How do I trigger data to be sent from our third-party application to NetSuite - api

Question

I am trying to do an API integration of our third party application with NetSuite. I want to be able to import sales invoice details generated from our third party system (which uses REST API) into the NetSuite invoice form.
The frequency of import is not too crucial- an immediate import will be ideal, but sending data once a day is fine as well.
Furthermore, the invoice on NetSuite needs to be filled with details of which some are already available on NetSuite (ex: tax code, billing address, etc.) and some which need to be imported from the third party application (ex: item name, price, etc.)
How would I go about doing so? Would I need to use our API to get the item and price details, use an API to get the details from NetSuite, merge them together somehow and push that into NetSuite? Is there a less complex way of doing so?
I have heard of user events that trigger when a change occurs on NetSuite, and scheduled scripts that trigger every x period of time, but I have only seen these being used from the POV of sending data FROM Netsuite into a third party system. How would I trigger data to be sent to NetSuite when an invoice is created on our external application?
To summarize, I would like to know how to go about integrating when data is needed from 2 sources (NetSuite itself, and the external application) and how to trigger the data to be imported into NetSuite.
I am a complete beginner to APIs and NetSuite. Tips on what I should look into researching, and any/all help is much appreciated!

Answer 1

In my opinion, the easiest way to implement what you need here, is to use a NetSuite scheduled script to GET the data from the third party API, and then create the invoices required from that data. Instead of thinking about it as the third party application sending data to NetSuite, think about it as NetSuite fetching the data from the third party application.
The scheduled script would need to connect to the third party, authenticate and run a query to get any new invoices using whatever filters make sense (for example, 'date created'). It would then need to iterate over the records returned to create corresponding records in NetSuite.
Scheduled scripts can be set up to run on schedule at any time interval down to 15 minutes, or can be called from another script using the N/task module. They can also be triggered manually for testing.

Answer 2

You can use the Scheduled Script if you are fine with running batch processes at set intervals to pull in updates from the 3rd party, and the third party application has the necessary REST API (or gives you the ability to create new ones). You will need to create a mechanism to only ask for new/updates from a cutofftime and maintain that in NetSuite to avoid pulling in the same data each time.
If you want the third party application to push the data in realtime to NetSuite, you would need to write some code on the 3rd party app that either triggers on specific events (or is timed like the first approach). This can then call a custom RESTLET you would create on NetSuite, and pass along all the information NetSuite needs {itemname, price, etc} in JSON format. The RESTLET code would take the JSON data, add the missing pieces it needs to source from NetSuite objects{taxcode, billing address, etc} and create the invoice. Depending on your design, you could also have it such that the JSON could be a single invoice, or a list of invoices that you club together for performance.
Finally, you may also want to look at iPAAS platforms like Dell Boomi, Celigo, Jitterbit, etc. All of these support NetSuite as one of their endpoints. If they also natively support the 3rd party application you are using, you could achieve your objective with far less coding. All these platforms also support connecting to a REST API though.