Light fixture to bath vent wiring

Hello, I currently have a light fixture set up with a ceiling fan tied into the junction box the light fixture is attached to. The main electrical can only reach a little past the light fixture but I wanted to put in a new bath fan above the shower. Is it acceptable and does it meet code to use the junction box the light is on to run longer wire to where I want the bath fan or does this not meet code?

If it does not meet code I am just going to remove the light and use just a bath fan with light as close to the shower as I can get it, unless there is another way to do this with minimal mess.

In picture below I want to leave light there and put new fan in directly above shower by tying into the JBOX the light is on.