feat(calendar): precedenceEF (1960 occurrence by class + temporal-before-sanctoral)

1 files changed, 49 insertions, 0 deletions

diff --git a/internal/calendar/precedence_ef.go b/internal/calendar/precedence_ef.go
new file mode 100644
index 0000000..81862b7
--- /dev/null
+++ b/internal/calendar/precedence_ef.go
@@ -0,0 +1,49 @@
+package calendar
+
+import "sort"
+
+// efRankOrder orders EF (1960) ranks: class-1 highest, then class-2..4,
+// commemoration, ferial lowest.
+func efRankOrder(r Rank) int {
+	switch r {
+	case RankClass1:
+		return 5
+	case RankClass2:
+		return 4
+	case RankClass3:
+		return 3
+	case RankClass4:
+		return 2
+	case RankCommemoration:
+		return 1
+	default: // ferial / unset
+		return 0
+	}
+}
+
+// precedenceEF ranks an EF candidate for occurrence (lower = higher precedence):
+// by class first, then — at equal class — the temporal office before the
+// sanctoral (a first-cut of the 1960 occurrence table; the missalemeum oracle
+// drives refinement).
+func precedenceEF(c candidate) int {
+	p := (6 - efRankOrder(c.Cel.Rank)) * 2 // class-1 -> 2, ferial -> 12
+	if !c.Temporal {
+		p++ // sanctoral yields to a temporal office of equal class
+	}
+	return p
+}
+
+// pickEF returns the observed EF celebration and the commemorations, ordered
+// deterministically by precedence then slug.
+func pickEF(cands []candidate) (candidate, []candidate) {
+	sorted := make([]candidate, len(cands))
+	copy(sorted, cands)
+	sort.SliceStable(sorted, func(i, j int) bool {
+		pi, pj := precedenceEF(sorted[i]), precedenceEF(sorted[j])
+		if pi != pj {
+			return pi < pj
+		}
+		return sorted[i].Cel.Slug < sorted[j].Cel.Slug
+	})
+	return sorted[0], sorted[1:]
+}