It actually turned out to be easier than I thought.

The infrared reader (arduino code) is based on

github.com/Arduino-IRremote/Arduino-IRremote

The code running on my raspberry pi was written in Java using spring boot which is probably overkill but I am more comfortable with java than python so I used

github.com/Fazecast/jSerialComm

to read data from the pi’s usb port and just sent instructions to the unified remote server which does most of the heavy lifting. I used

github.com/…/UnifiedRemoteConnection.java

as a reference along with some verbose logging on the unified remote server to see what codes needed to be sent over the rest api.