package tools

import "unicode/utf8"

// truncateUTF8 returns s truncated to at most maxBytes, backing off to the last
// complete UTF-8 rune boundary so a multibyte rune (CJK, emoji, …) is never
// split — a byte-boundary cut would hand the LLM invalid UTF-8 / replacement
// chars. Used by the meta tools' input caps.
func truncateUTF8(s string, maxBytes int) string {
	if len(s) <= maxBytes {
		return s
	}
	s = s[:maxBytes]
	for len(s) > 0 && !utf8.ValidString(s) {
		s = s[:len(s)-1]
	}
	return s
}