package shadow

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

var (
	AppDataHeader = []byte{0x17, 0x3, 0x3}
	HeaderLength  = len(AppDataHeader)
)

type PackAppData struct {
	Conn net.Conn
}

func (m PackAppData) Read(p []byte) (n int, err error) {

	buf := make([]byte, 32*1024+HeaderLength+2)

	headRead, err := io.ReadAtLeast(m.Conn, buf[0:HeaderLength+2], HeaderLength+2)
	if err != nil {
		if err != io.EOF {
			fmt.Printf("Read header error: %v\n", err)
		}
		return 0, err
	}
	if headRead < HeaderLength+2 {
		return 0, errors.New("Read header failed")
	}
	if bytes.Equal(buf[0:HeaderLength], AppDataHeader) {
		payLoadLength := int(binary.BigEndian.Uint16(buf[HeaderLength : HeaderLength+2]))
		sum := 0
		for sum < payLoadLength {
			r, e := m.Conn.Read(buf[HeaderLength+2+sum : HeaderLength+2+payLoadLength])
			if e != nil {
				if e == io.EOF {
					break
				} else {
					return 0, e
				}
			}
			copy(p[sum:], buf[HeaderLength+2+sum:HeaderLength+2+sum+r])
			sum += r
		}
		return sum, err
	} else {
		fmt.Printf("Invalid header")
		return 0, errors.New("invalid header")
	}
}

func (m PackAppData) Write(p []byte) (n int, err error) {
	lenNum := make([]byte, 2)
	binary.BigEndian.PutUint16(lenNum, uint16(len(p)))

	packetBuf := bytes.NewBuffer(AppDataHeader)
	packetBuf.Write(lenNum)
	packetBuf.Write(p)

	write, err := m.Conn.Write(packetBuf.Bytes())
	write = write - HeaderLength - 2
	return write, err
}

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