how to make a mushroom?

on the mushrooms On Tick Update, have it check for  light level, if too high then pop plant (remove block at x y z, and drop plant item)..the block part, just have it set in the plant type to cave, and for the on tick update, do an If block at x y-1 z is mycelium, allow planting, else pop plant and drop item..

Don't for get to check for air at y+1..

Also, don't forget to have for the On tick update, to randomly grow another mushroom (spawn block x y z) for random x and z axis within a range of the mushroom..

Late response, but how do I check for light level? I can't figure it out for the life of me