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/Windows/NetworkStatusWindow.axaml.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using Avalonia.Controls;
 using Avalonia.Interactivity;
 using Avalonia.Threading;
@@ -15,10 +16,9 @@ namespace Nonemm.App.Windows;
 /// operator reads its own station number and the version it is claiming off the
 /// same window as everybody else's.
 ///
-/// Three of N1MM's tabs are here. Resynchronize, Rescore and the transmit
-/// interlocks of its Options tab are not: this program has neither the resync
-/// messages nor a transmit interlock, and a tab of controls that do nothing is
-/// worse than no tab.
+/// Five of N1MM's tabs are here. Its Options tab and its call-stacking target
+/// tab are not: the transmit interlocks behind Options are not written, and a
+/// tab of controls that do nothing is worse than no tab.
 ///
 /// The window redraws once a second and on every message, which on a busy
 /// network is several a second. That is what a status window is for, and the
@@ -33,6 +33,9 @@ public sealed partial class NetworkStatusWindow : RefreshableWindow
     private readonly Dictionary<string, TimeSpan> echoes = new(StringComparer.OrdinalIgnoreCase);
     private readonly DispatcherTimer clock;
     private StationLink? link;
+    /// Set while a resync that was asked to rescore when it finishes is
+    /// running. It holds the start of the period, which is what gets rescored.
+    private DateTime? rescoreAfterResync;
 
     public NetworkStatusWindow(AppSession session)
     {
@@ -45,6 +48,12 @@ public sealed partial class NetworkStatusWindow : RefreshableWindow
                 e.Row.Foreground = row.Colour;
             }
         };
+        // the two Since boxes start at the contest, which is the period an
+        // operator asks for most often
+        string start = (session.Logging?.Instance.StartDate ?? DateTime.UtcNow)
+            .ToString("yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);
+        ResyncSinceBox.Text = start;
+        RescoreSinceBox.Text = start;
         Attach();
         // the Receive column is a countdown, so it has to redraw with nothing
         // arriving
@@ -81,6 +90,8 @@ public sealed partial class NetworkStatusWindow : RefreshableWindow
         Rows.ItemsSource = rows;
         Rows.SelectedItem = rows.FirstOrDefault(r =>
             string.Equals(r.Station.ComputerName, selected, StringComparison.OrdinalIgnoreCase));
+        ResyncRows.ItemsSource = rows.Where(r => !r.Station.IsMine).ToList();
+        RescoreWhenResyncDone();
         ReportEchoes();
         StateText.Text = State();
         ShowMessages();
@@ -191,6 +202,96 @@ public sealed partial class NetworkStatusWindow : RefreshableWindow
         MessageScroll.ScrollToEnd();
     }
 
+    /// The rescore an operator asked for when the resync is done, once every
+    /// station has stopped.
+    private void RescoreWhenResyncDone()
+    {
+        if (rescoreAfterResync is not { } from
+            || link is null
+            || link.Stations.Any(s => s.IsResyncing))
+        {
+            return;
+        }
+        rescoreAfterResync = null;
+        Say($"rescored {session.Rescore(from)} contacts");
+    }
+
+    /// The start of the period the resync and rescore buttons work on.
+    /// `Since` reads the box, which is a time of day in UTC the way the rest of
+    /// the program writes one.
+    private DateTime? Since(TextBox box)
+    {
+        if (DateTime.TryParseExact(
+            (box.Text ?? "").Trim(),
+            ["yyyy-MM-dd HH:mm", "yyyy-MM-dd HH:mm:ss", "yyyy-MM-dd"],
+            CultureInfo.InvariantCulture,
+            DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal,
+            out DateTime when))
+        {
+            return when;
+        }
+        Say($"{box.Text} is not a time — write it as 2026-09-03 14:00");
+        return null;
+    }
+
+    private static DateTime HoursAgo(TextBox box) =>
+        DateTime.UtcNow.AddHours(-Math.Max(1, int.TryParse((box.Text ?? "").Trim(), out int hours) ? hours : 4));
+
+    /// The whole contest, from three hours before it started. N1MM allows the
+    /// same margin either side, for a clock that is out and for the contacts
+    /// entered after the contest ended.
+    private DateTime ContestStart() =>
+        (session.Logging?.Instance.StartDate ?? DateTime.UtcNow.AddDays(-1)).AddHours(-3);
+
+    private void OnResyncContest(object? sender, RoutedEventArgs e) => Resync(ContestStart());
+
+    private void OnResyncSince(object? sender, RoutedEventArgs e)
+    {
+        if (Since(ResyncSinceBox) is { } from)
+        {
+            Resync(from);
+        }
+    }
+
+    private void OnResyncLast(object? sender, RoutedEventArgs e) => Resync(HoursAgo(ResyncHoursBox));
+
+    /// Asks every connected station whether it and this one hold the same
+    /// contacts, an hour at a time, from `fromUtc` until now.
+    private void Resync(DateTime fromUtc)
+    {
+        if (link is null)
+        {
+            return;
+        }
+        bool everyStation = ResyncAllBox.IsChecked == true;
+        bool rescore = RescoreWhenDoneBox.IsChecked == true;
+        rescoreAfterResync = rescore ? fromUtc : null;
+        link.StartResyncAll(fromUtc, DateTime.UtcNow, everyStation, rescore);
+        Say($"resync from {fromUtc:yyyy-MM-dd HH:mm}Z");
+        Tabs.SelectedIndex = 2;
+    }
+
+    private void OnRescoreContest(object? sender, RoutedEventArgs e) => Rescore(DateTime.MinValue);
+
+    private void OnRescoreSince(object? sender, RoutedEventArgs e)
+    {
+        if (Since(RescoreSinceBox) is { } from)
+        {
+            Rescore(from);
+        }
+    }
+
+    private void OnRescoreLast(object? sender, RoutedEventArgs e) => Rescore(HoursAgo(RescoreHoursBox));
+
+    /// Scores the log again and writes the points and multiplier flags back.
+    /// Nothing is sent: the other stations score their own logs.
+    private void Rescore(DateTime fromUtc)
+    {
+        int written = session.Rescore(fromUtc);
+        RescoreText.Text = $"wrote {written} contacts at {DateTime.UtcNow:HH:mm:ss}Z";
+        Say($"rescored {written} contacts");
+    }
+
     /// The station the operator right-clicked, or null when the row is this
     /// computer's own: nothing in the menu is worth doing to yourself.
     private NetworkedStation? Chosen() =>
@@ -216,7 +317,7 @@ public sealed partial class NetworkStatusWindow : RefreshableWindow
         TalkBox.Focus();
     }
 
-    private void OnShowMessages(object? sender, RoutedEventArgs e) => Tabs.SelectedIndex = 2;
+    private void OnShowMessages(object? sender, RoutedEventArgs e) => Tabs.SelectedIndex = 4;
 
     private async void OnEcho(object? sender, RoutedEventArgs e)
     {