Ask HN: Please help me find a sci-fi novel

I have seen it a couple of years ago on HN. It's about a person with a brain tumor, who get's treated with an experimental treatment, that infects the tumor with a virus. Once they kill that part off with an anti-viral treatment she is deemed healed. Unfortunately as a side-effect the treatment removes all the parts responsible for joy too and leaves her in a deep apathy, until one day she receives a interface to stimulate her brain and effectively choose how much joy she feels in a given moment. Then the story goes on showing how she tries to tune this interface.