Node.js proxy helper module

proxy-helper.js

/**
 * Outbound proxy helper library.
 * @module lib/proxy-helper
 */

// Reference: http://stackoverflow.com/a/29738070/400347

"use strict";

let defaultOverrideHosts = ['localhost', '127.0.0.1'];

let url    = require('url');
let tunnel = require('tunnel');
let logger = require('./logger');

let tunnels = [];

exports.setOutboundHttpProxy = function (proxyUrl, overrideHosts) {
    let http = require('http');
    setOutboundProxy(http, false, proxyUrl, overrideHosts);
};

exports.setOutboundHttpsProxy = function (proxyUrl, overrideHosts) {
    let https = require('https');
    setOutboundProxy(https, true, proxyUrl, overrideHosts);
};

function setOutboundProxy(library, isForHttpsRequests, proxyUrl, overrideHosts) {
    if (!proxyUrl) { return; }

    let skipHosts = (overrideHosts || defaultOverrideHosts).map(function (v) { return v.toLowerCase(); });

    let tunnelingAgent = getTunnelingAgent(isForHttpsRequests, proxyUrl);
    tunnels.push(tunnelingAgent);

    let oldReq = library.request;
    library.request = function (options, callback) {
        if (tunnels.indexOf(options.agent) != -1 || skipHosts.indexOf(options.host.toLowerCase()) != -1) {
            return oldReq.apply(library, arguments);
        }

        options.agent = tunnelingAgent;
        if (options.port === null) { options.port = isForHttpsRequests ? 443 : 80; }
        if (!options.protocol) { options.protocol = isForHttpsRequests ? 'https:' : 'http:'; }
        
        logger.debug('Tunneling %s %s', options.method, url.format(options) + options.path);
        return oldReq.call(null, options, callback);
    };

    logger.info('Tunneling %s over %s', (isForHttpsRequests ? 'HTTPS' : 'HTTP'), proxyUrl);
}

function getTunnelingAgent(isForHttpsRequests, proxyUrl) {
    if (!proxyUrl) { return undefined; }
    let proxy = url.parse(proxyUrl);

    let options = {
        proxy: {
            host: proxy.hostname,
            port: proxy.port
        }
    };

    let isHttpsProxy = (proxy.protocol == 'https:');
    if (isHttpsProxy) {
        if (isForHttpsRequests) {
            return tunnel.httpsOverHttps(options);
        } else {
            return tunnel.httpOverHttps(options);
        }
    } else {
        if (isForHttpsRequests) {
            return tunnel.httpsOverHttp(options);
        } else {
            return tunnel.httpOverHttp(options);
        }
    }
}