"Are you staying long?" Whom do you ask that question? a person going or a person coming

Question

"Are you staying long?"   Whom do you ask that question?   a person going or a person coming

Answer

A person that is coming or has already arrived. 
If it was a person that was going to come I would say 'will you' or are you going to  be' staying long?'

But yours is easy to use in both situations

Answer

It would not matter. The question could be asked of either.