feat(calendar): EF (1962) temporal cycle temporalEF + EF seasons

8 EF seasons by date boundary (Septuagesima, Passiontide, Time after Epiphany/
Pentecost + shared); major feasts of the Lord; Christ the King = last Sun of
October. ParseRank accepts EF ranks.

1 files changed, 146 insertions, 0 deletions

diff --git a/internal/calendar/temporal_ef.go b/internal/calendar/temporal_ef.go
new file mode 100644
index 0000000..725aac2
--- /dev/null
+++ b/internal/calendar/temporal_ef.go
@@ -0,0 +1,146 @@
+package calendar
+
+import "time"
+
+// Extraordinary Form (1962) season constants. Advent/Christmas/Lent/Easter are
+// shared with the OF; these are EF-specific.
+const (
+	Septuagesima       Season = "septuagesima"
+	Passiontide        Season = "passiontide"
+	TimeAfterEpiphany  Season = "time-after-epiphany"
+	TimeAfterPentecost Season = "time-after-pentecost"
+)
+
+// efChristTheKing is the last Sunday of October (the 1962 date — unlike the OF's
+// last Sunday before Advent).
+func efChristTheKing(year int) time.Time {
+	oct31 := time.Date(year, 10, 31, 0, 0, 0, 0, time.UTC)
+	return oct31.AddDate(0, 0, -int(oct31.Weekday())) // Sunday on/before Oct 31
+}
+
+// efColour is the default (Sunday/ferial) colour of an EF season.
+func efColour(s Season) Colour {
+	switch s {
+	case Advent, Septuagesima, Lent, Passiontide:
+		return Violet
+	case Christmas, Easter_:
+		return White
+	default: // TimeAfterEpiphany, TimeAfterPentecost
+		return Green
+	}
+}
+
+// efSeason returns the 1962 season for date, by chronological date boundaries.
+func efSeason(date time.Time, y int, easter time.Time) Season {
+	adventThis := adventStart(y)
+	christmasThis := time.Date(y, 12, 25, 0, 0, 0, 0, time.UTC)
+	jan6 := time.Date(y, 1, 6, 0, 0, 0, 0, time.UTC)
+	septStart := easter.AddDate(0, 0, -63) // Septuagesima Sunday
+	ashWed := easter.AddDate(0, 0, -46)
+	passionSun := easter.AddDate(0, 0, -14)
+	paschalEnd := easter.AddDate(0, 0, 55) // Saturday after Pentecost; Trinity = +56
+
+	switch {
+	case !date.Before(adventThis) && date.Before(christmasThis):
+		return Advent
+	case !date.Before(christmasThis): // Dec 25..31
+		return Christmas
+	case date.Before(jan6): // Jan 1..5
+		return Christmas
+	case date.Before(septStart): // Epiphany .. before Septuagesima
+		return TimeAfterEpiphany
+	case date.Before(ashWed):
+		return Septuagesima
+	case date.Before(passionSun):
+		return Lent
+	case date.Before(easter):
+		return Passiontide
+	case !date.After(paschalEnd):
+		return Easter_
+	default:
+		return TimeAfterPentecost
+	}
+}
+
+func efCel(season Season, slug string, col Colour, rank Rank, week int) temporalDay {
+	return temporalDay{
+		Season: season, Colour: col, Week: week, Rank: rank,
+		Sunday: false,
+		Cel:    Celebration{Slug: slug, Rank: rank, Colour: col, Layer: "temporal"},
+	}
+}
+
+// temporalEF computes the 1962 temporal identity of date. Season is exact
+// (oracle-validated); ranks/weeks are best-effort for display.
+func temporalEF(date time.Time) temporalDay {
+	date = date.UTC().Truncate(24 * time.Hour)
+	y := date.Year()
+	easter := Easter(y)
+	season := efSeason(date, y, easter)
+	col := efColour(season)
+	sun := date.Weekday() == time.Sunday
+
+	// Major feasts of the Lord (I class): nice titles + colour.
+	switch {
+	case date.Month() == time.December && date.Day() == 25:
+		return efCel(Christmas, "ef-nativity", White, RankClass1, 0)
+	case date.Month() == time.January && date.Day() == 1:
+		return efCel(Christmas, "ef-circumcision", White, RankClass1, 0)
+	case date.Month() == time.January && date.Day() == 6:
+		return efCel(TimeAfterEpiphany, "ef-epiphany", White, RankClass1, 0)
+	case sameDay(date, easter.AddDate(0, 0, -46)):
+		return efCel(Lent, "ef-ash-wednesday", Violet, RankClass1, 0)
+	case sameDay(date, easter.AddDate(0, 0, -14)):
+		return efCel(Passiontide, "ef-passion-sunday", Violet, RankClass1, 1)
+	case sameDay(date, easter.AddDate(0, 0, -7)):
+		return efCel(Passiontide, "ef-palm-sunday", Violet, RankClass1, 2)
+	case sameDay(date, easter):
+		return efCel(Easter_, "ef-easter-sunday", White, RankClass1, 1)
+	case sameDay(date, easter.AddDate(0, 0, 7)):
+		return efCel(Easter_, "ef-low-sunday", White, RankClass1, 2)
+	case sameDay(date, easter.AddDate(0, 0, 39)):
+		return efCel(Easter_, "ef-ascension", White, RankClass1, 0)
+	case sameDay(date, easter.AddDate(0, 0, 49)):
+		return efCel(Easter_, "ef-pentecost", Red, RankClass1, 0)
+	case sameDay(date, easter.AddDate(0, 0, 56)):
+		return efCel(TimeAfterPentecost, "ef-trinity", White, RankClass1, 1)
+	case sameDay(date, easter.AddDate(0, 0, 60)):
+		return efCel(TimeAfterPentecost, "ef-corpus-christi", White, RankClass1, 0)
+	case sameDay(date, easter.AddDate(0, 0, 68)):
+		return efCel(TimeAfterPentecost, "ef-sacred-heart", White, RankClass1, 0)
+	case sameDay(date, efChristTheKing(y)):
+		return efCel(TimeAfterPentecost, "ef-christ-the-king", White, RankClass1, 0)
+	}
+
+	// Sundays vs ferias of the current season.
+	if sun {
+		rank := RankClass2
+		if season == Advent && sameDay(date, adventStart(y)) {
+			rank = RankClass1 // 1st Sunday of Advent
+		}
+		return efCel(season, "ef-"+string(season)+"-sunday", col, rank, efWeek(date, season, y, easter))
+	}
+	rank := RankClass4 // per-annum feria
+	if season == Advent || season == Lent || season == Passiontide || season == Septuagesima {
+		rank = RankClass3 // penitential ferias rank higher
+	}
+	return efCel(season, "ef-"+string(season)+"-feria", col, rank, efWeek(date, season, y, easter))
+}
+
+// efWeek is a best-effort week-within-season number for display (not
+// oracle-checked). Time after Pentecost counts Sundays from Pentecost.
+func efWeek(date time.Time, season Season, y int, easter time.Time) int {
+	switch season {
+	case Advent:
+		return daysBetween(adventStart(y), date)/7 + 1
+	case TimeAfterPentecost:
+		return daysBetween(easter.AddDate(0, 0, 49), date) / 7 // Sundays after Pentecost
+	case Lent:
+		return daysBetween(easter.AddDate(0, 0, -42), date)/7 + 1 // from 1st Sunday of Lent
+	case TimeAfterEpiphany:
+		jan6 := time.Date(y, 1, 6, 0, 0, 0, 0, time.UTC)
+		return daysBetween(jan6, date)/7 + 1
+	default:
+		return 0
+	}
+}