pass-thru-middleware.js

var rendrMw = require('rendr/server/middleware')
  , _ = require('underscore')
;

module.exports = function(dataAdapter, method, options) {
  return function(req, res, next) {
    if (req.path !== options.appPath && req.method !== method.toLowerCase()) return;
    
    res.format({
      json: function() {
        // pass to apiProxy
        // make the `path` look like it would in a normal request to /api/-/users/authorize
        var proxyReq = _.clone(req);
        proxyReq.path = options.apiPath;
        rendrMw.apiProxy(dataAdapter)(proxyReq, res, next);
      },
      html: function() {
        // make request using dataAdapter
        // maybe instead of hardcoding path, could reuse i.e. User model.
        var spec = {
          path: options.apiPath,
          method: method
        };
        dataAdapter.request(req, spec, function(err, response, body) {
          if (response.status === 400) {
            res.redirect(options.appPath + '?error=' + body.error);
          } else {
            res.redirect(options.successRedirect);
          }
        });
      }
    });
  };
};

// usage

var passThruMiddleware = require('./middleware/passThruMiddleware').bind(null, dataAdapter);

app.use(passThruMiddleware('POST', {
  appPath: '/login',
  apiPath: '/users/authorize',
  successRedirect: '/dashboard',
));

pass-thru-post.js

var rendrMw = require('rendr/server/middleware')
  , dataAdapter = require('./dataAdapter')
  , _ = require('underscore')
;

app.post('/login', function(req, res, next) {
  res.format({
    json: function() {
      // pass to apiProxy
      // make the `path` look like it would in a normal request to /api/-/users/authorize
      var proxyReq = _.clone(req);
      proxyReq.path = '/users/authorize';
      rendrMw.apiProxy(dataAdapter)(proxyReq, res, next);
    },
    html: function() {
      // make request using dataAdapter
      // maybe instead of hardcoding path, could reuse i.e. User model.
      var spec = {
        path: '/users/authorize',
        method: 'post'
      };
      dataAdapter.request(req, spec, function(err, response, body) {
        if (response.status === 400) {
          res.redirect('/login?error=' + body.error);
        } else {
          res.redirect('/dashboard');
        }
      });
    }
  });
});