You are not only one trying to do it. There are others, and in other programming languages (Pokemon Showdown is one already implemented, but uses TypeScript with dependencies and I wanted to avoid those issues). What programming language did you intend to use?

I intended to do as a C library (which would then be available for other programs in C to call). I know many of the rules of Pokemon but not all of the cases, and then, knowing the data structures to make, etc. I also wanted to make the rules customizable (and to implement all generations, although perhaps only some of them will be implemented the first time and others later) and I have some ideas about that.

I would hope that some people can work on something together.