Do I use "the present perfect" or "the past simple" when seeing someone the first time after not seeing them for a while?

Question

Let's say I haven't seen my friend for quite some time. And I am out for a walk. I am going down the street and run into my friend. Do I have to use the present perfect or past simple in this context? For example:

I haven't seen you in ages. Where have you been?

I didn't see you in ages. Where were you?

Logically, I guess, it would correct to use the past simple, because I have met my friend and the fact that I haven't seen him for some time is in the past so the past simple is the tense to go. But, I don't know why the use of it doesn't sound quite right. What do you have to say about it. Which set of sentences sounds the most natural?

Answer 1

You use present perfect, because the time in the past is not specified:

I haven't seen you in ages. Where have you been?

You use past tense when you know exact time in the past, like: " I didn't see you yesterday."

Answer 2

"Where have you been?" means from a moment in the past until this moment in the present, that is why present perfect is appropriate.

I wouldn't use "I didn't see you in ages", I don't think that is correct English. If the moment of meeting again is set in the past, you could say: "when we met again I hadn't seen him in ages". Past perfect tense.