SAP Idoc data in ,txt file to SFTP external server

Dear Experts,

Thank you for the useful points.

I have mentioned below steps on how I am planning for the implementation. Please correct me if am wrong here. as I am new to Idoc EDI.

The exact requirement is - Any invoices generated in SAP has to be converted into EDI X12 text file from idoc messages and same need to be placed on external SFTP server . There may be instance we may also need to process invoice from past date as well. As of we have only 1 customer and its a once in a Month activity.

1. How we can generate Idoc message for a invoice, the moment it got created in SAP ? Is there any standard way of doing it OR we have do it through a custom ABAP program ? Please advise.

2. We may also need to generate Idoc message for a invoice in past date also post go-live. How we can achieve this. A custom ABAP program will suffice ? Please advice

If yes, Can we write a custom ABAP program to generate Idoc messages for any new invoice generated in SAP and also for the past dated invoices and schedule it in batch job ? Please advice

3. A user interface deployed on FIORI which will have selection inputs for 'Customer & Invoice Period'. On executing, the program should fetch all generated Idoc numbers from the scheduled batch job log table and convert it into EDI X12 text file format. ABAP program will convert. (Understood & under development)

4. Upload the same file on external SFTP folder & not FTP ? How we can achieve this ? I tried searching in the forum but couldn't find any. We will be using SFTP and not FTP ? Please advise.

Requesting your helpful inputs.

Thanks, Sharda