That's what I want to know. I hear a new voice with this one. You sound like a nice Gramma.
It seems a little strange to ask a friend who he or she is.
if I want to say "who are you, a friend"?, instead of "who are you, friend"? how it'll be?
a charaid means both "friend" and "a friend", so you just say "co thusa, a charaid?" (of course with the accents)
It makes "who are you?" Less intimidating, and nicer than "who are you, stranger"