Analysis: read a rarely-read meter as coarse, not absent; newest rows first

Three things a reported Heizoel page got wrong at once. Its tank is dipped
a few times a year and its burner read every few months, which is exactly
the shape the coverage rules had not been walked through.

"No data" for data that exists. A tank books nothing until the next
dipstick closes the interval, so the stretch after the last dipstick is
covered by no run at all, and a bucket no run covers was reported missing.
The burner, whose run reaches into the window, said "only coarser data" --
the honest answer -- so one card claimed there was nothing while the
coverage panel beside it listed years of data. A bucket that no run covers,
no gap overlaps and no opening balance explains now reports the meter's
resolution when its preceding coverage is within one interval of its own
class: it is not silent, it is read rarely. A meter that does book its own
buckets and stops -- a dead hourly source, a sheet asked about a later
month -- still reads missing.

Auto answering twelve months with one bar. Coarse only means "longer than
a month", so a dipstick taken each autumn straddles a New Year as surely
as a month start: coarsening the chart to years bought nothing and cost
every point. The planning resolution now caps coarse at month when a run
crosses a local year edge, and a series that cannot resolve the natural
size no longer coarsens the whole chart -- it is drawn at that size with
its buckets marked, which the chart and table already explain.

A page contradicting itself. The comparison line above the ranking was fed
the leading measure's matched coverage but worded as if it spoke for the
page, directly above a burner row that did compare. It now names the figure
it is about.

Alongside: the "largest changes" ranking no longer drops a meter whose
change is not comparable. It ranks what can be ranked, then lists the rest
with their values and the reason -- the tank had been vanishing from its
own energy type. And every dated table now reads newest first, as lists
are read; charts stay chronological left to right, and the CSV export
stays ascending for spreadsheets.

A-41 to A-43 in the note record the three rules.

tests/Integration.Tests/MeterPage/MeterDetailServiceTests.cs

@@ -202,13 +202,15 @@ public sealed class MeterDetailServiceTests(TimescaleFixture fx)
         var meter = await box.MeterAsync(type, MeterMode.CumulativeCounter, "kWh");
         var other = await box.TypeAsync();
         await box.TypePriceAsync(type, 0.30, D(2025, 1, 1));
+        await box.TypePriceAsync(type, 0.31, D(2025, 5, 1));
         await box.TypePriceAsync(type, 0.32, D(2025, 7, 1));
         await box.MeterPriceAsync(meter, 0.25, D(2025, 3, 1));
         await box.TypePriceAsync(other, 0.99, D(2025, 3, 1));
         await using (var db = fx.CreateContext())
         {
             db.MeterEvents.Add(new MeterEvent { MeterId = meter, Time = Midnight(2025, 2, 10), EventType = MeterEventType.Note, Notes = "before" });
-            db.MeterEvents.Add(new MeterEvent { MeterId = meter, Time = Midnight(2025, 5, 10), EventType = MeterEventType.Note, Notes = "inside" });
+            db.MeterEvents.Add(new MeterEvent { MeterId = meter, Time = Midnight(2025, 4, 10), EventType = MeterEventType.Note, Notes = "inside" });
+            db.MeterEvents.Add(new MeterEvent { MeterId = meter, Time = Midnight(2025, 5, 10), EventType = MeterEventType.Note, Notes = "later" });
             await db.SaveChangesAsync();
         }
 
@@ -216,16 +218,21 @@ public sealed class MeterDetailServiceTests(TimescaleFixture fx)
         var markers = await service.GetMarkersAsync(
             meter, new RecordRange(Midnight(2025, 3, 1), Midnight(2025, 7, 1)), D(2025, 3, 1), D(2025, 6, 30));
 
