}

func validateRegistration(p *Profile, s string) (string, error) {
	if !norm.NFC.IsNormalString(s) {
		return s, &labelError{s, "V1"}
	}
	for i := 0; i < len(s); {
		v, sz := trie.lookupString(s[i:])
		// Copy bytes not copied so far.
		switch p.simplify(info(v).category()) {
		// TODO: handle the NV8 defined in the Unicode idna data set to allow
		// for strict conformance to IDNA2008.

	// TODO: filter need for normalization in loop below.
	if !norm.NFC.IsNormalString(s) {
		return s, false, &labelError{s, "V1"}
	}
	for i := 0; i < len(s); {
		v, sz := trie.lookupString(s[i:])
		if sz == 0 {
			return s, bidi, runeError(utf8.RuneError)
		}
		bidi = bidi || info(v).isBidi(s[i:])
		// Copy bytes not copied so far.
		switch p.simplify(info(v).category()) {