Mongoose - FindOne() inside Multer - express

Question

I am sending formData to my express app like so:
itemFactory.saveItem = function(item, callback){
var formData = new FormData();
for(var i = 0; i < item.photos.length; i++){
formData.append('photos', item.photos[i]);
}
for(var key in item){
formData.append(key, item[key])
}
return $http.post('/api/item/', formData, {
transformRequest: angular.identity,
headers: { 'Content-Type': undefined }
}).success(callback);
};
I am saving a new item to my mongoose DB. Now everything is working perfectly. But I want to detect duplicates using mongoose findOne(), and not just let mongoose handle detecting if a duplicate key exists when writing to the DB. Because my images get uploaded regardless at this stage, if a duplicate key exists or not. Because it only detects the duplicate on save()
The problem now, in my express app, is when I am using findOne(), Multer() has not yet decoded my formData. ex:
router.post('/item', function(req, res){
Vehicle.findOne({ id: String(req.body.id) }, function(error, item){
var storage = multer.diskStorage({...})
var upload = multer({
storage: storage
}).any();
upload(req, res, function(error){
//formData is only available here via req.body
//and not at findOne() stage.
});
});
});
I cannot do the findOne inside the upload because then the files would be uploaded anyway and then only detect a duplicate.
I tried another multer().any() function for getting the formData just after the .post() but that did not seem to work. I don't think I can do this:
var detectItem = multer().any()
detectItem(req, res, function(){
Vehicle.findOne({ id: String(req.body.id) }, function(error, item){
var storage = multer.diskStorage({...})
var upload = multer({
storage: storage
}).any();
upload(req, res, function(error){
//formData is only available here via req.body
//and not at findOne() stage.
});
})
It does not seem to like me using a multer function inside a multer function.
Any advice?

Answer 1

You can use fileFilter option to control which files are accepted.
It could be something like this:
function filFilter (req, file, cb) {
Vehicle
.findOne({ id: req.body.id })
.then(item => {
cb(null, !item); // Skip if item exists (passing false skips file)
})
}

Answer 2

You could separate them into two middlewares
app.post('/item', function(req, res, next){
//this middleware is used to check duplicate
Vehicle.findOne({id:req.body.id}).then(function(item){
if(item) res.end() //if item existed, send response directly
else next() //if item not existed, continue to next middleware
})
}, function(req, res){
var storage = multer.diskStorage({...})
var upload = multer({ storage: storage }).any();
upload(req, res, function(error){
// ...
});
})