.Name}";

src/Nonemm.Spotting/Qsx.cs

@@ -0,0 +1,66 @@
+using System.Globalization;
+using Nonemm.Core;
+
+namespace Nonemm.Spotting;
+
+/// The frequency a split station is listening on, read out of the spot's
+/// comment. The rules are N1MM's `ParseQSX` and what `Packet` does with what it
+/// returns.
+///
+/// A spotter writes it as `QSX 14205`, `QSX 205`, `UP 2` or `DN 5`. The word
+/// has to start the comment or follow a space, so a callsign or a grid square
+/// that happens to hold the letters is not read as an offset.
+public static class Qsx
+{
+    /// Anything further than this from the spot is not an offset: `UP 2` is two
+    /// kilohertz up, `UP 14205` is somebody writing a frequency after the wrong
+    /// word.
+    private const double FurthestOffsetKilohertz = 100;
+
+    /// Zero when the comment says nothing about split working, or when what it
+    /// says lands outside the band.
+    public static Frequency Parse(string comment, Frequency spot)
+    {
+        string text = comment.ToUpperInvariant();
+        double offset = Offset(text, "QSX")
+            ?? Offset(text, "UP")
+            ?? Negative(Offset(text, "DOWN"))
+            ?? Negative(Offset(text, "DN"))
+            ?? Offset(text, "U")
+            ?? Negative(Offset(text, "D"))
+            ?? 0;
+        bool named = text.Contains("QSX", StringComparison.Ordinal);
+        if (offset == 0 || (!named && Math.Abs(offset) > FurthestOffsetKilohertz))
+        {
+            return Frequency.Zero;
+        }
+
+        double kilohertz = named
+            // a bare number after QSX is kilohertz within the band
+            ? (offset < 1000 ? Math.Floor(spot.Kilohertz / 1000) * 1000 : 0) + offset
+            : spot.Kilohertz + offset;
+        Frequency qsx = Frequency.FromKilohertz(kilohertz);
+        return Bands.ForFrequency(spot) is { } band && band.Contains(qsx) ? qsx : Frequency.Zero;
+    }
+
+    private static double? Negative(double? offset) => offset is null ? null : -offset;
+
+    /// The number after the word, when the word stands on its own and a number
+    /// follows it. `DN70` is a grid square, not five kilohertz down.
+    private static double? Offset(string text, string word)
+    {
+        int at = text.IndexOf(word, StringComparison.Ordinal);
+        if (at < 0 || (at > 0 && text[at - 1] != ' '))
+        {
+            return null;
+        }
+        string[] rest = text[(at + word.Length)..]
+            .Split(' ', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+        if (rest.Length == 0
+            || !double.TryParse(rest[0], NumberStyles.Float, CultureInfo.InvariantCulture, out double value))
+        {
+            return null;
+        }
+        return Math.Abs(value);
+    }
+}

src/Nonemm.Spotting/Spot.cs

@@ -11,5 +11,11 @@ public sealed record Spot(
     string Spotter = "",
     string Comment = "")
 {
+    /// Where the station is listening when it is working split, read out of the
+    /// comment. Zero when it is not.
+    public Frequency Qsx { get; init; }
+
+    public bool IsSplit => Qsx.Hertz > 0;
+
     public Band? Band => Bands.ForFrequency(Frequency);
 }

src/Nonemm.Spotting/SpotJitter.cs

@@ -10,13 +10,23 @@ public static class SpotJitter
 {
     private static readonly int[] Offsets = [-60, -30, 30, 60];
 
-    /// Phone and digital spots are left alone: they are wide enough that thirty
-    /// hertz changes nothing.
-    public static Spot Shifted(Spot spot, BandPlan plan, Random random) =>
-        plan.ModeAt(spot.Frequency) == ModeCategory.Cw
+    /// N1MM moves a spot only when it is on CW, is not a dupe, was not spotted
+    /// here, is not working split, and is not one of its own passed stations.
+    /// Everything else is left where it is: phone and digital are wide enough
+    /// that thirty hertz changes nothing, and moving a station somebody is
+    /// about to work makes it harder to find, not easier.
+    public static Spot Shifted(Spot spot, BandPlan plan, Random random, bool isDupe = false)
+    {
+        bool moves = spot.Source == SpotSource.Cluster
+            && !isDupe
+            && !spot.IsSplit
+            && plan.ModeAt(spot.Frequency) == ModeCategory.Cw
+            && !spot.Comment.Contains("Passed Station", StringComparison.OrdinalIgnoreCase);
+        return moves
             ? spot with
             {
                 Frequency = Frequency.FromHertz(spot.Frequency.Hertz + Offsets[random.Next(Offsets.Length)]),
             }
             : spot;
     }
+}

src/Nonemm.Spotting/SpotLine.cs

@@ -35,13 +35,18 @@ public static class SpotLine
         }
         string[] tail = fields[2..];
         int stamp = LastTimeStamp(tail);
+        Frequency where = Frequency.FromKilohertz(kilohertz);
+        string comment = string.Join(' ', stamp < 0 ? tail : tail[..stamp]).Trim();
         return new Spot(
             Callsign.Parse(fields[1]),
-            Frequency.FromKilohertz(kilohertz),
+            where,
             stamp < 0 ? nowUtc : TimeOf(tail[stamp], nowUtc),
             SpotSource.Cluster,
             spotter,
-            string.Join(' ', stamp < 0 ? tail : tail[..stamp]).Trim());
+            comment)
+        {
+            Qsx = Qsx.Parse(comment, where),
+        };
     }
 
