The concept of Text2Emoji has always excited me. I've done a similar project in Material of Language, one of Allison Parrish's classes, and I visioned creating a chatbot version of the project would allow users to have better access.
To process the incoming message, I made use of RiTa library's toLowerCase() function as shown below. A single line of regular expression has been used to remove any characters other than alphabet letters to prevent further errors.
This is a reference image for the project, presenting emoji equivalent for each letter. If you search for "emoji alphabet," you will encounter more examples of it.
The final set of emoji alphabet used in the chatbot: