The victim was attempting to de-escalate the situation when he was hit in the back of the head with a heavy glass beer jug, knocking him to the ground unconscious.
"He is currently in an induced coma and is in a very serious condition.
"CCTV footage of the assault helped us identify a person of interest and today, a 23-year-old man will appear in the Hamilton District Court charged with wounding with reckless disregard."
Mr Greene said investigators had spent the weekend conducting a scene examination and interviewing witnesses.
Police are appealing to any witnesses to the attack to come forward with information.
"While unable to speak to specifics about this case as it is before the courts, Friday's incident highlights the need for those holding work functions to ensure there are non-alcoholic alternatives available and the importance of ensuring steps are in place to get everybody home safely."