// rework to use chunkermaster

const fs = require("fs");
const path = require("path");
const { createConnection } = require('net');
const { createHash, createECDH, createCipheriv, createDecipheriv, randomBytes } = require('crypto');
const { Transform } = require('stream');

// Application settings
const port = process.argv[3] || 23;
const hostname = process.argv[2] || (process.pkg ? "dom.ht-dev.de" : "localhost");
let delayMs = process.argv[4] || 100; // Command delay in milliseconds
const encryptionDelay = 200; // additional delay for encryption
const initializationDelay = 500; // additional delay for initialization

const advancedFeatures = true; // Enable advanced features
const printIO = false; // Print input/output data

class MemoryStream extends Transform {
    constructor(options = {}) {
        super(options);
    }

    _transform(chunk, encoding, callback) {
        this.push(chunk);
        callback();
    }
}

/**
 * prepare the session and close handler when done
 * @param {Buffer} data
 * @returns {Buffer[]} chunks
 */
function chunkData(data) {
    // Split data into chunks based on IAC
    const chunks = [];
    let currentChunk = Buffer.alloc(0);

    for (let i = 0; i < data.length; i++) {
        if (data[i] === IAC[0]) {
            if (currentChunk.length > 0) {
                chunks.push(currentChunk);
            }
            // Find the end of the IAC command
            let cmdLength = 3; // Default IAC command length
            if (data[i + 1] === SB[0]) {
                // Find SE to end subnegotiation
                const seIndex = data.indexOf(SE[0], i);
                cmdLength = seIndex - i + 1;
            }
            chunks.push(data.subarray(i, i + cmdLength));
            i += cmdLength - 1;
            currentChunk = Buffer.alloc(0);
        } else {
            currentChunk = Buffer.concat([currentChunk, Buffer.from([data[i]])]);
        }
    }

    if (currentChunk.length > 0) {
        chunks.push(currentChunk);
    }

    return chunks;
}

const writer = new MemoryStream();
let initialized = false; // Initialization status, do not modify directly, runtime only
let handoffInit = false; // Handoff initialization status to server, do not modify directly, runtime only
let encrypted = false; // Encryption status, do not modify directly, runtime only
let privateKey; // Private key, do not modify directly, runtime only
let keyCurve; // Key curve, do not modify directly, runtime only
let encryptionAlgorithm; // Encryption algorithm, do not modify directly, runtime only
let echdKey; // ECDH key, do not modify directly, runtime only

const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms));

const send = async (command) => {
    await delay(delayMs);
    writer.write(command); // Command
    await delay(delayMs);
    writer.write("\r\n"); // Line Feed
};

// Numeric Buffer values
const NUL = Buffer.from([0x00]); // Null
const ONE = Buffer.from([0x01]); // One

// Telnet commands
const IAC = Buffer.from([0xff]); // Interpret As Command
const DONT = Buffer.from([0xfe]); // Don't
const DO = Buffer.from([0xfd]); // Do
const WONT = Buffer.from([0xfc]); // Won't
const WILL = Buffer.from([0xfb]); // Will
const SB = Buffer.from([0xfa]); // Subnegotiation Begin
const GA = Buffer.from([0xf9]); // Go Ahead
const EL = Buffer.from([0xf8]); // Erase Line
const EC = Buffer.from([0xf7]); // Erase Character
const AYT = Buffer.from([0xf6]); // Are You There
const AO = Buffer.from([0xf5]); // Abort Output
const IP = Buffer.from([0xf4]); // Interrupt Process
const BRK = Buffer.from([0xf3]); // Break
const DM = Buffer.from([0xf2]); // Data Mark
const NOP = Buffer.from([0xf1]); // No Operation
const SE = Buffer.from([0xf0]); // Subnegotiation End

