package updateip

import "strings"

// Canonicalize a DNS record.
func Canonicalize(domainName, recordName string) string {
	if recordName == "@" {
		return ToFqdn(domainName)
	} else if strings.HasSuffix(recordName, ".@") {
		return ToFqdn(strings.TrimSuffix(recordName, "@") + domainName)
	}
	return ToFqdn(recordName)
}

// IsFqdn checks if the label is a full-qualified name.
func IsFqdn(name string) bool {
	return strings.HasSuffix(name, ".")
}

// ToFqdn converts the name into a fqdn appending a trailing dot.
func ToFqdn(name string) string {
	if name == "@" {
		return name
	}
	n := len(name)
	if n == 0 || name[n-1] == '.' {
		return name
	}
	return name + "."
}

// UnFqdn converts the fqdn into a name removing the trailing dot.
func UnFqdn(name string) string {
	n := len(name)
	if n != 0 && name[n-1] == '.' {
		return name[:n-1]
	}
	return name
}