package utils

import (
	"log"
	"github.com/google/gopacket"

	"saprusserver/structs"
)

func (c* SocketCall) FileTransferPacket(message string) gopacket.SerializeBuffer {
        eth, ip, udp := basePacket(c)

        sapFile := structs.SaprusFileTransfer {
                Flag:           [1]byte{0x11},
                Sequence:       [2]byte{0x22, 0x33},
                Checksum:       [2]byte{0x44, 0x44},
                Payload:        []byte(message),
        }

        sapHeader := structs.SaprusHeaderFrame {
                PacketType:     [2]byte{0x88, 0x88},
                Length:         c.saprusPayloadLength(sapFile.Bytes()),
                Payload:        sapFile.Bytes(),
        }

        buf := gopacket.NewSerializeBuffer()
        opts := gopacket.SerializeOptions {
                ComputeChecksums:       true,
                FixLengths:             true,
        }

        udp.SetNetworkLayerForChecksum(&ip)
        err := gopacket.SerializeLayers(buf, opts, &eth, &ip, &udp, gopacket.Payload(sapHeader.Bytes()))
        if err != nil {
                log.Panic(err)
        }
        return buf
}