// 13 b4 37 XX XX XX XX > (pk) - Authenticated
// 13 37 > (pk) - I am <...>
// e7 5a 3d ed > (gk) - Authenticate yourself
// 55 44 e9 37 < (pk) - Forget me
// e7 5a 3d ea > (pk) - Forget me. OK

const dgram = require('dgram');
const net = require('net');
const { Tun } = require('tuntap2');
const { encrypt, decrypt } = require('../encryption');
const IP = require('ip-packet');
const sock = dgram.createSocket('udp4');

const tun = new Tun();

var established = false;

sock.on('message', (msg, info) => {
    const pd = decrypt(msg, config.privateKey, config.iv, config.algorithm);
    const gd = decrypt(msg, config.globalKey, config.iv, config.algorithm);
    const dec = pd.length == 0 ? gd : pd;
    if (dec.length == 4 && dec[0] == 0xe7 && dec[1] == 0x5a && dec[2] == 0x3d && dec[3] == 0xed) {
        console.log(`Server asks to authenticate. Authenticating...`);
        authenticateAndCheck();
        return;
    }
    if (dec.length == 7 && dec[0] == 0x13 && dec[1] == 0xb4 && dec[2] == 0x37) {
        const ip = dec.slice(3);
        const strIp = ip.map(s => s.toString()).join('.');
        console.log(`My IP: ${strIp}`);
        tun.mtu = config.mtu;
        tun.ipv4 = `${strIp}/${config.len}`;
        tun.isUp = true;
        tun.on('data', (d) => {
            sock.send(
                encrypt(
                    d,
                    config.privateKey,
                    config.iv,
                    config.algorithm
                ),
                config.port,
                config.endpoint
            );
        });
        established = true;
    }
    if (established && (dec[0] >> 4 == 4)) {
        tun.write(dec);
    }
});

function authenticate() {
    sock.send(
        encrypt(
            Buffer.from([
                0x13, 0x37
            ]),
            config.privateKey,
            config.iv,
            config.algorithm
        ),
        config.port,
        config.endpoint
    );
}

function authenticateAndCheck() {
    authenticate();

    var i = setInterval(() => {
        if (!established) {
            console.log(`Connection not established. Authenticating again...`);
            authenticate();
        } else {
            clearInterval(i);
            console.log(`Authenticated.`);
        }
    }, 2000);
}

authenticateAndCheck();