package bind

import (
	"crypto/sha1"
	"encoding/hex"
	"strings"
)

// catalogHash returns the unique member label for a catalog zone entry: the
// hex-encoded SHA-1 digest of the member zone name in DNS wire format, per the
// BIND catalog-zone schema (RFC 9432).
func catalogHash(zone string) string {
	sum := sha1.Sum(wireName(zone))
	return hex.EncodeToString(sum[:])
}

// wireName encodes a domain name into uncompressed DNS wire format: each label
// length-prefixed, terminated by a zero-length root label. Names are lowercased.
func wireName(name string) []byte {
	name = strings.TrimSuffix(strings.ToLower(strings.TrimSpace(name)), ".")
	var out []byte
	if name != "" {
		for _, label := range strings.Split(name, ".") {
			out = append(out, byte(len(label)))
			out = append(out, []byte(label)...)
		}
	}
	return append(out, 0)
}