I have already made a chatbot on slack that was automating food ordering, the client was giving the bot a url for a restaurant, the bot then crawels that url that should contain a menu, gets all items and prices, show them as drop downs in the chat for all other users in the channel, after a certain period set by the order initiator the chatbot collects all orders, asks the users for credentials, confirmation and places the order automatically.
the previous chat bot was also made to work on google hangouts.
I also made a chat bot on messenger.
I am asuming that a chat bot on whatsapp would not be of a big difference than those I already made, just a different API by whatsapp.