package monitor

import (
	"context"
	"encoding/hex"
	"github.com/google/gopacket"
	"github.com/google/gopacket/pcap"
	"github.com/pkg/errors"
	"log/slog"
)

func Start(ctx context.Context, errCh chan error) {

	// 打开一个网络接口
	device, err := pcap.OpenLive("WLAN", 1600, true, pcap.BlockForever)
	if err != nil {
		b, er := hex.DecodeString("\\xbb")
		slog.Debug("b", b, er)
		errCh <- errors.Wrap(err, "打开网络接口失败")
		return
	}
	defer device.Close()

	err = device.SetBPFFilter("tcp")
	if err != nil {
		errCh <- errors.Wrap(err, "设置 BPF 过滤器失败")
		return
	}

	err = device.SetDirection(pcap.DirectionIn)
	if err != nil {
		errCh <- errors.Wrap(err, "设置捕获方向失败")
		return
	}

	// 创建一个数据包源
	source := gopacket.NewPacketSource(device, device.LinkType())
	source.NoCopy = true
	source.Lazy = true

	for {
		select {
		case <-ctx.Done():
			slog.Debug("monitor 被动结束")
			errCh <- nil
			return

		case packet := <-source.Packets():
			handle(packet)
		}
	}
}

func handle(packet gopacket.Packet) {
	slog.Debug("Packet: ", packet)
	slog.Debug("Layers: ", packet.Layers())
	slog.Debug("Application: ", packet.ApplicationLayer())
	slog.Debug("Transport: ", packet.TransportLayer())
	slog.Debug("Network: ", packet.NetworkLayer())
	slog.Debug("Link: ", packet.LinkLayer())
}