Auto gym battling bot - help needed

[HerrStark]

Hi folks!
I've been looking for a specific bot for PokemonGo, and I've heard that this is a good place to ask for some help/guidance
What I am looking for is a bot, that will be able to "sit" still at one location (gym) and start fighing with it when certain player is there, leaving it empty.
My problem is that one gym is constantly being taken by one spoofer with 6 accounts, and well, fight fire with fire works fine for me.

So once again, looking for bot that will be able to perform this actions:
- Sit still at one gym
- If player with username XXX or XYZ or any other is there, fight it
- Leave it empty
- Repeat to infinity

I've been looking ot PokeNinja but still not sure if I can perform this specific task on it, so any tips or suggestions?
I'm familiar with using API, leveling bots etc, not a total newbie here