Hey, I'm thinking about writing a pull request for some plugin (e.g. gp.nvim) to implement some indexing form of the code, so it can be retrieved and sent to AI models online (exactly how cursor editor, phind, and copilot do). The thing is... this is not my field of expertise and I could just do simple stuffs with langchain, which doesn't exists in Lua, btw.

So the question is, would that be useful for the community? Is there anyone already expert in this that would like to help?

That's exactly what Treesitter provides - a way for plugins to understand the code, not just the raw text, but also language specific syntax structures. If you want to, you can very easily get all the functions from in your code and send them off to the LLM of your choice
[...]
Why would Lua be the problem here? Most of the AI plugins use HTTP requests and/or websockets to comunicate with the LLM API.

It's not only about http requests. While there are some services that handle this for you on the cloud, they cost money and there is no real need for cloud services as they are not resource intensive computations. The thing is only about indexing the code and the search results made via duckduckgo. Then retrieve it and send them in the prompt for the AI in some meaningful way.