package shadow

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"net"
)

var (
	AppDataHeader = []byte("GGGGGGGG")
	HeaderLength  = len(AppDataHeader)
)

type PackAppData struct {
	Conn net.Conn
}

func (m PackAppData) Read(p []byte) (n int, err error) {
	buf := make([]byte, 32*1024)
	read, err := m.Conn.Read(buf[0 : HeaderLength+2])
	if bytes.Equal(buf[0:HeaderLength], AppDataHeader) {
		u := int(binary.BigEndian.Uint16(buf[HeaderLength : HeaderLength+2]))
		r, err := m.Conn.Read(buf[HeaderLength+2 : u+HeaderLength+2])
		copy(p, buf[HeaderLength+2:r+HeaderLength+2])
		return r, err
	} else {
		fmt.Println("Header is not present")
		return read, err
	}
}

func (m PackAppData) Write(p []byte) (n int, err error) {
	t := make([]byte, len(p)+HeaderLength+2)
	copy(t[0:], AppDataHeader)
	binary.BigEndian.PutUint16(t[HeaderLength:], uint16(len(p)))
	copy(t[HeaderLength+2:], p)
	write, err := m.Conn.Write(t)
	write = write - HeaderLength - 2
	return write, err
}

func (m PackAppData) Close() error {
	return m.Conn.Close()
}