[guizzy]

A computer would only win by playing out pre-proved positions (joseki) against an amateur who has studied them positions without understanding them.

As for infinite games, they don't really happen much; in rulesets that make it possible for them to happen, the game is usually called "no result", and this has happened only very few times in hundreds of thousands of recorded games. Modern rulesets have "patched out" this by implementing superko or similar rules: playing a stone that would put the board in a state it was in previously (positions of the stones and which player's turn it is) is an illegal move.