Nice, but as an advice I prefer to separate API from Server callbacks. That means putting handle info, init down in your code with server callbacks 
Also…
new_state = my_state ++ [value]
# I would use, which is not the same...
# but i would push at the head of a list, and maybe reverse later.
new_state = [value | my_state]
# Also
case do end... could also be if do else end...
