Magento: programmatically invoke "import"

one of the manufacturers uploads daily .xls files to my server , which I then use to automatically detect which products have been added / removed / changed and a .csv import file is generated which I then manually import using System => Import / export => Import (replacing existing complex data) to update products from that manufacturer.

Problem: I need to upload a CSV file and upload it using magento import function. I would like to schedule an automatic daily import of a given CSV file to the Magento store.

Tried it so far: Changing products directly in the database using SQL. It worked, but disadvantages: the code might not work after Magento update, I might throw errors, if my code doesn't update all the information that needs to be updated, I don't get all the error checking that Magento already imported.

Is there a way to import the .csv just like Magento does, but call it programmatically instead of logging into Magento and clicking on import?