Proxy module used and written for the SoundCloud mobile project

proxy.js

/**
 * module imports
 */
var _ = require('underscore')._;
var url = require('url');
var http = require('http');
var https = require('https');

/**
 * module exports
 */
exports.Proxy = Proxy;
exports.createProxy = createProxy;

/**
 * Proxy
 *
 * @type {Constructor}
 * @param {Object} config
 * @return {Proxy} New instance of Proxy
 *
 * Examples:
 *
 *      var proxy = proxy.createProxy({
 *        host: 'api.soundcloud.com',
 *        root: '/_api'
 *      });
 */

function Proxy(config) {
    this.config = _.extend({}, this.defaults, config);
    this.replaceRegexp = new RegExp('https?:\/\/' + this.config.host);
}

/**
 * Defaults
 *
 * @type {Object}
 * @param {Number} port Port to connect to on the foreign host
 * @param {String} host Domain or ip address to connect to
 * @param {String} root Location where the proxy is available for local requests
 */
Proxy.prototype.defaults = {
    port: 80,
    host: 'lolcathost.org',
    root: '/_'
};

/**
 * Constructs options object for proxy requests
 *
 * @api private
 * @type {Function}
 * @param {ServerRequest} request nodejs ServerRequest compliant request object
 * @param {Object} opts
 * @return {Object}
 */
Proxy.prototype.proxyOptions = function(request, opts) {
    var options = _.extend({}, this.config, opts);

    options.method = request.method;
    options.path = request.url.replace(this.config.root, '');
    options.headers = _.extend(request.headers, {
        host: options.host
    });

    return options;
};

/**
 * Constructs the location header for redirects
 *
 * @api private
 * @type {Function}
 * @param {ServerRequest} proxyRequest nodejs ServerRequest compliant request object
 * @param {ServerResponse} proxyResponse nodejs ServerResponse compliant response object
 * @return {String}
 */
Proxy.prototype.getLocation = function(proxyRequest, proxyResponse) {
    return proxyResponse.headers['location'].replace(this.replaceRegexp, that.config.root);
};

/**
 * Logic for proxied requests against a foreign host
 *
 * @api private
 * @type {Function}
 * @param {ServerRequest} request nodejs ServerRequest compliant request object
 * @param {ServerResponse} response nodejs ServerResponse compliant response object
 * @param {ClientRequest} proxyRequest ClientRequest compliant request object
 */
Proxy.prototype.request = function(request, response, proxyRequest) {
    var that = this;

    proxyRequest.on('error', function(error) {
        var responseBody = JSON.stringify({
            error: error.message
        });

        response.writeHead(500, {
            'content-length': responseBody.length,
            'content-type': 'application/json'
        });

        response.end(responseBody);
    });

    proxyRequest.on('response', function(proxyResponse) {
        if (proxyResponse.headers && proxyResponse.headers.location) {
            _.extend(proxyResponse.headers, {
                location: that.getLocation(proxyRequest, proxyResponse)
            });
        }

        // XXX hotfix for TLS respones sometimes not fire `end` event
        // issue: https://github.com/joyent/node/issues/728
        // Follow the issue to see a high-level description of the problem

        function endResponse() {
            response.end();
        }
        proxyResponse.on('close', endResponse);
        proxyResponse.on('end', endResponse);

        response.writeHead(proxyResponse.statusCode, proxyResponse.headers);

        proxyResponse.pipe(response, {
            end: false
        });
    });

    request.pipe(proxyRequest);
};

/**
 * Standard interface for proxied requests over http
 *
 * @type {Function}
 * @param {ServerRequest} request nodejs ServerRequest compliant request object
 * @param {ServerResponse} response nodejs ServerResponse compliant response object
 * @param {Object} opts Object with specialized configuration for the current request
 */
Proxy.prototype.http = function(request, response, opts) {
    var options = this.proxyOptions(request, opts);
    var proxyRequest = http.request(options);

    this.request(request, response, proxyRequest);
};

/**
 * Standard interface for proxied requests over https
 *
 * @type {Function}
 * @param {ServerRequest} request nodejs ServerRequest compliant request object
 * @param {ServerResponse} response nodejs ServerResponse compliant response object
 * @param {Object} opts Object with specialized configuration for the current request
 */
Proxy.prototype.https = function(request, response, opts) {
    var opts = _.extend({}, {
        port: 443
    }, opts);
    var options = this.proxyOptions(request, opts);
    var proxyRequest = https.request(options);

    this.request(request, response, proxyRequest);
};

/**
 * Factory for Proxy instances
 *
 * @type {Function}
 * @param {Object} config Configuration for returned Proxy instance
 * @return {Proxy}
 */

function createProxy(config) {
    return new Proxy(config);
}