Hypothetically speaking

One has known a certain man for a number of years. Said man is a shy, somewhat awkward and very intense. The sexuality of said man has never been brought up, nor have external events brought it entirely into focus, yet one has assumed since shortly after meeting said man that he is gay and either unaware, in denial or uncomfortable with this fact.
Said man tells one that he is, indeed, gay. Such a confession is clearly a trial for said man, who is, as we mentioned, very shy and intense; what should one’s response be?
‘Ok, that’s cool man’ seems blasé.
‘Yeah, I knew that a while ago’ seems dismissive.
‘WHAT? YOU’RE WHAT??’ seems to be not terribly understanding.

What would one’s reponse be, if you were one?