rxprotoplex-websocket/lib/WebSocketStream.js

A lightweight library for creating Plex connections over WebSocket, enabling multiplexed communication for real-time applications.

import { Duplex } from "streamx";
import b4a from "b4a";

class WebSocketStream extends Duplex {
    constructor (isInitiator, socket) {
        super({
            mapWritable: (data) => typeof data === "string" ? b4a.from(data) : data
        });

        this._socket = socket;
        this._socket.binaryType = 'arraybuffer';

        this._opening = null;

        this._onError = onError.bind(this);
        this._onClose = onClose.bind(this);
        this._onOpen = onOpen.bind(this);
        this._onMessage = onMessage.bind(this);

        this._socket.addEventListener('error', this._onError);
        this._socket.addEventListener('close', this._onClose);
        this._socket.addEventListener('open', this._onOpen);
        this._socket.addEventListener('message', this._onMessage);
    }

    _open (cb) {
        if (this._socket.readyState > 1) cb(new Error('Socket is closed'));
        else if (this._socket.readyState < 1) this._opening = cb;
        else cb(null);
    }

    _continueOpen (err) {
        if (err) this.destroy(err);

        const cb = this._opening;

        if (cb) {
            this._opening = null;
            this._open(cb);
        }
    }

    _write (data, cb) {
        this._socket.send(data);
        cb(null);
    }

    _predestroy () {
        this._continueOpen(new Error('Socket was destroyed'));
    }

    _destroy (cb) {
        if (this._socket) {
            this._socket.removeEventListener('error', this._onError);
            this._socket.removeEventListener('close', this._onClose);
            this._socket.removeEventListener('open', this._onOpen);
            this._socket.removeEventListener('message', this._onMessage);

            if (this._socket.readyState < 2) {
                this._socket.close();  // Close only if still open
            }
        }
        cb(null);
    }
}

function onError (err) {
    console.error("WebSocketStream error:", err);
    this.destroy(err);
}

function onClose () {
    this._socket.removeEventListener('error', this._onError);
    this._socket.removeEventListener('close', this._onClose);
    this._socket.removeEventListener('open', this._onOpen);
    this._socket.removeEventListener('message', this._onMessage);

    this.destroy();
}

function onOpen () {
    this._continueOpen();
}

function onMessage (event) {
    this.push(b4a.from(event.data));
}

export { WebSocketStream };