desk2/client/websocket.js

// Firefox does randomized exponential backoff for failed websocket requests
// This means we can't have [1. long downtime] and [2. fast reconnect] at the sime time
//
// We abuse the fact that HTTP requests are NOT backoffed, and use those to monitor 
// the server. When we see that the server is up - we attempt an actual websocket connection
//
// Details best described here: https://github.com/kee-org/KeeFox/issues/189

function ws_connect(first_connect = false) {
    const session_id = ls.getItem('sessionId') || '0';
    const desk_id = storage.desk_id;

    ws = new WebSocket(`${config.ws_url}?deskId=${desk_id}&sessionId=${session_id}`);
    
    ws.addEventListener('open', on_open);
    ws.addEventListener('message', on_message);
    ws.addEventListener('error', on_error);
    ws.addEventListener('close', on_close);
}

function on_open() {
    clearTimeout(storage.timers.ws_reconnect);
    if (config.debug_print) console.debug('open')
}

async function on_message(event) {
    const data = event.data;
    let message_data = null;

    if ('arrayBuffer' in data) {
        message_data = await data.arrayBuffer();
        const view = new DataView(message_data);
        const d = deserializer_create(message_data, view);
        await handle_message(d);
    } else {
        /* For all my Safari < 14 bros out there */
        const reader = new FileReader();
        reader.onload = async (e) => {
            message_data = e.target.result;
            const view = new DataView(message_data);
            const d = deserializer_create(message_data, view);
            await handle_message(d);
        };

        reader.readAsArrayBuffer(data);
    }
}

function on_close() {
    ws = null;
    if (config.debug_print) console.debug('close');
    storage.timers.ws_reconnect = setTimeout(ws_connect, config.ws_reconnect_timeout);
}

function on_error() {
    ws.close();
}