package crypto

import (
	"crypto/rc4"
	"encoding/binary"
)

type Ciphers struct {
	client *rc4.Cipher // For decryption (client->server)
	server *rc4.Cipher // For encryption (server->client)
}

// NewCiphers creates a new pair of RC4 ciphers for the client and server
func NewCiphers(key int64) (*Ciphers, error) {
	keyBytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(keyBytes, uint64(key))

	// Client cipher uses NOT of key
	clientKeyBytes := make([]byte, 8)
	binary.LittleEndian.PutUint64(clientKeyBytes, uint64(^key))

	clientCipher, err := rc4.NewCipher(keyBytes)
	if err != nil {
		return nil, err
	}

	serverCipher, err := rc4.NewCipher(clientKeyBytes)
	if err != nil {
		return nil, err
	}

	// Drop first 20 bytes from both ciphers
	drop := make([]byte, 20)
	clientCipher.XORKeyStream(drop, drop)
	serverCipher.XORKeyStream(drop, drop)

	return &Ciphers{
		client: clientCipher,
		server: serverCipher,
	}, nil
}

// Decrypt decrypts data received from the client
func (c *Ciphers) Decrypt(data []byte) {
	if c.client != nil {
		c.client.XORKeyStream(data, data)
	}
}

// Encrypt encrypts data to be sent to the client
func (c *Ciphers) Encrypt(data []byte) {
	if c.server != nil {
		c.server.XORKeyStream(data, data)
	}
}