package matcher

import (
	"encoding/json"
	"fmt"
	"log"
	"net"
	"strconv"
	"sync/atomic"
	"time"

	omd "git.loafle.net/overflow/model/discovery"
	omm "git.loafle.net/overflow/model/meta"
	omu "git.loafle.net/overflow/model/util"
	"git.loafle.net/overflow_scanner/probe/discovery/session"
	"git.loafle.net/overflow_scanner/probe/internal/matcher"
	"git.loafle.net/overflow_scanner/probe/internal/pcap"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
)

func scanV4(discoverySession session.DiscoverySession, targetHost *omd.Host) error {
	ps, err := pcap.RetainScanner(targetHost.Zone)
	if nil != err {
		return fmt.Errorf("Discovery: Cannot retain pcap instance %v", err)
	}
	defer func() {
		go pcap.ReleaseScanner(targetHost.Zone)
	}()

	udpChan := ps.OpenUDP(targetHost.Address)
	defer func() {
		go ps.CloseUDP(targetHost.Address, udpChan)
	}()

	timerStopped := make(chan struct{})
	go func() {
		ports := make(map[int]*omd.Port)

		var delay atomic.Value
		delay.Store(false)
		ticker := time.NewTicker(time.Millisecond * 500)
		for {
			select {
			case packet, ok := <-udpChan:
				if !ok {
					// olog.Logger().Debug("Discovery: udp channel is closed")
					return
				}
				delay.Store(true)
				if p := handlePacketUDP4(discoverySession, targetHost, ports, packet); nil != p {
					discoverySession.AddPort(p)
				}
			case <-ticker.C:
				if false == delay.Load().(bool) {
					ticker.Stop()
					timerStopped <- struct{}{}
					return
				}
				delay.Store(false)
			}
		}
	}()

	if err := sendUDP4(discoverySession, ps, targetHost); nil != err {
		log.Printf("sendUDP4 %v", err)
		return nil
	}

	select {
	case <-timerStopped:
		return nil
	case <-discoverySession.StopChan():
		return nil
	}
}

func sendUDP4(discoverySession session.DiscoverySession, ps pcap.PCapScanner, host *omd.Host) error {
	dp := discoverySession.DiscoverPort()

	ip := net.ParseIP(host.Address)
	if nil == ip {
		return fmt.Errorf("IP(%s) of host is not valid", host.Address)
	}

	matchers := matcher.GetUDPMatchers()

	conn, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.IPv4zero, Port: 0})
	if err != nil {
		return err
	}
	defer func() {
		conn.Close()
	}()

	for _, _matcher := range matchers {
	INNER_LOOP:
		for portNumber := dp.FirstScanRange; portNumber < dp.LastScanRange; portNumber++ {
			if nil != dp.ExcludePorts {
				for _, exPortNumber := range dp.ExcludePorts {
					if portNumber == exPortNumber {
						continue INNER_LOOP
					}
				}
			}

			if !_matcher.IsSend(portNumber) {
				continue INNER_LOOP
			}

			addr := &net.UDPAddr{IP: ip.To4(), Port: portNumber}
			for i := 0; i < _matcher.PacketCount(); i++ {
				p := _matcher.Packet(i)
				if _, err := conn.WriteToUDP(p.Buffer, addr); err != nil {
					log.Print("UDP write error", err)
				}
			}

			timer := time.NewTimer(time.Microsecond * 100)

			select {
			case <-timer.C:
			}
		}
	}

	return nil
}

func handlePacketUDP4(discoverySession session.DiscoverySession, host *omd.Host, ports map[int]*omd.Port, packet gopacket.Packet) *omd.Port {
	ipLayer := packet.Layer(layers.LayerTypeIPv4)

	if ipLayer.(*layers.IPv4).SrcIP.String() == host.Zone.Address {
		return nil
	}

	dp := discoverySession.DiscoverPort()

	if net := packet.NetworkLayer(); net == nil {
	} else if udpLayer := packet.Layer(layers.LayerTypeUDP); udpLayer == nil {
	} else if udp, ok := udpLayer.(*layers.UDP); ok {

		// srcIP := ipLayer.(*layers.IPv4).SrcIP
		port := int(udp.SrcPort)

		if _, ok := ports[port]; ok || !dp.Contains(port) {
			return nil
		}

		p := &omd.Port{
			MetaPortType:   omm.ToMetaPortType(omm.MetaPortTypeEnumUDP),
			PortNumber:     json.Number(strconv.Itoa(port)),
			UDPLayer:       udpLayer,
			DiscoveredDate: omu.NowPtr(),
		}
		p.Host = host
		ports[port] = p

		return p
	}

	return nil
}