package capture

import (
	"fmt"

	"git.freifunk-franken.de/jkimmel/abbel/packet"
	"github.com/google/gopacket"
	"github.com/google/gopacket/afpacket"
	"github.com/google/gopacket/layers"
	"golang.org/x/net/bpf"
	"inet.af/netaddr"
)

var (
	// tcpdump -y RAW -dd ip6 and udp dst port 6696
	babelBPFRAW = []bpf.RawInstruction{
		{0x30, 0, 0, 0x00000000},
		{0x54, 0, 0, 0x000000f0},
		{0x15, 0, 5, 0x00000060},
		{0x30, 0, 0, 0x00000006},
		{0x15, 0, 3, 0x00000011},
		{0x28, 0, 0, 0x0000002a},
		{0x15, 0, 1, 0x00001a28},
		{0x6, 0, 0, 0x00040000},
		{0x6, 0, 0, 0x00000000},
	}
)

type Handle struct {
	tp *afpacket.TPacket
}

func FromInterface(iface string) (Handle, error) {
	var h Handle
	var err error

	if iface != "any" {
		h.tp, err = afpacket.NewTPacket(
			afpacket.SocketDgram,
			afpacket.OptInterface(iface),
		)
	} else {
		h.tp, err = afpacket.NewTPacket(
			afpacket.SocketDgram,
		)
	}

	if err != nil {
		fmt.Println("here")
		return Handle{}, err
	}

	err = h.tp.SetBPF(babelBPFRAW)
	if err != nil {
		return Handle{}, err
	}

	return h, nil
}

func (h Handle) Close() error {
	h.tp.Close()
	return nil
}

func (h Handle) ReadFrom(b []byte) (body []byte, src netaddr.IP, ifindex int, err error) {
	data, ci, err := h.tp.ZeroCopyReadPacketData()
	if err != nil {
		return nil, netaddr.IP{}, 0, err
	}
	pckt := gopacket.NewPacket(data, layers.LayerTypeIPv6, gopacket.NoCopy)
	ip6, ok := pckt.NetworkLayer().(*layers.IPv6)
	if !ok {
		return nil, netaddr.IP{}, 0, fmt.Errorf("Expected IPv6 layer, got %v", pckt.NetworkLayer())
	}

	src, ok = netaddr.FromStdIP(ip6.SrcIP)
	if !ok {
		return nil, netaddr.IP{}, 0, fmt.Errorf("Error parsing packet src address %q", ip6.SrcIP)
	}

	payload := pckt.ApplicationLayer().Payload()
	copy(b, payload)
	b, err = packet.Validate(b[:len(payload)])
	if err != nil {
		return nil, netaddr.IP{}, 0, err
	}

	return b, src, ci.InterfaceIndex, nil
}