It occurred around 7.25 p.m. on Tuesday, July 12th, outside the Tesco Express on Keighley Road.
The victim, a 55-year-old man, was taken to the hospital with a serious head injury and is said to be in stable condition.
A 36-year-old man arrested on suspicion of assault was released on bail pending further investigation.
Detectives are looking for anyone who witnessed what happened, particularly a woman in a pink top who was walking her dog in the area at the time of the incident.
Anyone with information about this case is asked to call Calderdale CID at 101 or use the LiveChat feature on the West Yorkshire Police website.
The case number is 13220379205.
Anonymous information can also be reported to the independent charity Crimestoppers by calling 0800 555111 or going online.