-        Assert.Equal("inside", Assert.Single(markers.Events).Notes);
+        // Both lists newest first (A-42): the page draws them as one dated list.
+        Assert.Equal(["later", "inside"], markers.Events.Select(e => e.Notes));
         Assert.False(markers.MoreEvents);
-        var change = Assert.Single(markers.TariffChanges);
-        Assert.Equal((TariffScope.Meter, 0.25), (change.Scope, change.Value));
+        Assert.Equal([D(2025, 5, 1), D(2025, 3, 1)], markers.TariffChanges.Select(t => t.ValidFrom));
+        Assert.Equal((TariffScope.Meter, 0.25), (markers.TariffChanges[1].Scope, markers.TariffChanges[1].Value));
 
-        // The tariff list: the meter's own and its type's (and any global), never another type's.
+        // The tariff list: the meter's own and its type's (and any global), never another type's — newest first
+        // inside each scope, so the price that applies now is at the top (A-42).
         var tariffs = await service.GetTariffsAsync(meter);
         Assert.Contains(tariffs, t => t.Scope == TariffScope.Meter && t.ScopeId == meter);
-        Assert.Equal(2, tariffs.Count(t => t.Scope == TariffScope.EnergyType && t.ScopeId == type));
+        Assert.Equal(3, tariffs.Count(t => t.Scope == TariffScope.EnergyType && t.ScopeId == type));
         Assert.DoesNotContain(tariffs, t => t.Scope == TariffScope.EnergyType && t.ScopeId == other);
+        Assert.Equal(
+            [D(2025, 7, 1), D(2025, 5, 1), D(2025, 1, 1)],
+            tariffs.Where(t => t.Scope == TariffScope.EnergyType && t.ScopeId == type).Select(t => t.ValidFrom));
     }
 
     [Fact]

tests/Integration.Tests/MeterPage/MeterPageLogicTests.cs

@@ -278,4 +278,35 @@ public sealed class MeterPageLogicTests
         Assert.NotNull(MeterProjection.For(MonthSeries(1800, ResolutionClass.Month, start, Now.AddDays(-10)), ytd));
         Assert.Null(MeterProjection.For(MonthSeries(1800, ResolutionClass.Month, start, Now.AddDays(-100)), ytd));
     }
+
+    // -------------------------------------------------------------------------------------------------- markers
+
+    [Fact]
+    public void The_period_markers_are_one_dated_list_newest_first() => In("en", () =>
+    {
+        // A-42: events and price changes are drawn as one list, so they interleave by date instead of running down
+        // twice. On one day the event comes first, then the price that starts with it.
+        DateTimeOffset At(int month, int day) =>
+            new DateTimeOffset(2026, month, day, 12, 0, 0, TimeSpan.Zero).ToUniversalTime();
+
+        var markers = new MeterMarkers(
+            [
+                new EventRow(3, At(5, 20), MeterEventType.Delivery, 2000, null, null, "L", null, null),
+                new EventRow(2, At(3, 4), MeterEventType.Note, null, null, null, null, "new tenant", null),
+            ],
+            MoreEvents: false,
+            [
+                new TariffRow(1, TariffScope.EnergyType, 3, TariffComponent.UnitPrice, 0.9, "EUR/L", D(2026, 3, 4), null),
+                new TariffRow(2, TariffScope.Meter, 7, TariffComponent.UnitPrice, 1.1, "EUR/L", D(2026, 1, 1), null),
+            ]);
+
+        var list = MeterMarkerList.Of(markers, Berlin, "Heizöl");
+
+        Assert.Equal([D(2026, 5, 20), D(2026, 3, 4), D(2026, 3, 4), D(2026, 1, 1)], list.Select(m => m.Day));
+        Assert.Equal("Delivery: 2,000.0 L", list[0].Text);
+        Assert.Equal("Note: new tenant", list[1].Text);           // the event of 4 March …
+        Assert.Contains("Heizöl", list[2].Text, StringComparison.Ordinal);   // … then the type price starting that day
+        Assert.Contains("This meter", list[3].Text, StringComparison.Ordinal);
+        Assert.Empty(MeterMarkerList.Of(MeterMarkers.None, Berlin, "Heizöl"));
+    });
 }