The latest Definitive Edition of the game actually allows writing code using Ensemble Studios' original scripting language, XS. There are some great docs on it here: https://ugc.aoe2.rocks/general/xs/

The scripting functionalities, such as built-in functions, are still getting expanded with most major updates.

There is also a python-based tool for creating and editing scenarios and triggers via python scripts called AoE2ScenarioParser - and a lot of people are using it as well!

Back in the day, I had so much fun making Red Alert 2 and Age of Empires 2 maps. The whole GUI based triggers/conditions were so frustrating though!

So, I think you just made me lose my weekend.

It uses both. C++14 for the engine, and Python for the convert script and some other things. Check the README for more information.