Why do you have a 1000 line function in the first place? Sounds like an entire class of methods in a single structure.

I had a coworker who did similar. It was essentially the entire frontend for an order application (back in the jQuery days), a few thousand lines. That was all copy/pasted, changed to deal with the case of when there are no orders (which only ever happens once since this was an in-house system) and those massive chunks were wrapped in an if/else.

I recently had a junior copy paste a 20 line code block rather than add an extra 'or' to the if statement.

Hey, rule of 3 ;)

Anyways, guidelines are just guidelines, regardless of what you come up with you can break it.