func convertToPort(v string) (uint32, error) {
	p, err := strconv.ParseUint(v, 10, 32)
	if err != nil || p > 65535 {
		return 0, fmt.Errorf("invalid port %s: %v", v, err)
	}
	return uint32(p), nil
}

func extractNameInBrackets(s string) (string, error) {
	if !strings.HasPrefix(s, "[") || !strings.HasSuffix(s, "]") {
		return "", fmt.Errorf("expecting format [<NAME>], but found %s", s)
	}

}

func (requestHeaderGenerator) principal(key, value string, forTCP bool, _ bool) (*rbacpb.Principal, error) {
	if forTCP {
		return nil, fmt.Errorf("%q is HTTP only", key)
	}

	header, err := extractNameInBrackets(strings.TrimPrefix(key, attrRequestHeader))
	if err != nil {
		return nil, err
	}
	m := matcher.HeaderMatcher(header, value)
	return principalHeader(m), nil
}

type requestClaimGenerator struct{}