package codec

import (
	"bufio"
	"io"
	"net"
	"tpack/proto/packet"
)

type Decoder struct {
	underlying io.Reader
}

func NewDecoder(c net.Conn) *Decoder {
	out := &Decoder{
		underlying: &fullReader{bufio.NewReader(c)},
	}
	return out
}

type fullReader struct{ io.Reader }

func (fr *fullReader) Read(p []byte) (int, error) { return io.ReadFull(fr.Reader, p) }

func (D *Decoder) ReadPacket() (*packet.Packet, error) {
	pkt := &packet.Packet{}
	pkt.Head = &packet.Header{}
	err := pkt.Head.Decode(D.underlying)
	if err != nil {
		return pkt, err
	}
	if pkt.Head.Length < 9 {
		return pkt, err
	}
	pkt.Data = make([]byte, pkt.Head.Length-9)
	err = D.DecryptTo(pkt.Data)
	if err != nil {
		return nil, err
	}
	return pkt, err
}

func (D *Decoder) DecryptTo(b []byte) error {
	_, err := D.underlying.Read(b)
	if err != nil {
		return err
	}
	// you would decrypt the buffer here, since b now holds encrypted data
	return err
}