node-http-proxy/lib/http-proxy/passes/web-incoming.js

var http   = require('http'),
    https  = require('https'),
    web_o  = require('./web-outgoing'),
    common = require('../common'),
    passes = exports;

web_o = Object.keys(web_o).map(function(pass) {
  return web_o[pass];
});

/*!
 * Array of passes.
 *
 * A `pass` is just a function that is executed on `req, res, options`
 * so that you can easily add new checks while still keeping the base
 * flexible.
 */

[ // <--

  /**
   * Sets `content-length` to '0' if request is of DELETE type.
   *
   * @param {ClientRequest} Req Request object
   * @param {IncomingMessage} Res Response object
   * @param {Object} Options Config object passed to the proxy
   *
   * @api private
   */

  function deleteLength(req, res, options) {
    if(req.method === 'DELETE' && !req.headers['content-length']) {
      req.headers['content-length'] = '0';
    }
  },

  /**
   * Sets timeout in request socket if it was specified in options.
   *
   * @param {ClientRequest} Req Request object
   * @param {IncomingMessage} Res Response object
   * @param {Object} Options Config object passed to the proxy
   *
   * @api private
   */

  function timeout(req, res, options) {
    if(options.timeout) {
      req.socket.setTimeout(options.timeout);
    }
  },

  /**
   * Sets `x-forwarded-*` headers if specified in config.
   *
   * @param {ClientRequest} Req Request object
   * @param {IncomingMessage} Res Response object
   * @param {Object} Options Config object passed to the proxy
   *
   * @api private
   */

  function XHeaders(req, res, options) {
    if(!options.xfwd) return;

    var values = {
      for  : req.connection.remoteAddress || req.socket.remoteAddress,
      port : req.connection.remotePort || req.socket.remotePort,
      proto: req.isSpdy ? 'https' : (req.connection.pair ? 'https' : 'http')
    };

    ['for', 'port', 'proto'].forEach(function(header) {
      req.headers['x-forwarded-' + header] =
        (req.headers['x-forwarded-' + header] || '') +
        (req.headers['x-forwarded-' + header] ? ',' : '') +
        values[header];
    });
  },

  /**
   * Does the actual proxying. If `forward` is enabled fires up
   * a ForwardStream, same happens for ProxyStream. The request
   * just dies otherwise.
   *
   * @param {ClientRequest} Req Request object
   * @param {IncomingMessage} Res Response object
   * @param {Object} Options Config object passed to the proxy
   *
   * @api private
   */

  function stream(req, res, options) {
    if(options.forward) {
      // If forward enable, so just pipe the request
      var forwardReq = (options.forward.protocol === 'https:' ? https : http).request(
        common.setupOutgoing(options.ssl || {}, options, req, 'forward')
      );
      req.pipe(forwardReq);
      return res.end();
    }

    // Request initalization
    var proxyReq = (options.target.protocol === 'https:' ? https : http).request(
      common.setupOutgoing(options.ssl || {}, options, req)
    );

    // Error Handler
    proxyReq.on('error', function(err){
      var ev   = 'http-proxy:outgoing:web:';
      // If no error listeners, so throw the error.
      if (!options.ee.listeners(ev + 'error').length){
        throw err;
      }
      // Also emit the error events
      options.ee.emit(ev + 'error', err, req, res);
    });

    req.pipe(proxyReq);

    proxyReq.on('response', function(proxyRes) {
      var ev   = 'http-proxy:outgoing:web:';

      options.ee.emit(ev + 'begin', req, res);

      // When the previous request respond, we apply the
      // outgoing passes to the response
      web_o.some(function(pass) {
        var evnt = ev + pass.name.toLowerCase() + ':', val;

        options.ee.emit(evnt + 'begin', req, res);
        // Call the pass with the proxy response
        // pass(ClientRequest, IncomingMessage, proxyResponse)
        val = pass(req, res, proxyRes);
        options.ee.emit(evnt + 'end');

        return val;
      });

      options.ee.emit(ev + 'end');


      proxyRes.pipe(res);
    });

    //proxyReq.end();
  }

] // <--
  .forEach(function(func) {
    passes[func.name] = func;
  });