What does ワインを買っていくよ mean?


I am very confused about the meaning of the expressions 'ていく' and 'てくる' and
seems that every website I look has a different explanation.

Translations that I think are good:  
_'Go in order to buy wine';  
'Going to buy wine';  
'Buy a bottle of wine and then go'._  
Which one is right and why?




> ワインを買っていく

literally means "I'll buy wine and go". You'd say this to mean "I'll buy wine
on my way to the place where you are (≂ I'll buy wine and bring it to the
place where you are)", "I'll buy wine on my way to somewhere (away from the
hearer) (≂ I'll buy wine and bring it to somewhere (away from the hearer))",
or "I'll buy wine here(, and leave this place)."

Compare:

> ワインを買いに行く "I'll go (somewhere) to buy wine."
>
> ワインを買ってくる "I'll buy wine (somewhere) and come back (here; to the place where
> the speaker is now)."




> ワインを買っていく

literally means "I'll buy wine and go". You'd say this to mean "I'll buy wine
on my way to the place where you are (≂ I'll buy wine and bring it to the
place where you are)", "I'll buy wine on my way to somewhere (away from the
hearer) (≂ I'll buy wine and bring it to somewhere (away from the hearer))",
or "I'll buy wine here(, and leave this place)."

Compare:

> ワインを買いに行く "I'll go (somewhere) to buy wine."
>
> ワインを買ってくる "I'll buy wine (somewhere) and come back (here; to the place where
> the speaker is now)."

