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:]
}