// Common Telnet options or features
const ECHO = Buffer.from([0x01]); // Echo
const SUPPRESS_GO_AHEAD = Buffer.from([0x03]); // Suppress Go Ahead
const STATUS = Buffer.from([0x05]); // Status
const TIMING_MARK = Buffer.from([0x06]); // Timing Mark
const TERMINAL_TYPE = Buffer.from([0x18]); // Terminal Type
const NAWS = Buffer.from([0x1f]); // Negotiate About Window Size
const TERMINAL_SPEED = Buffer.from([0x20]); // Terminal Speed
const REMOTE_FLOW_CONTROL = Buffer.from([0x21]); // Remote Flow Control
const LINEMODE = Buffer.from([0x22]); // Line Mode
const ENVIRONMENT_VARIABLES = Buffer.from([0x24]); // Environment Variables

// custom codes for own client
const CUSTOM_CLIENT_INIT = Buffer.from([0x80]); // Custom Client Initialization
const KEY_EXCHANGE = Buffer.from([0x81]); // Key Exchange
const ENCRYPTION = Buffer.from([0x82]); // Encryption
const AUTHENTICATION = Buffer.from([0x83]); // Authentication
// 0x84 reserved for future use
const FILE_TRANSFER = Buffer.from([0x85]); // File Transfer
const PAUSE = Buffer.from([0x86]); // Pause
const RESUME = Buffer.from([0x87]); // Resume
const START_CONTENT = Buffer.from([0x88]); // Start Content
const END_CONTENT = Buffer.from([0x89]); // End Content

// ANSI escape codes for colors
const ANSI = {
    // Reset
    reset: '\x1b[0m',

    // Basic foreground colors
    black: '\x1b[30m',
    red: '\x1b[31m',
    green: '\x1b[32m',
    yellow: '\x1b[33m',
    blue: '\x1b[34m',
    magenta: '\x1b[35m',
    cyan: '\x1b[36m',
    white: '\x1b[37m',

    // Bright foreground colors
    brightBlack: '\x1b[90m',
    brightRed: '\x1b[91m',
    brightGreen: '\x1b[92m',
    brightYellow: '\x1b[93m',
    brightBlue: '\x1b[94m',
    brightMagenta: '\x1b[95m',
    brightCyan: '\x1b[96m',
    brightWhite: '\x1b[97m',

    // Basic background colors
    bgBlack: '\x1b[40m',
    bgRed: '\x1b[41m',
    bgGreen: '\x1b[42m',
    bgYellow: '\x1b[43m',
    bgBlue: '\x1b[44m',
    bgMagenta: '\x1b[45m',
    bgCyan: '\x1b[46m',
    bgWhite: '\x1b[47m'
};

// Encrypt
function encrypt(plaintext, key = privateKey, encoding = 'utf8') {
    // Generate a random IV (12 bytes recommended for GCM)
    const iv = randomBytes(12);

    // Create cipher, providing algo, key, and IV
    const cipher = createCipheriv(encryptionAlgorithm, key, iv);

    // Encrypt data
    const encrypted = Buffer.concat([cipher.update(plaintext, encoding), cipher.final()]);
    const authTag = cipher.getAuthTag(); // Integrity tag

    // Return IV + tag + ciphertext
    return Buffer.concat([iv, authTag, encrypted]);
}

// Decrypt
function decrypt(ciphertext, key = privateKey, encoding = 'utf8') {
    // Extract IV (first 12 bytes)
    const iv = ciphertext.slice(0, 12);
    
    // Extract tag (next 16 bytes)
    const tag = ciphertext.slice(12, 28);
    
    // Remainder is the actual encrypted data
    const data = ciphertext.slice(28);

    // Create decipher, set auth tag
    const decipher = createDecipheriv(encryptionAlgorithm, key, iv);
    decipher.setAuthTag(tag);

    // Decrypt data
    const decrypted = Buffer.concat([decipher.update(data), decipher.final()]);
    return decrypted.toString(encoding);
}

//  Set the path of the project folder base on whether it is run with nodejs or as an executable
let project_folder;
if (process.pkg) {
    //  It is run as an executable
    project_folder = path.dirname(process.execPath)

