1 files changed, 49 insertions, 0 deletions
diff --git a/internal/caldata/readings.go b/internal/caldata/readings.go
index d082e26..2b3b5af 100644
--- a/internal/caldata/readings.go
+++ b/internal/caldata/readings.go
@@ -66,6 +66,9 @@ func Readings(sel calendar.Selection, layers []calendar.Layer, date time.Time, d
 		if r := efEpiphanytideOpeningReadings(day); len(r) > 0 {
 			return r
 		}
+		if r := efEpiphanyWeekReadings(day); len(r) > 0 {
+			return r
+		}
 		if r := TemporalReadings("old", day.Observed.Slug); len(r) > 0 {
 			return r
 		}
@@ -222,3 +225,49 @@ func efEpiphanytideOpeningReadings(day calendar.LiturgicalDay) []calendar.Readin
 		{Part: "gospel", Citation: "Luke 2:21"},
 	}
 }
+
+// efEpiphanyWeekReadings returns the Mass of a FERIAL day between Epiphany and
+// the first Sunday after it.
+//
+// Those days repeat the Epiphany's own Mass, Isa 60:1-6 / Matt 2:1-12. The
+// ferias AFTER that Sunday take the Sunday's Mass instead (Rom 12:1-5 /
+// Luke 2:42-52), which is what the walk-back already gives them correctly.
+//
+// lectio cannot tell the two groups apart by slug: both are
+// ef-time-after-epiphany-1-<weekday>, because the week numbering starts at the
+// Sunday and the days before it fall in the same numbered week. So the split
+// is made here, on the date, against the same anchor efWeek uses.
+//
+// Saturdays are excluded by the BVM check running before this one -- an
+// unoccupied Saturday in the window carries Our Lady's office and her Mass.
+// colitur reaches the same result by listing only the five non-Saturday
+// weekdays in its own table.
+func efEpiphanyWeekReadings(day calendar.LiturgicalDay) []calendar.Reading {
+	if day.Date.Month() != time.January || day.Date.Day() < 7 {
+		return nil
+	}
+	if !day.Date.Before(firstSundayAfterEpiphanyForReadings(day.Date.Year())) {
+		return nil
+	}
+	if !strings.HasPrefix(day.Observed.Slug, "ef-") || day.Weekday == time.Sunday {
+		return nil
+	}
+	if !strings.Contains(day.Observed.Slug, "-epiphany-") && !strings.Contains(day.Observed.Slug, "-christmas-") {
+		return nil
+	}
+	return []calendar.Reading{
+		{Part: "first", Citation: "Isa 60:1-6"},
+		{Part: "gospel", Citation: "Matt 2:1-12"},
+	}
+}
+
+// firstSundayAfterEpiphanyForReadings mirrors calendar's own anchor. Duplicated
+// rather than exported because the two packages are separate and one date
+// helper is a smaller cost than widening an API for it.
+func firstSundayAfterEpiphanyForReadings(y int) time.Time {
+	d := time.Date(y, time.January, 7, 0, 0, 0, 0, time.UTC)
+	for d.Weekday() != time.Sunday {
+		d = d.AddDate(0, 0, 1)
+	}
+	return d
+}