package arp

import (
	"net"
	"sync"
	"time"

	"github.com/sirupsen/logrus"
)

func init() {
	go func() {
		t := time.NewTicker(time.Second * 5)
		for {
			refresh()
			<-t.C
		}
	}()
}

var table sync.Map

func refresh() {
	t, err := lookup()
	if err != nil {
		logrus.StandardLogger().WithError(err).Warn("arp cache refresh failed")
	} else {
		for k, v := range t {
			logrus.StandardLogger().WithFields(logrus.Fields{
				"mac": v,
				"ip":  k,
			}).Debug("Updating ARP cache")
			table.Store(k, v)
		}
	}
}

func Get(addr net.Addr) net.HardwareAddr {
	if addr == nil {
		logrus.StandardLogger().Trace("No address found, can't lookup IP for MAC")
		return nil
	}

	var ip net.IP
	switch addr := addr.(type) {
	case *net.TCPAddr:
		ip = addr.IP
	case *net.UDPAddr:
		ip = addr.IP
	}
	if ip == nil {
		logrus.StandardLogger().WithField("addr", addr.String()).Trace("No IP address found, can't lookup MAC")
		return nil
	}

	if v, ok := table.Load(ip.String()); ok {
		logrus.StandardLogger().WithField("ip", ip.String()).Tracef("%s is at %s", ip, v.(net.HardwareAddr).String())
		return v.(net.HardwareAddr)
	}

	logrus.StandardLogger().WithField("ip", ip.String()).Trace("No MAC address found")
	return nil
}