} else {
    //  It is run with nodejs
    project_folder = __dirname
}

if (process.pkg) {
    console.debug = () => { }; // Disable debug logging when run as an executable
    fs.writeFileSync(path.join(project_folder, "README.md"), fs.readFileSync(path.join(__dirname, "README.md"))); // copy newest readme to folder
    fs.writeFileSync(path.join(project_folder, "LICENSE"), fs.readFileSync(path.join(__dirname, "LICENSE"))); // copy newest license to folder
}

const socket = createConnection(port, hostname);

writer.pipe(socket);

let hold = false; // Hold input
let holdBuffer = ""; // Buffer data when on hold

process.stdin.setEncoding("ascii");
process.stdin.setRawMode(true);
process.stdin.resume();

// format keys before sending to server
process.stdin.on('data', async (key) => {
    if (key === '\u0004') { // Ctrl+D
        socket.end(); // End connection
        socket.destroy(); // Destroy socket
        process.exit(); // Exit process
    } else if (key === '\u0003') { // Ctrl+C
        send(IP); // Interrupt Process
    } else if (key === '\u0018') { // Ctrl+X
        process.stdout.write("\r");
        console.log("Entered client command mode");
        hold = true; // Hold input
        process.stdin.setRawMode(false);
        // Add any additional functionality for Ctrl+X here
    }

    // Log Unicode values of input for debugging
    // console.debug("Key pressed:", Array.from(key).map(b => '\\u' + b.toString(16).padStart(4, '0')));

    if (key == "\r") {
        // Enter key
        socket.write("\r\n");
    } else if (!hold) {
        socket.write(key);
    } else {
        // console.debug("Input on hold");
        const command = key.replace(/\r?\n|\r/g, ''); // Remove new line characters
        if (["exit", "quit"].includes(command)) {
            hold = false; // Release input
            process.stdin.setRawMode(true);
            console.log("Exited client command mode");
            process.stdout.write(holdBuffer);
            holdBuffer = "";
            process.stdout.write("> ");
        } else if (command == "disconnect") {
            send(IP); // Interrupt Process
            socket.end(); // End connection
        } else if (command == "status") {
            console.log("Client status:");
            console.log("Host:", hostname + ":" + port);
            console.log("Advanced Features unlocked:", advancedFeatures);
            console.log("Initialized:", initialized);
            console.log("Encrypted:", encrypted);
            console.log("Batch Delay:", delayMs + "ms");
            // console.log("Public Key:", key.getPublicKey() ? key.getPublicKey().toString("hex") : "null");
            // console.log("Private Key:", privateKey ? privateKey.toString("hex") : "null");
            process.stdout.write("$ ");
        } else if (command == "debug") {
            socket.write(Buffer.concat([IAC, DO, STATUS])); // Debug request Status
            setTimeout(() => {
                process.stdout.write("$ ");
            }, delayMs);
        } else if (command == "keyinfo") {
            console.log("Key Information:");
            console.log("Key Curve:", keyCurve);
            console.log("Encryption Algorithm:", encryptionAlgorithm);
            console.log("Public Key:", echdKey.getPublicKey() ? echdKey.getPublicKey().toString("hex") : "null");
            console.log("Private Key:", privateKey ? privateKey.toString("hex") : "null");
            process.stdout.write("$ ");
        } else if (command == "help") {
            // Add any additional functionality for client side commands
            console.log("Client commands:");
            console.log("status - Show client status");
            console.log("debug - [DEV] Request server status");
            console.log("keyinfo - Show key information");
            console.log("disconnect - Disconnect from server");
            console.log("exit - Exit client command mode");
            process.stdout.write("$ ");
        } else {
            process.stdout.write("$ ");
        }
    }
});

