firebase-tools/lib/hostingInitMiddleware.js

'use strict';

var request = require('request');

var SDK_PATH_REGEXP = /^\/__\/firebase\/([^/]+)\/([^/]+)$/;

module.exports = function(init) {
  return function(req, res, next) {
    var match = req.url.match(SDK_PATH_REGEXP);
    if (match) {
      var url = 'https://www.gstatic.com/firebasejs/' + match[1] + '/' + match[2];
      var preq = request(url).on('response', function(pres) {
        if (pres.statusCode === 404) {
          return next();
        }
        return preq.pipe(res);
      });
    } else if (req.url === '/__/firebase/init.js') {
      res.setHeader('Content-Type', 'application/javascript');
      res.end(init.js);
    } else if (req.url === '/__/firebase/init.json') {
      res.setHeader('Content-Type', 'application/json');
      res.end(init.json);
    } else {
      next();
    }
  };
};