package obfuscated2

import (
	"io"

	"github.com/go-faster/errors"

	"github.com/gotd/td/internal/mtproxy"
)

// Obfuscated2 implements obfuscated2 obfuscation protocol.
type Obfuscated2 struct {
	rand io.Reader
	conn io.ReadWriter

	keys
}

// NewObfuscated2 creates new Obfuscated2.
func NewObfuscated2(r io.Reader, conn io.ReadWriter) *Obfuscated2 {
	return &Obfuscated2{
		rand: r,
		conn: conn,
	}
}

// Handshake sends obfuscated2 header.
func (o *Obfuscated2) Handshake(protocol [4]byte, dc int, s mtproxy.Secret) error {
	k, err := generateKeys(o.rand, protocol, s.Secret, dc)
	if err != nil {
		return errors.Wrap(err, "generate keys")
	}
	o.keys = k

	if _, err := o.conn.Write(o.header); err != nil {
		return errors.Wrap(err, "write obfuscated header")
	}

	return nil
}

// Write implements io.Writer.
func (o *Obfuscated2) Write(b []byte) (n int, err error) {
	cpyB := append([]byte(nil), b...)
	o.encrypt.XORKeyStream(cpyB, b)
	return o.conn.Write(cpyB)
}

// Read implements io.Reader.
func (o *Obfuscated2) Read(b []byte) (int, error) {
	n, err := o.conn.Read(b)
	if err != nil {
		return n, err
	}
	if n > 0 {
		o.decrypt.XORKeyStream(b, b)
	}
	return n, err
}