Definitely an obsession, but it doesn’t sound like psychosis. I have schizoaffective disorder, but I still totally nerd out about things and go through phases where I’m really into something and I wouldn’t call that psychosis. If anything, it’s a pleasant distraction from my psychotic symptoms. Now if you start hearing voices or seeing things that confuse you (that should not be there and maybe scare you about the obsession), then that’s a red flag for psychosis. But it sounds like you don’t have that.