package utils

// Genre display rendering (faceted plan Batch B / Phase 7): the
// canonically-lowercase genre value is title-cased at DISPLAY time
// only — never in the DB. Canonical home: the filter panel (services),
// templ (templates wraps this), and the TS port in bookshelf.ts all
// share these exact rules.

import (
	"strings"
	"unicode"
)

// genreSmallWords stay lowercase in title-case rendering (except the
// first word of the value).
var genreSmallWords = map[string]bool{
	"a": true, "an": true, "and": true, "of": true, "the": true,
	"in": true, "on": true, "for": true, "to": true, "or": true,
}

// PrettifyGenre renders the canonically-lowercase genre value in title
// case at display time (Batch B transform — never in the DB). Only
// values that are ENTIRELY lowercase get transformed; anything else is
// returned verbatim, protecting user-entered mixed case. Small words
// stay down except in the first position; "&" has no case and passes
// through. "science fiction" → "Science Fiction", "sword & sorcery" →
// "Sword & Sorcery".
func PrettifyGenre(value string) string {
	trimmed := strings.TrimSpace(value)
	if trimmed == "" {
		return ""
	}
	if trimmed != strings.ToLower(trimmed) {
		return trimmed // mixed case = user-authored; display as written
	}
	words := strings.Fields(trimmed)
	out := make([]string, len(words))
	for i, w := range words {
		if i > 0 && genreSmallWords[w] {
			out[i] = w
			continue
		}
		runes := []rune(w)
		out[i] = string(append([]rune{unicode.ToUpper(runes[0])}, runes[1:]...))
	}
	return strings.Join(out, " ")
}