RpsBot

A Telegram Bot for playing Rock-Paper-Scissors written in Scala.

It uses Canoe for the Telegram integration (not Canoe's Scenario DSL though).

This is my first project trying the "purely functional" way of scala and using an abstract effect type described by cats typeclasses.

Try it out

For testing, if you want to spin up a bot in another language or with a different wording, you can simply build new implementations for rpsbot.bot.communication.operations.UserMessageParser and rpsbot.bot.communication.operations.FeedbackTranslator and create your bot application as an fs2 Stream using rpsbot.bot.RpsBotApp.create as in rpsbot.Boot (or simply change the lazy val interaction in Boot). You can find information on how to create a Telegram Bot and obtain its token in the Telegram Bot Api Documentation. You need a DynamoDB table (or local stack) or use the in memory storage implementation.

If you are also getting into this way of scala programming and are trying to understand the application, I recommend checking out rpsbot.bot.communication.UserMessageHandler which contains the core "business logic" of the application, and then retracing how it is used in rpsbot.bot.RpsBottApp.create which is called by rpsbot.Boot, the entrypoint to an example application.

If you are on the other hand very experienced with cats/fs2/purely functional programming and have some advice, please feel free to message me or open an issue. :)

TODOs

• The method signatures of the Storage trait do not reflect the fact that something could go wrong at runtime (like a non-reachable database in case of persistent storage) and, subsequently, the implementations ignore possible errors by dangerously calling .get and the likes, which might cause the application to crash at runtime.

• Storage is also tightly coupled to RPS because one of the parameters of Storage.updateMatch is of type rpsbot.rps.model.Match. This could be prevented by making Storage polymorphic in the Match type, i.e. adding a type parameter M to the trait (so that it's Storage[F[_], M]) and updating the method to def updateMatch(lobbyId: Int, updatedMatch: M, timestamp: Int): F[Lobby]. When going down that road, one might also decouple the UserMessageHandler from RPS completely, making it into something like a generic "Lobby- and Game-Move-Handler for 2 Player Games playable by sending texts to a Telegram Bot", which seems like a great example for overengineering but also like an interesting exercise so I might do that in the future.

In Action (unless currently offline)

Sometimes, you can find a running German version of the bot at https://telegram.me/DerSchnickBot. The name, like the command to create/join lobbies as found in rpsbot.MessageParserDE, stems from "Schnick Schnack Schnuck", one of the more common names of the many names the game has in German. [1]