Is it possible to set the brighness of a light from a variable in Apple HomeKit

Question

I want to create a wake up light with Apple HomeKit Automations that gradually increases the brightness of an Apple HomeKit controlled lightbulb. A simple while-loop as written in a following pseudo code should do the trick:

/* This automation is run every morning at 9 AM when all the lights are off */

var = 0
While var < 100:
    var = var + 1
    set_light_x_brighness(var)
    wait 10 seconds

For now it seems that the Apple HomeKit lacks the possibility to set the brightness of a HomeKit controlled lamp from a variable. Any ideas to circumvent this?