package modules

import (
	"fmt"
	"net"
	"sync"
	"time"

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

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/google/gopacket/pcap"
)

var maxStationTTL = 5 * time.Minute

type WiFiProbe struct {
	FromAddr   net.HardwareAddr
	FromVendor string
	FromAlias  string
	SSID       string
	RSSI       int8
}

type WiFiModule struct {
	session.SessionModule

	handle              *pcap.Handle
	source              string
	channel             int
	hopPeriod           time.Duration
	frequencies         []int
	ap                  *network.AccessPoint
	stickChan           int
	skipBroken          bool
	pktSourceChan       chan gopacket.Packet
	pktSourceChanClosed bool
	writes              *sync.WaitGroup
	reads               *sync.WaitGroup
}

func NewWiFiModule(s *session.Session) *WiFiModule {
	w := &WiFiModule{
		SessionModule: session.NewSessionModule("wifi.recon", s),
		channel:       0,
		stickChan:     0,
		hopPeriod:     250 * time.Millisecond,
		ap:            nil,
		skipBroken:    true,
		writes:        &sync.WaitGroup{},
		reads:         &sync.WaitGroup{},
	}

	w.AddHandler(session.NewModuleHandler("wifi.recon on", "",
		"Start 802.11 wireless base stations discovery.",
		func(args []string) error {
			return w.Start()
		}))

	w.AddHandler(session.NewModuleHandler("wifi.recon off", "",
		"Stop 802.11 wireless base stations discovery.",
		func(args []string) error {
			return w.Stop()
		}))

	w.AddHandler(session.NewModuleHandler("wifi.recon MAC", "wifi.recon ((?:[0-9A-Fa-f]{2}[:-]){5}(?:[0-9A-Fa-f]{2}))",
		"Set 802.11 base station address to filter for.",
		func(args []string) error {
			bssid, err := net.ParseMAC(args[0])
			if err != nil {
				return err
			} else if ap, found := w.Session.WiFi.Get(bssid.String()); found == true {
				w.ap = ap
				w.stickChan = network.Dot11Freq2Chan(ap.Frequency)
				return nil
			}
			return fmt.Errorf("Could not find station with BSSID %s", args[0])
		}))

	w.AddHandler(session.NewModuleHandler("wifi.recon clear", "",
		"Remove the 802.11 base station filter.",
		func(args []string) error {
			w.ap = nil
			w.stickChan = 0
			return nil
		}))

	w.AddHandler(session.NewModuleHandler("wifi.deauth BSSID", `wifi\.deauth ((?:[0-9A-Fa-f]{2}[:-]){5}(?:[0-9A-Fa-f]{2}))`,
		"Start a 802.11 deauth attack, if an access point BSSID is provided, every client will be deauthenticated, otherwise only the selected client.",
		func(args []string) error {
			bssid, err := net.ParseMAC(args[0])
			if err != nil {
				return err
			}
			return w.startDeauth(bssid)
		}))

	w.AddHandler(session.NewModuleHandler("wifi.show", "",
		"Show current wireless stations list (default sorting by essid).",
		func(args []string) error {
			return w.Show("rssi")
		}))

	w.AddParam(session.NewIntParameter("wifi.recon.channel",
		"",
		"WiFi channel or empty for channel hopping."))

	w.AddParam(session.NewStringParameter("wifi.source.file",
		"",
		"",
		"If set, the wifi module will read from this pcap file instead of the hardware interface."))

	w.AddParam(session.NewIntParameter("wifi.hop.period",
		"250",
		"If channel hopping is enabled (empty wifi.recon.channel), this is the time in millseconds the algorithm will hop on every channel (it'll be doubled if both 2.4 and 5.0 bands are available)."))

	w.AddParam(session.NewBoolParameter("wifi.skip-broken",
		"true",
		"If true, dot11 packets with an invalid checksum will be skipped."))

