package service

import (
	"bytes"
	"encoding/hex"
	"errors"
	"net"

	"src.dualinventive.com/go/dinet/rpc"
)

// getMacAddr gets the MAC hardware address of the host machine
func getMacAddr() (string, error) {
	interfaces, err := net.Interfaces()
	if err == nil {
		for _, i := range interfaces {
			if i.Flags&(net.FlagUp|net.FlagLoopback) == net.FlagUp && !bytes.Equal(i.HardwareAddr, nil) {
				return hex.EncodeToString([]byte(i.HardwareAddr)), nil
			}
		}
	}
	return "", errors.New("no MAC address found")
}

// GenerateUIDFromMac generates a device UID based on the MAC address of the host machine
func GenerateUIDFromMac(prefix string) (string, error) {
	mac, err := getMacAddr()
	if err != nil {
		return rpc.DeviceUIDInvalid, err
	}
	return rpc.GenerateDeviceUID(prefix, mac)
}