diffusion/src/node_modules/transports/subtransports.js

Diffusion JavaScript client

/*eslint valid-jsdoc: "off"*/
var NodeWebSocket = require('ws');

var log = require('util/logger').create('Transports');

/**
 * Support the detection and creation of WebSocket and XmlHttpRequest objects
 * in an environment independent way. Each subtransport object provides an
 * enabled field that indicates if the subtransport works and if it works the
 * environment specific constructor for the object.
 */

/**
 * Optionally environment specific websockets.
 */
function websocketSubTransportFactoryProvider() {
    if (typeof WebSocket === 'function') {
        log.debug('Using native websocket');
        return {
            constructor : WebSocket,
            enabled : true
        };
    } else if (typeof NodeWebSocket === 'function') {
        // Browser version does not include 'ws' lib; use native impl
        log.debug('Using Node WS library');
        return {
            constructor : NodeWebSocket,
            enabled : true
        };
    } else {
        log.debug('Websocket transport not available');
        return {
            enabled : false
        };
    }
}

/**
 * Optionally provide environment specific XHR.
 */
function xhrSubTransportFactoryProvider() {
    if (typeof XMLHttpRequest === 'function') {
        log.debug('Using native XHR');
        return {
            constructor : XMLHttpRequest,
            enabled : true
        };
    } else {
        log.debug('XHR transport not available');
        return {
            enabled : false
        };
    }
}

/**
 * The subtransports will be looked up by transport name.
 */
module.exports = {
    /**
     * WebSocket subtransport. Supports detection of availability and construction when available.
     */
    WS : websocketSubTransportFactoryProvider(),
    /**
     * HTTP polling subtransport. Supports detection of availability and construction when available.
     */
    XHR : xhrSubTransportFactoryProvider(),
    /**
     * WebSocket subtransport. Supports detection of availability and construction when available.
     */
    WEBSOCKET : websocketSubTransportFactoryProvider(),
    /**
     * HTTP polling subtransport. Supports detection of availability and construction when available.
     */
    HTTP_POLLING : xhrSubTransportFactoryProvider()
};