normalize mac address to standard format

normalize_mac.go

package main

import (
	"log"
	"regexp"
	"strings"
)

var macRegex = regexp.MustCompile(`^([0-9A-Fa-f]{2}[:-]?){5}([0-9A-Fa-f]{2})$`)

func main() {
	macs := []string{
		"EC-9B-F3-58-05-BA",
		"a1:3c:b2:58:05:ba",
		"a13cb25805ba",
		"LULZ NOT A MAC"}

	for _, m := range macs {
		s, err := NomalizeMac(m)
		if err != nil {
			log.Printf("%s: %s\n", err, m)
		} else {
			log.Printf("mac ok. original: %s, normalized: %s\n", m, s)
		}
	}
}

func NomalizeMac(mac string) (string, error) {
	r := strings.NewReplacer(":", "", "-", "")
	if macRegex.MatchString(mac) {
		return strings.ToLower(r.Replace(mac)), nil
	}
	return "", ErrInvalidMacAddress
}

type Error string

func (e Error) Error() string { return string(e) }

const ErrInvalidMacAddress = Error("invalid mac address")