	return w
}

func (w WiFiModule) Name() string {
	return "wifi.recon"
}

func (w WiFiModule) Description() string {
	return "A module to monitor and perform wireless attacks on 802.11."
}

func (w WiFiModule) Author() string {
	return "Gianluca Braga <matrix86@protonmail.com> && Simone Margaritelli <evilsocket@protonmail.com>>"
}

func (w *WiFiModule) Configure() error {
	var hopPeriod int
	var err error

	if err, w.source = w.StringParam("wifi.source.file"); err != nil {
		return err
	}

	if w.source != "" {
		if w.handle, err = pcap.OpenOffline(w.source); err != nil {
			return err
		}
	} else {
		ihandle, err := pcap.NewInactiveHandle(w.Session.Interface.Name())
		if err != nil {
			return err
		}
		defer ihandle.CleanUp()

		if err = ihandle.SetRFMon(true); err != nil {
			return fmt.Errorf("Error while setting interface %s in monitor mode: %s", core.Bold(w.Session.Interface.Name()), err)
		} else if err = ihandle.SetSnapLen(65536); err != nil {
			return err
		} else if err = ihandle.SetTimeout(pcap.BlockForever); err != nil {
			return err
		} else if w.handle, err = ihandle.Activate(); err != nil {
			return err
		}
	}

	if err, w.skipBroken = w.BoolParam("wifi.skip-broken"); err != nil {
		return err
	} else if err, hopPeriod = w.IntParam("wifi.hop.period"); err != nil {
		return err
	}

	w.hopPeriod = time.Duration(hopPeriod) * time.Millisecond

	if w.source == "" {
		if err, w.channel = w.IntParam("wifi.recon.channel"); err == nil {
			if err = network.SetInterfaceChannel(w.Session.Interface.Name(), w.channel); err != nil {
				return err
			}
			log.Info("WiFi recon active on channel %d.", w.channel)
		} else {
			w.channel = 0
			// we need to start somewhere, this is just to check if
			// this OS supports switching channel programmatically.
			if err = network.SetInterfaceChannel(w.Session.Interface.Name(), 1); err != nil {
				return err
			}
			log.Info("WiFi recon active with channel hopping.")
		}

		if frequencies, err := network.GetSupportedFrequencies(w.Session.Interface.Name()); err != nil {
			return err
		} else {
			w.frequencies = frequencies
		}
	}

	return nil
}

func (w *WiFiModule) discoverAccessPoints(radiotap *layers.RadioTap, dot11 *layers.Dot11, packet gopacket.Packet) {
	// search for Dot11InformationElementIDSSID
	if ok, ssid := packets.Dot11ParseIDSSID(packet); ok == true {
		from := dot11.Address3
		if network.IsZeroMac(from) == false && network.IsBroadcastMac(from) == false {
			bssid := from.String()
			frequency := int(radiotap.ChannelFrequency)
			w.Session.WiFi.AddIfNew(ssid, bssid, frequency, radiotap.DBMAntennaSignal)
		}
	}
}

func (w *WiFiModule) discoverProbes(radiotap *layers.RadioTap, dot11 *layers.Dot11, packet gopacket.Packet) {
	if dot11.Type != layers.Dot11TypeMgmtProbeReq {
		return
	}

	reqLayer := packet.Layer(layers.LayerTypeDot11MgmtProbeReq)
	if reqLayer == nil {
		return
	}

	req, ok := reqLayer.(*layers.Dot11MgmtProbeReq)
	if ok == false {
		return
	}

	tot := len(req.Contents)
	if tot < 3 {
		return
	}

	avail := uint32(tot - 2)
	if avail < 2 {
		return
	}
	size := uint32(req.Contents[1])
	if size == 0 || size > avail {
		return
	}

	w.Session.Events.Add("wifi.client.probe", WiFiProbe{
		FromAddr:   dot11.Address2,
		FromVendor: network.OuiLookup(dot11.Address2.String()),
		FromAlias:  w.Session.Lan.GetAlias(dot11.Address2.String()),
		SSID:       string(req.Contents[2 : 2+size]),
		RSSI:       radiotap.DBMAntennaSignal,
	})
}

