I have an exposed conduit switch box on my front porch that controls a spotlight. I would like to add a gfci outlet to the switch box (swapping the switch box for a double box thst is weatherproof) The switch seems to be a 3 way switch but the wiring does not match what I have read for either a single pole or a three way shared switch circuit. And as far as I can tell there is only one switch for this light (inconveniently located on the front porch). I do not know if the power goes to the light or switch first.
Switch has one side with a dark screw and a gold screw, then the other side has a second gold screw opposite the first, and a blank space opposite the dark screw. There is also a ground screw.
In the switch box is one run with black white and bare wires. Black goes to the dark screw "top" of the switch, white goes to gold screw on the opposite side and bottom of the switch from black. Bare is attached to the ground screw.
In one position all the black, white and empty gold screw are not hot, in the other switch position the black and empty (same side as each other) are hot but the white is not (using a noncontact voltage sniffer).
In the light box there is also one lead (pigtailed to two spotlights) Is it possible to add the gfci?