I just met a sentence, that is
If someone bought it already, then that item will not show up.
It obviously refers to future, but why is bought used instead of buy?
I consider this same as AFTER, and After you took/after you take? says "You will do this, after you do that,".
I am so confused about this two. Both refer to the future, why is one in the past and the other is in the present?
Because it is looking from the perspective of the point in the future when the item shows up or doesn't. From that point, the buying is in the past (I would say has bought rather than bought, but the choice of present perfect vs past is usually stylistic).
You can tell that it is from that perspective because of the adverb already, which is usually relative to now, or to the temporal focus, rather than to some arbitrary time - in this case, it signals that the temporal focus is after the buying.
You could say If somebody buys it previously, with the same meaning; but to my ear If somebody buys it already does not work.
It's confusing, agreed. The sentence is referring to a metaphorical man and making reference to cause-and-effect of the recent past, then the present. If I bought the apple seller's only apple yesterday, then you wouldn't be able to buy that apple today, because I already have it. It sounds almost like a word problem for the meaning of zero.
