NodeJs - calling one method from another in server controller - node.js

Question

With the following controller, how can I call one method from another in the same controller?
Specifically, calling login() within a successful signup(), while retaining the same functionality for login() when it is used by a form?
The line this.login(newUser) does not work, nor does plain old login(newUser)
In both scenarios, I get the error:
TypeError: Cannot call method 'login' of undefined
var mongoskin = require('mongoskin');
module.exports = {
login: (function (req, res) {
req.db.collection('auth').findOne({_id: mongoskin.helper.toObjectID(req.body.id)},
function (err, results) {
// log person in and send results to client
}
)
}),
signup: (function (req, res) {
var user = req.body;
req.db.collection('auth').insert(user, function (err, newUser) {
// after adding user, automatically log them in
// does not work:
//login(newUser, function (err) {
// do something
//})
// does not work:
this.login(newUser, function (err) {
// do something
})
}
)
})
}

Answer 1

Controllers should be doing as little as possible, and should orchestrate the work required by executing functions stored elsewhere.
View this gist - click here
What I have done is created "services" that are not tied to the client request, therefore re-usable everywhere.
Hope this helps.

Answer 2

Thanks to Dave Newton
var mongoskin = require('mongoskin');
var myCollection = 'auth';
Solution
function localLogin(db, myCollection, user, res){
db.collection(myCollection).findOne({_id: mongoskin.helper.toObjectID(user._id)},
function(err, user){
res.send({ token: createToken(user) });
});
module.exports = {
login: (function (req, res) {
var user = req.body;
localLogin(req.db, myCollection, user, res)
},
signup: (function (req, res) {
var user = req.body;
req.db.collection(myCollection).insert(user, function (err, newUser) {
// after adding user, automatically log them in
localLogin(req.db, myCollection, newUser, res)
})
}
) }) }