     /// The node writes the spot's time as `1234Z`. It is usually the last word,

tests/Nonemm.Spotting.Tests/QsxTests.cs

@@ -0,0 +1,60 @@
+using Nonemm.Core;
+
+namespace Nonemm.Spotting.Tests;
+
+public class QsxTests
+{
+    private static readonly Frequency Spot = Frequency.FromKilohertz(14_025);
+
+    private static double Kilohertz(string comment) => Qsx.Parse(comment, Spot).Kilohertz;
+
+    [Fact]
+    public void AWholeFrequencyAfterQsxIsTakenAsItIs() =>
+        Assert.Equal(14_205, Kilohertz("QSX 14205"));
+
+    [Fact]
+    public void ABareNumberAfterQsxIsKilohertzInTheBand() =>
+        Assert.Equal(14_205, Kilohertz("QSX 205"));
+
+    [Fact]
+    public void UpAndDownAreOffsetsFromTheSpot()
+    {
+        Assert.Equal(14_027, Kilohertz("UP 2"));
+        Assert.Equal(14_020, Kilohertz("DN 5"));
+        Assert.Equal(14_020, Kilohertz("DOWN 5"));
+    }
+
+    [Fact]
+    public void ACommentThatSaysNothingAboutSplitGivesNothing()
+    {
+        Assert.Equal(0, Kilohertz("CQ TEST"));
+        Assert.Equal(0, Kilohertz(""));
+    }
+
+    [Fact]
+    public void AGridSquareIsNotAnOffset() =>
+        Assert.Equal(0, Kilohertz("TNX QSO DN70"));
+
+    [Fact]
+    public void AWordThatOnlyHoldsTheLettersIsNotAnOffset() =>
+        Assert.Equal(0, Kilohertz("GROUP 5"));
+
+    [Fact]
+    public void ABigNumberAfterAnythingButQsxIsNotAnOffset() =>
+        Assert.Equal(0, Kilohertz("UP 14205"));
+
+    [Fact]
+    public void AListeningFrequencyOutsideTheBandIsDropped() =>
+        Assert.Equal(0, Kilohertz("QSX 7205"));
+
+    [Fact]
+    public void TheSpotLineCarriesTheListeningFrequency()
+    {
+        Spot? spot = SpotLine.Parse(
+            "DX de W3LPL:     14025.0  JA1XYZ       UP 2                   1234Z",
+            new DateTime(2026, 8, 28, 12, 0, 0, DateTimeKind.Utc));
+
+        Assert.Equal(14_027_000, Assert.IsType<Spot>(spot).Qsx.Hertz);
+        Assert.True(spot.IsSplit);
+    }
+}

tests/Nonemm.Spotting.Tests/SpotJitterTests.cs

@@ -4,8 +4,12 @@ namespace Nonemm.Spotting.Tests;
 
 public class SpotJitterTests
 {
-    private static Spot At(double kilohertz) =>
-        new(Callsign.Parse("OM5M"), Frequency.FromKilohertz(kilohertz), DateTime.UtcNow, SpotSource.Cluster);
+    private static Spot At(double kilohertz, SpotSource source = SpotSource.Cluster, string comment = "") =>
+        new(Callsign.Parse("OM5M"), Frequency.FromKilohertz(kilohertz), DateTime.UtcNow, source, "W3LPL", comment);
+
+    private static long Offset(Spot spot, bool isDupe = false) =>
+        SpotJitter.Shifted(spot, BandPlan.Default, new Random(1), isDupe).Frequency.Hertz
+            - spot.Frequency.Hertz;
 
     [Fact]
     public void ACwSpotMovesByThirtyOrSixtyHertz()
@@ -14,15 +18,30 @@ public class SpotJitterTests
         for (int run = 0; run < 20; run++)
         {
             Spot moved = SpotJitter.Shifted(At(14_025), BandPlan.Default, random);
-            long offset = moved.Frequency.Hertz - 14_025_000;
-            Assert.Contains(offset, (long[])[-60, -30, 30, 60]);
+            Assert.Contains(moved.Frequency.Hertz - 14_025_000, (long[])[-60, -30, 30, 60]);
         }
     }
 
     [Fact]
-    public void APhoneSpotIsLeftWhereItIs()
+    public void APhoneSpotIsLeftWhereItIs() => Assert.Equal(0, Offset(At(14_250)));
+
+    [Fact]
+    public void AStationAlreadyWorkedIsLeftWhereItIs() =>
+        Assert.Equal(0, Offset(At(14_025), isDupe: true));
+
+    [Fact]
+    public void AStationWorkingSplitIsLeftWhereItIs()
     {
-        Spot spot = At(14_250);
-        Assert.Equal(spot, SpotJitter.Shifted(spot, BandPlan.Default, new Random(1)));
+        Spot split = At(14_025, comment: "UP 2") with { Qsx = Frequency.FromKilohertz(14_027) };
+
+        Assert.Equal(0, Offset(split));
     }
+
+    [Fact]
+    public void OurOwnSpotIsLeftWhereItIs() =>
+        Assert.Equal(0, Offset(At(14_025, SpotSource.Operator)));
+
+    [Fact]
+    public void AStationPassedToAnotherBandIsLeftWhereItIs() =>
+        Assert.Equal(0, Offset(At(14_025, comment: "Passed Station 21025")));
 }