Nested insert in Mongodb with Node.js - node.js

Question

I'm receiving a CSV file which contains a list of products. Each product has a category. When I save a product I have to find if the category already exists in the database and if it does not I have to create it (and save it) before saving the product.
module.exports.do_import = function (req, res) {
var final_json = {};
fs.createReadStream(req.files.file.path)
.pipe(csv({
separator: ';'
}))
.on('data', function (data) {
mongoose.model("Category").findOne({nombre: data.NOMBRE}, function (err, category) {
if (category == null) {
var created_category = new Category({nombre: data.NOMBRE});
created_category.save(function (err, __category) {
var product = new Product({
nombre: data.NOMVDA,
categoria: __category,
codigo: data.CODVAR
});
product.save(function (err, prod) {
if (err) {
final_json.success = false;
res.json(final_json);
}
});
});
} else {
var product = new Product({
nombre: data.NOMVDA,
categoria: category,
codigo: data.CODVAR
});
product.save(function (err, prod) {
if (err) {
final_json.success = false;
res.json(final_json);
}
});
}
});
}).on('finish', function () {
final_json.success = true;
}).on('error', function () {
final_json.success = false;
}).on('end', function () {
res.json(final_json);
});
So, the trouble I've got here is that the .save() function of the category is executed asynchronously, so when the next record of the file is requested, the category of the previous one isn't saved yet, so it creates a the same category twice. How can I make the function wait until the save operation is completed?

Answer 1

Finally a friend of mine help me and thanks to this https://nodejs.org/api/stream.html#stream_readable_pause we can make the flow stop until the product has already been created.
Here is the final code:
module.exports.do_import = function (req, res) {
var final_json = {};
var readable = fs.createReadStream(req.files.file.path)
.pipe(csv({separator: ';'}));
function saveErrorHandler(err, prod) {
if (err) {
final_json.success = false;
res.json(final_json);
}
readable.resume();
console.log('next category');
}
readable.on('data', function (data) {
console.log('data');
readable.pause();
console.log('pausa');
mongoose.xmodel("Category").findOne({nombre: data.NOMBRE}, function (err, category) {
// Manejá el error que no lo tenes.
if (category) {
// esto se podría sacar ya que esta duplicado, pasale la categoría a una función
var product = new Product({
nombre: data.NOMVDA,
categoria: category,
codigo: data.CODVAR
});
product.save(saveErrorHandler);
} else {
var created_category = new Category({nombre: data.NOMBRE});
created_category.save(function (err, __category) {
var product = new Product({
nombre: data.NOMVDA,
categoria: __category,
codigo: data.CODVAR
});
product.save(saveErrorHandler);
});
}
});
});
readable.on('finish', function () {
final_json.success = true;
});
readable.on('error', function () {
final_json.success = false;
});
readable.on('end', function () {
res.json(final_json);
});