Referencing multiple collections within MongoDB - mongodb

Question

I have three collections in my Database: Apps, Reviews, and Users.
Apps will have multiple reviews, reviews will have one user, and users will have multiple reviews.
I do need them all tied together and am struggling. I have been able to attach reviews to users (and vice versa), but I am unable to attach the reviews to the apps. I was thinking this action needs to happen on the POST to the database for a review.
I do have the appId required (and it's stored within the review body), but I am unable to correctly identify and update the correct collection (applications) in the database. I seem to be spinning myself in circles over this.
Basically, I need to reference both the Application the review is for, and the User who reviewed when a review is posted. I do have all models "correctly" referencing the other collections (as you demo'd with your messages and users components).
Would anyone be able to point me in the right direction? Here is my code for the POST so far.
// SAVE A REVIEW TO DATABASE
router.post('/', function(req, res, next) {
var decoded = jwt.decode(req.query.token);
User.findById(decoded.user._id, function(err, doc) {
if (err) {
return res.status(404).json({
title: 'An error occurred',
error: err
});
}
var review = new Review({
content: req.body.content,
rating: req.body.rating,
app: req.body.appId,
user: doc
})
Application.findById(req.body.appId, function(err, doc) {
if (err) {
return res.status(404).json({
title: 'An error occurred',
error: err
});
}
review.save(function(err, result) {
if (err) {
return res.status(404).json({
title: 'An error occurred',
error: err
});
}
review.update(function(err, result) {
if (err) {
return res.status(404).json({
title: 'An error occurred',
error: err
});
}
doc.reviews.push(result);
doc.save();
res.status(201).json({
message: 'Saved review',
obj: result
});
});
});
});
MODELS:
Review Model:
var schema = new Schema({
content: {type: String, required: true},
rating: {type: Number},
dateCreated: {type: String},
app: {type: Schema.Types.ObjectId, ref: 'Application'},
user: {type: Schema.Types.ObjectId, ref: 'User'}
});
Application Model:
var schema = new Schema({
name: {type: String, required: true},
description: {type: String},
reviews: [{type: Schema.Types.ObjectId, ref: 'Review'}],
})
User Model:
var schema = new Schema({
firstName: {type: String, required: true},
lastName: {type: String, required: true},
password: {type: String, required: true},
passwordConfirm: {type: String, required: true},
email: {type: String, required: true, unique: true},
reviews: [{type: Schema.Types.ObjectId, ref: 'Review'}]
});
Perhaps I am going the way wrong way about this, but I seem to be pretty lost.
Thank you everyone in advance.