socket.on("data", (data) => {
    const chunks = chunkData(data);
    for (const chunk of chunks) {
        if (printIO) {
            console.debug("Received chunk:", chunk.toString("hex"));
        }
        if (!encrypted || !initialized) {
            if (chunk.equals(PAUSE)) {
                process.stdin.pause();
            } else if (chunk.equals(RESUME)) {
                process.stdin.resume();
            } else if (chunk.equals(IP)) {
                process.exit();
            } else if (chunk.includes(Buffer.concat([IAC, SB, CUSTOM_CLIENT_INIT, NUL]))) {
                const offsetBegin = chunk.indexOf(SB) + 2;
                const offsetEnd = chunk.lastIndexOf(SE) - 1;
                const algorithmData = chunk.subarray(offsetBegin + 1, offsetEnd);
                keyCurve = algorithmData.toString('utf8');
                echdKey = createECDH(keyCurve);
                console.debug("Using key curve:", keyCurve);
            } else if (chunk.equals(Buffer.concat([IAC, DO, CUSTOM_CLIENT_INIT]))) {
                // server supports custom client features
                socket.write(Buffer.concat([IAC, WILL, KEY_EXCHANGE])); // Start Key Exchange
            } else if (chunk.includes(Buffer.concat([IAC, DO, KEY_EXCHANGE]))) {
                // generate keys
                const publicKey = echdKey.generateKeys();
                console.debug("Generated Key: " + publicKey.toString("hex"));
            } else if (chunk.equals(Buffer.concat([IAC, SB, KEY_EXCHANGE, ONE /* value required */, IAC, SE]))) {
                socket.write(Buffer.concat([IAC, SB, KEY_EXCHANGE, NUL, echdKey.getPublicKey(), IAC, SE]));
                // send key to server
            } else if (chunk.includes(Buffer.concat([IAC, SB, KEY_EXCHANGE, NUL /* value provided */]))) {
                // server sent its key, generate secret
                console.debug("Key exchange received");
                const offsetBegin = chunk.indexOf(SB) + 2;
                const offsetEnd = chunk.lastIndexOf(SE) - 1;
                const keyData = chunk.subarray(offsetBegin + 1, offsetEnd); // client public key
                console.log("Extracted key:", keyData.toString("hex"));
                privateKey = echdKey.computeSecret(keyData);
                socket.write(Buffer.concat([IAC, WILL, ENCRYPTION])); // Enable Encryption
            } else if (chunk.includes(Buffer.concat([IAC, SB, STATUS, NUL /* value provided */]))) {
                // server sent status
                const offsetBegin = chunk.indexOf(SB) + 2;
                const offsetEnd = chunk.lastIndexOf(SE) - 1;
                const statusData = chunk.subarray(offsetBegin + 1, offsetEnd);
                console.debug("Server status:", require("util").inspect(JSON.parse(statusData.toString('utf8'))));
            } else if (chunk.includes(Buffer.concat([IAC, SB, ENCRYPTION, NUL]))) {
                const offsetBegin = chunk.indexOf(SB) + 2;
                const offsetEnd = chunk.lastIndexOf(SE) - 1;
                const algorithmData = chunk.subarray(offsetBegin + 1, offsetEnd);
                encryptionAlgorithm = algorithmData.toString('utf8');
                console.debug("Using encryption algorithm:", encryptionAlgorithm);
            } else if (chunk.equals(Buffer.concat([IAC, DO, ENCRYPTION]))) {
                // enable encryption
                encrypted = true;
                console.debug("Encryption enabled");
                console.debug("Private Key: " + privateKey.toString("hex"));
            } else if (chunk.equals(Buffer.concat([IAC, DO, Buffer.from([0x80])]))) {
                handoffInit = true;
                console.debug("Handoff initialization complete");
            } else if (chunk.equals(Buffer.concat([IAC, DO, Buffer.from([0x80])]))) { // Initialize
                socket.write(Buffer.concat([IAC, WILL, Buffer.from([0x80])]));
                initialized = true;
                console.debug("Initialization complete");
            } else if (!hold) {
                process.stdout.write(chunk);
            } else {
                // console.debug("Data on hold");
                holdBuffer += chunk.toString();
            }
        } else {
            // decrypt data
            try {
                const decryptedData = decrypt(chunk, privateKey);
                process.stdout.write(decryptedData);
            } catch (error) {
                console.error("Decryption error:", error);
                console.error("Data:", chunk.toString("hex"));
                console.debug("Algorithm:", encryptionAlgorithm);
                console.debug("Private Key:", privateKey.toString("hex"));
                console.debug("Public Key:", echdKey.getPublicKey().toString("hex"));
            }
        }
    }
});

socket.on("connect", async () => {
    console.log("Connected to server");
    process.stdin.pause(); // Pause input

