package discovery

import (
	"bytes"
	"fmt"
	"net"
	"time"

	"git.loafle.net/commons_go/logging"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"

	"git.loafle.net/overflow/overflow_discovery/api/module/discovery/model"
	"git.loafle.net/overflow/overflow_discovery/commons/pcap"
)

func scanHost(zone *model.Zone, dh *model.DiscoveryHost, resultChan chan interface{}, errChan chan error, doneChan chan<- struct{}) {
	ps, err := pcap.RetainScanner(zone)
	if nil != err {
		errChan <- fmt.Errorf("Discovery: Cannot retain pcap instance %v", err)
		// doneChan <- struct{}{}
		return
	}

	arpChan := ps.OpenARP()
	defer func() {
		if nil != ps {
			ps.CloseARP(arpChan)
			pcap.ReleaseScanner(zone)
		}
		doneChan <- struct{}{}
	}()

	go func() {
		for {
			select {
			case packet, ok := <-arpChan:
				if !ok {
					logging.Logger().Debug(fmt.Sprintf("Discovery: arp channel is closed"))
					return
				}
				logging.Logger().Debug(fmt.Sprintf("Discovery: arp packet %v", packet))
			}
		}
	}()

	time.Sleep(10 * time.Second)
}

func sendARP(ps pcap.PCapScanner, zone *model.Zone, dh *model.DiscoveryHost) error {
	hwAddr, err := net.ParseMAC(zone.Mac)
	if nil != err {
		return err
	}
	ip := net.ParseIP(zone.IP)
	if nil != ip {
		return fmt.Errorf("Discovery: IP(%s) of zone is not valid", zone.IP)
	}

	ranges, err := getTargetHostRange(zone, dh)
	if nil != err {
		return err
	}

	ethPacket := makePacketEthernet(hwAddr)
	arpPacket := makePacketARP(hwAddr, ip)
	opts := gopacket.SerializeOptions{FixLengths: true, ComputeChecksums: true}
	buf := gopacket.NewSerializeBuffer()

	for _, targetHost := range ranges {
		arpPacket.DstProtAddress = []byte(targetHost)
		gopacket.SerializeLayers(buf, opts, ethPacket, arpPacket)
		// if err := ps.WritePacketData(buf.Bytes()); err != nil {
		// 	return err
		// }
		time.Sleep(time.Microsecond * 500)
	}
	return nil
}

func getTargetHostRange(zone *model.Zone, dh *model.DiscoveryHost) ([]net.IP, error) {
	nIP, nIPNet, err := net.ParseCIDR(zone.Network)
	if nil != err {
		return nil, fmt.Errorf("Discovery: Network(%s) of zone is not valid", zone.Network)
	}

	firstIP := net.ParseIP(dh.FirstScanRange)
	lastIP := net.ParseIP(dh.LastScanRange)
	if nil == firstIP || nil == lastIP {
		return nil, fmt.Errorf("Discovery: IP Range(First:%s, Last:%s) is not valid", dh.FirstScanRange, dh.LastScanRange)
	}

	firstIP16 := firstIP.To16()
	lastIP16 := lastIP.To16()
	if nil == firstIP16 || nil == lastIP16 {
		return nil, fmt.Errorf("Discovery: IP Range(First:%s, Last:%s) is not valid", dh.FirstScanRange, dh.LastScanRange)
	}

	excludeIP16s := make([]net.IP, 0)
	for _, eHost := range dh.ExcludeHosts {
		eIP := net.ParseIP(eHost)
		if nil == eIP {
			return nil, fmt.Errorf("Discovery: IP(%v) of exclude host is not valid", eHost)
		}
		eIP16 := eIP.To16()
		if nil == eIP16 {
			return nil, fmt.Errorf("Discovery: IP(%v) of exclude host is not valid", eHost)
		}
		excludeIP16s = append(excludeIP16s, eIP16)
	}

	ranges := make([]net.IP, 0)

	ip := nIP
Loop:
	for ip := ip.Mask(nIPNet.Mask); nIPNet.Contains(ip); inc(ip) {
		ip16 := ip.To16()
		if nil == ip16 {
			return nil, fmt.Errorf("Discovery: IP(%v) converting is failed", ip)
		}

		if 0 > bytes.Compare(ip16, firstIP16) || 0 < bytes.Compare(ip16, lastIP16) {
			continue
		}

		for _, eIP16 := range excludeIP16s {
			if 0 == bytes.Compare(eIP16, ip16) {
				continue Loop
			}
		}

		ranges = append(ranges, ip)
	}

	return ranges, nil
}

func inc(ip net.IP) {
	for j := len(ip) - 1; j >= 0; j-- {
		ip[j]++
		if ip[j] > 0 {
			break
		}
	}
}

func makePacketEthernet(hw net.HardwareAddr) *layers.Ethernet {
	return &layers.Ethernet{
		SrcMAC:       hw,
		DstMAC:       net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
		EthernetType: layers.EthernetTypeARP,
	}
}

func makePacketARP(hw net.HardwareAddr, ip net.IP) *layers.ARP {
	return &layers.ARP{
		AddrType:          layers.LinkTypeEthernet,
		Protocol:          layers.EthernetTypeIPv4,
		HwAddressSize:     6,
		ProtAddressSize:   4,
		Operation:         layers.ARPRequest,
		SourceHwAddress:   []byte(hw),
		SourceProtAddress: []byte(ip),
		DstHwAddress:      []byte{0, 0, 0, 0, 0, 0},
	}
}