rui/app_socket.js

var socket
var socketUrl

function sendMessage(message) {
	if (socket) {
		socket.send(message)
	}
}

window.onload = function() {
	socketUrl = document.location.protocol == "https:" ? "wss://" : "ws://" 
	socketUrl += document.location.hostname
	var port = document.location.port
	if (port) {
		socketUrl += ":" + port
	}
	socketUrl += window.location.pathname + "ws"

	socket = new WebSocket(socketUrl);
	socket.onopen = socketOpen;
	socket.onclose = socketClose;
	socket.onerror = socketError;
	socket.onmessage = function(event) {
		window.execScript ? window.execScript(event.data) : window.eval(event.data);
	};
};

function socketOpen() {

	const touch_screen = (('ontouchstart' in document.documentElement) || (navigator.maxTouchPoints > 0) || (navigator.msMaxTouchPoints > 0)) ? "1" : "0";
	var message = "startSession{touch=" + touch_screen 
	
	const style = window.getComputedStyle(document.body);
	if (style) {
		var direction = style.getPropertyValue('direction');
		if (direction) {
			message += ",direction=" + direction
		}
	}

	const lang = window.navigator.language;
	if (lang) {
		message += ",language=\"" + lang + "\"";
	}

	const langs = window.navigator.languages;
	if (langs) {
		message += ",languages=\"" + langs + "\"";
	}

	const userAgent = window.navigator.userAgent
	if (userAgent) {
		message += ",user-agent=\"" + userAgent + "\"";
	}

	const darkThemeMq = window.matchMedia("(prefers-color-scheme: dark)");
	if (darkThemeMq.matches) {
		message += ",dark=1";
	} 

	const pixelRatio = window.devicePixelRatio;
	if (pixelRatio) {
		message += ",pixel-ratio=" + pixelRatio;
	}

	sendMessage( message + "}" );
}

function socketReopen() {
	sendMessage( "reconnect{session=" + sessionID + "}" );
}

function socketReconnect() {
	if (!socket) {
		socket = new WebSocket(socketUrl);
		socket.onopen = socketReopen;
		socket.onclose = socketClose;
		socket.onerror = socketError;
		socket.onmessage = function(event) {
			window.execScript ? window.execScript(event.data) : window.eval(event.data);
		};
	}
}

function socketClose(event) {
	console.log("socket closed")
	socket = null;
	if (!event.wasClean && windowFocus) {
		window.setTimeout(socketReconnect, 10000);
	}
}

function socketError(error) {
	console.log(error);
}

window.onfocus = function(event) {
	windowFocus = true
	if (!socket) {
		socketReconnect()
	} else {
		sendMessage( "session-resume{session=" + sessionID +"}" );
	}
}