As I see it, it depends on whether you would like to make it real-time or not. If we're talking about Adventure's level of simplicity, you can go the easy way and just check when the player approaches the monster if they have a weapon or not. You can even add some probability to determining whether the strike will hit or miss, and make a simple hit points system. However, it might get a bit more complicated and messy, as you will be dealing with a lot of branching lists within branching lists.
I would say that if you want to use any autonomous movement to the NPC, you will have to use hacks.