Merge branch 'engine-precedence-fixes': OF/EF calendar+readings flawlessness pass

Per-day validation vs litcal (OF) and missalemeum (EF) 2005-2050, all defects
fixed and re-validated to zero: OF calendar 0 real errors forward, OF readings
0 unresolvable, EF 0 reading gaps + resumed Sundays correct.

1 files changed, 32 insertions, 0 deletions

diff --git a/internal/calendar/calendar.go b/internal/calendar/calendar.go
index d224e87..33706d8 100644
--- a/internal/calendar/calendar.go
+++ b/internal/calendar/calendar.go
@@ -18,6 +18,19 @@ func Compute(date time.Time, sel Selection, layers []Layer) LiturgicalDay {
 	return computeOF(date, sel, layers)
 }
 
+// TemporalSlug returns the slug of date's TEMPORAL day (the season's Sunday or
+// feria), ignoring any sanctoral celebration that outranks it. The EF's
+// green-season weekday-repeats-the-Sunday rule uses this so a Monday still finds
+// its Sunday Mass even when that Sunday was displaced by a feast (e.g. the
+// Purification on Feb 2).
+func TemporalSlug(date time.Time, sel Selection) string {
+	date = date.UTC().Truncate(24 * time.Hour)
+	if sel.Form == "old" {
+		return temporalEF(date).Cel.Slug
+	}
+	return temporal(date, sel).Cel.Slug
+}
+
 // computeEF computes the Extraordinary Form (1962) day.
 func computeEF(date time.Time, sel Selection, layers []Layer) LiturgicalDay {
 	td := temporalEF(date)
@@ -145,10 +158,29 @@ func movableMemorialsOF(y int) []movableCel {
 
 // transferIfImpeded moves a solemnity off a band-1/2 temporal day to the next
 // free day. Non-solemnities are never transferred (they yield instead).
+//
+// Two impeded solemnities are ANTICIPATED (moved earlier) rather than deferred,
+// matching the General Roman Calendar's published transfers:
+//   - St Joseph (Mar 19) falling in Holy Week goes to the Saturday before Palm
+//     Sunday. (The Annunciation, by contrast, defers past the octave via the
+//     generic forward walk below -- to the Monday after the 2nd Sunday of Easter.)
+//   - The Nativity of St John the Baptist (Jun 24), when the day is a solemnity
+//     of the Lord (the Sacred Heart or Corpus Christi falling on Jun 24), goes
+//     to Jun 23.
 func transferIfImpeded(cel Celebration, when time.Time, sel Selection) time.Time {
 	if cel.Rank != RankSolemnity {
 		return when
 	}
+	if strings.Contains(cel.Slug, "joseph-husband") {
+		if palm := Easter(when.Year()).AddDate(0, 0, -7); !when.Before(palm) {
+			return palm.AddDate(0, 0, -1) // Holy Week -> Saturday before Palm Sunday
+		}
+	}
+	if strings.Contains(cel.Slug, "john-the-baptist") {
+		if td := temporal(when, sel); td.Cel.Rank == RankSolemnity && td.Class == ClassLord && !td.Sunday {
+			return when.AddDate(0, 0, -1) // Sacred Heart / Corpus Christi on Jun 24 -> Jun 23
+		}
+	}
 	day := when
 	for i := 0; i < 30; i++ {
 		b := temporal(day, sel)