Resynchronize a log with the other stations, and rescore it

A station that was away — a laptop that lost the network, one that was
switched off — comes back missing whatever the others logged while it was
gone. N1MM fills that in by walking the log an hour at a time, and this is
that walk, on the same messages:

| Message | What it says |
|---|---|
| `CHECKSUM` | here is what I hold for your contacts in this hour, and the contest and callsign I am logging |
| `DELETEQS` | drop your copies of my contacts in that hour, I am sending them again |
| `RESYNCQSO` | one of those contacts |
| `CONFIRMED` | here is what the hour hashes to at my end — which also asks for the next hour |

Each station is the authority on the contacts it made, so an hour that
disagrees is replaced rather than merged. The answer to one block asks for
the next, and the walk ends when the block starts after the end of the
period. The Resynchronize tab counts the hours that agreed, the hours that
were sent again and the hours that still disagreed, which are N1MM's
columns.

**`LogChecksum`** is N1MM's: a CRC32 over the `DXLOG` columns of the block,
ordered by time and then callsign, leaving out what each station works out
for itself — points, the three multiplier flags, the country prefix, the
continent, the WPX prefix and `IsOriginal`. Two stations may disagree about
those and still hold the same log. A checksum that disagrees for any other
reason costs one block of traffic, which is what a resync is for.

**The link still holds no log.** It asks one through `ContactLog` for the
contacts of a computer in a block of time, and `SessionContactLog` answers
on the window thread, because that is where the log is touched.

**Every contact logged here now carries the computer that made it.** N1MM
stamps `NetBiosName` and `NetworkedCompNr` on every row and this program
did not, so its own contacts belonged to no station and a resync could not
ask for them.

**Rescore** writes the points and multiplier flags of a period back to the
database. The log in memory scores itself whenever it changes; the stored
rows do not, and N1MM reads them rather than working them out. A contact
that arrives from another station after the one that took a multiplier
leaves those columns behind. A station can also ask the others to rescore
when its resync finishes, which is the flag on the end of `CHECKSUM`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PdAYHcdRktqKry7nk414TU

src/Nonemm.App/AppSession.cs

@@ -219,6 +219,11 @@ public sealed class AppSession : IDisposable
             // 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++)
@@ -283,6 +288,11 @@ public sealed class AppSession : IDisposable
     /// 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();
@@ -293,7 +303,7 @@ public sealed class AppSession : IDisposable
             return;
         }
         link = new StationLink(
-            Settings.NetworkStationName.Length > 0 ? Settings.NetworkStationName : Environment.MachineName,
+            ComputerName,
             Settings.StationLinkVersion,
             Settings.StationNumber,
             Settings.StationLinkPort)
@@ -304,6 +314,11 @@ public sealed class AppSession : IDisposable
         // 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));
         foreach (string peer in Settings.StationLinkPeers)
         {
             if (Peer(peer) is var (name, address, port))
@@ -348,6 +363,12 @@ public sealed class AppSession : IDisposable
         _ = link.SendBandAsync(position.Frequency, position.Mode, position.IsRunning, position.RadioNumber);
     }
 
+    /// 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
@@ -414,6 +435,9 @@ public sealed class AppSession : IDisposable
             case ContactDeleted deleted:
                 Logging.DeleteFromNetwork(deleted.Id, deleted.Call, deleted.TimestampUtc);
                 break;
+            case ContactsCleared cleared:
+                Logging.ClearFromNetwork(cleared.StationName, cleared.FromUtc, cleared.Length);
+                break;
         }
     }