package tun

import (
	wgtun "golang.zx2c4.com/wireguard/tun"
	"io"
	"log"
	"mpbl3p/proxy"
	"os"
)

type SourceSink struct {
	tun wgtun.Device
}

func NewTun(name string, mtu int) (t wgtun.Device, err error) {
	return wgtun.CreateTUN(name, mtu)
}

func NewFromFile(fd uintptr, mtu int) (ss *SourceSink, err error) {
	ss = new(SourceSink)

	file := os.NewFile(fd, "")
	ss.tun, err = wgtun.CreateTUNFromFile(file, mtu)
	if err != nil {
		return
	}

	return
}

func (t *SourceSink) Close() error {
	return t.tun.Close()
}

func (t *SourceSink) Source() (proxy.Packet, error) {
	mtu, err := t.tun.MTU()
	if err != nil {
		return nil, err
	}

	buf := make([]byte, mtu+4)

	read, err := t.tun.Read(buf, 4)
	if err != nil {
		return nil, err
	}

	if read == 0 {
		return nil, io.EOF
	}

	return proxy.SimplePacket(buf[4 : read+4]), nil
}

var good, bad float64

func (t *SourceSink) Sink(packet proxy.Packet) error {
	// make space for tun header
	content := make([]byte, len(packet.Contents())+4)
	copy(content[4:], packet.Contents())

	_, err := t.tun.Write(content, 4)
	if err != nil {
		switch err.(type) {
		case *os.PathError:
			bad += 1
			log.Printf("packet loss: %f%%\n", bad*100/(good+bad))
			return nil
		default:
			return err
		}
	}

	good += 1
	return nil
}