func (w *WiFiModule) discoverClients(radiotap *layers.RadioTap, dot11 *layers.Dot11, packet gopacket.Packet) {
	w.Session.WiFi.EachAccessPoint(func(bssid string, ap *network.AccessPoint) {
		// packet going to this specific BSSID?
		if packets.Dot11IsDataFor(dot11, ap.HW) == true {
			ap.AddClient(dot11.Address2.String(), int(radiotap.ChannelFrequency), radiotap.DBMAntennaSignal)
		}
	})
}

func (w *WiFiModule) updateStats(dot11 *layers.Dot11, packet gopacket.Packet) {
	// collect stats from data frames
	if dot11.Type.MainType() == layers.Dot11TypeData {
		bytes := uint64(len(packet.Data()))

		dst := dot11.Address1.String()
		if station, found := w.Session.WiFi.Get(dst); found == true {
			station.Received += bytes
		}

		src := dot11.Address2.String()
		if station, found := w.Session.WiFi.Get(src); found == true {
			station.Sent += bytes
		}
	}

	if ok, enc, cipher, auth := packets.Dot11ParseEncryption(packet, dot11); ok == true {
		bssid := dot11.Address3.String()
		if station, found := w.Session.WiFi.Get(bssid); found == true {
			station.Encryption = enc
			station.Cipher = cipher
			station.Authentication = auth
		}
	}
}

func (w *WiFiModule) stationPruner() {
	w.reads.Add(1)
	defer w.reads.Done()

	log.Debug("WiFi stations pruner started.")
	for w.Running() == true {
		for _, s := range w.Session.WiFi.List() {
			sinceLastSeen := time.Since(s.LastSeen)
			if sinceLastSeen > maxStationTTL {
				log.Debug("Station %s not seen in %s, removing.", s.BSSID(), sinceLastSeen)
				w.Session.WiFi.Remove(s.BSSID())
			}
		}
		time.Sleep(1 * time.Second)
	}
}

func (w *WiFiModule) trackPacket(pkt gopacket.Packet) {
	pktSize := uint64(len(pkt.Data()))

	w.Session.Queue.Stats.Lock()

	w.Session.Queue.Stats.PktReceived++
	w.Session.Queue.Stats.Received += pktSize

	w.Session.Queue.Stats.Unlock()
}

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

	w.SetRunning(true, func() {
		// start channel hopper if needed
		if w.channel == 0 && w.source == "" {
			go w.channelHopper()
		}

		// start the pruner
		go w.stationPruner()

		w.reads.Add(1)
		defer w.reads.Done()

		src := gopacket.NewPacketSource(w.handle, w.handle.LinkType())
		w.pktSourceChan = src.Packets()
		for packet := range w.pktSourceChan {
			if w.Running() == false {
				break
			}

			if packet == nil {
				continue
			}

			w.trackPacket(packet)

			// perform initial dot11 parsing and layers validation
			if ok, radiotap, dot11 := packets.Dot11Parse(packet); ok == true {
				// check FCS checksum
				if w.skipBroken && dot11.ChecksumValid() == false {
					log.Debug("Skipping dot11 packet with invalid checksum.")
					continue
				}

				w.discoverProbes(radiotap, dot11, packet)
				w.discoverAccessPoints(radiotap, dot11, packet)
				w.discoverClients(radiotap, dot11, packet)
				w.updateStats(dot11, packet)
			}
		}
		w.pktSourceChanClosed = true
	})

	return nil
}

func (w *WiFiModule) Stop() error {
	return w.SetRunning(false, func() {
		// wait any pending write operation
		w.writes.Wait()
		// signal the main for loop we want to exit
		if w.pktSourceChanClosed == false {
			w.pktSourceChan <- nil
		}
		// close the pcap handle to make the main for exit
		w.handle.Close()
		// close the pcap handle to make the main for exit
		// wait for the loop to exit.
		w.reads.Wait()
	})
}