    // initialization
    const columns = process.stdout.columns || 80;
    const rows = process.stdout.rows || 24;

    // Create buffer for window size: [columns-high, columns-low, rows-high, rows-low]
    const windowSize = Buffer.from([
        (columns >> 8) & 0xFF,  // high byte of columns
        columns & 0xFF,         // low byte of columns
        (rows >> 8) & 0xFF,    // high byte of rows
        rows & 0xFF            // low byte of rows
    ]);
    socket.write(Buffer.concat([IAC, WILL, NAWS, SB, NAWS, windowSize, SE])); // Negotiate About Window Size
    await delay(delayMs); // Wait for server to process
    socket.write(Buffer.concat([IAC, WILL, TERMINAL_TYPE, IAC, SB, TERMINAL_TYPE, NUL, Buffer.from("xterm-256color"), IAC, SE])); // Terminal Type
    await delay(delayMs);
    socket.write(Buffer.concat([IAC, DO, ECHO])); // Tell server to echo input
    await delay(delayMs);
    if (advancedFeatures) {
        socket.write(Buffer.concat([IAC, WILL, CUSTOM_CLIENT_INIT])); // Custom Client Initialization
        await delay(delayMs);
    }
    if (encrypted) {
        // increase delay for encryption
        delayMs += encryptionDelay;
    }
    await delay(initializationDelay); // Wait for server to process
    await send(""); // Send empty command to initialize connection

    if (!handoffInit) {
        initialized = true; // Initialization is now handled by server
        console.debug("Initialization complete");
    }

    // socket.write(Buffer.from([0x0d, 0x0a])); // Line Feed
    // from here on encryption is enabled, do not use socket.write() directly anymore
    // initialization complete

    await send("help");
    await delay(delayMs);
    process.stdout.write("\r" + ANSI.bgRed + ANSI.white + "DEPRECATION NOTICE:" + ANSI.reset + " This is an unsupported version and might not work fully." + "\r\n");
    process.stdout.write("\rCtrl+X for client side commands\r\nCtrl+C to exit, Ctrl+D to force close\r\n> ");
    process.stdin.resume(); // Resume input
    // more commands can be added here

    // console.log("Test:", decrypt(Buffer.from("eaffd8d028120ac5b1e8634438c522a91ca5bd9cbda1c5ac88321cd6d743b185b6e43cec1c1d6b1b1ad5fc623012582e666a0d1b83f7656dbdd2a8609e0ec9f1e6123ebb442455316a4bfe883d46", "hex"), privateKey))

    if (fs.existsSync("batchrun.txt")) {
        const batchCommands = fs.readFileSync("batchrun.txt", "utf-8").split("\n");
        for (const command of batchCommands) {
            if (command.trim()) {
                await send(command.trim());
                await delay(delayMs);
            }
        }
    }

});

socket.on("end", () => {
    console.log("\nDisconnected from server");
    process.exit();
});

process.on('uncaughtException', (err) => {
    if (err.code === 'ECONNRESET') {
        console.warn("\nDisconnected from server");
        process.exit();
        } else if (err.code === 'ECONNREFUSED') {
        console.warn("Connection refused");
        process.exit();
        } else if (err.code === 'ETIMEDOUT') {
        console.warn("Connection timed out");
        process.exit();
        } else if (err.code === 'EHOSTUNREACH') {
        console.warn("Host is unreachable");
        process.exit();
        } else if (err.code === 'ENETUNREACH') {
        console.warn("Network is unreachable"); 
        process.exit();
    } else {
        console.error('Unhandled exception:', err);
        process.exit(1);
    }
});

module.exports = {
    delay,
    send,
    project_folder
};