Battery Problem?

After the big ass rain storm yesterday my battery light was getting brighter and brighter as i drive home from work. But before I reached home and filled up the tank. Paid for my gas and got back into the car, release the handbrake, now my hand brake light or emergency light stays on. Nothing feels different from before just two more shiny red lights on my dash. I put the car in the garage over night and then this morning, start up was fine, then when i tried to punch it, it doesn’t go and idle makes a weird flapping noise. Just now when i tried to start the car again, it tries a lot harder to start up and idling is a lot more quiet now. And idle is still at around 800-1,000 rpm as usual. Could this be because of my battery going to hell, or because of my altenator or just bad grounding?

its an alternator problem…