Well, that doesn't scale at all. I don't remember the last time I've worked on a project where even skimming all of the code would be possible in a reasonable

Well, that doesn't scale at all. I don't remember the last time I've worked on a project where even skimming all of the code would be possible in a reasonable amount of time, much less actually reading it and refactoring it. That said, it probably does scale to the OP's 8k line code base. Also, running the code through a formatter and refactoring it all right off the bat is a sure fire way to piss off everybody else working on the project. In any case, my 2 cents for the OP is to not bother trying to learn the whole codebase, but instead focus on just the areas you want to enhance. For example, in the case of the new data source, find out how the existing data sources are implemented, and use them as examples for adding a new one.