Night camera effect

I’m trying to define a post processing material to mimic the behavior of a night camera. To make it short I need a camera that under a certain condition of lighting (sunlight or good lighting) behave like a normal color camera but when the environment get dark it switch to a grayscale camera (maybe with some noise over it). Is it possibile to define all this trough a single post processing material?
I know how to desaturate to get camera to grayscale but I don’t know how to bind it to the environment lighting condition.
Another issue is how to enanche the camera sensivity when the environment darken… is it possible?

Best regards,