Calamity

Calamity is a Haskell library for writing discord bots, it uses Polysemy as the core library for handling effects, allowing you to pick and choose how to handle certain features of the library.

The current customisable effects are:

• Cache: The default cache handler keeps the cache in memory, however you could write a cache handler that stores cache in a database for example.

• Metrics: The library has counters, gauges, and histograms installed to measure useful things, by default these are not used (and cost nothing), but could be combined with Prometheus. An example of using prometheus as the metrics handler can be found here.

Docs

You can find documentation on hackage: here

Example

An example project can be found at: nitros12/calamity-example

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedLabels #-}

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeApplications #-}

{-# LANGUAGE TypeOperators #-}

module Main where

import           Calamity
import           Calamity.Cache.InMemory
import           Calamity.Metrics.Noop

import           Control.Concurrent
import           Control.Concurrent.STM.TVar
import           Control.Lens
import           Control.Monad

import           Data.Text.Lazy              ( Text, fromStrict )
import           Data.Text.Strict.Lens

import qualified DiPolysemy                  as DiP

import qualified Polysemy                    as P
import qualified Polysemy.Async              as P
import qualified Polysemy.AtomicState        as P
import qualified Polysemy.Embed              as P
import qualified Polysemy.Fail               as P

import           Prelude                     hiding ( error )

import           TextShow

data Counter m a where
  GetCounter :: Counter m Int

P.makeSem ''Counter

runCounterAtomic :: P.Member (P.Embed IO) r => P.Sem (Counter ': r) a -> P.Sem r a
runCounterAtomic m = do
  var <- P.embed $ newTVarIO (0 :: Int)
  P.runAtomicStateTVar var $ P.reinterpret (\case
                                              GetCounter -> P.atomicState (\v -> (v + 1, v))) m

handleFailByLogging m = do
  r <- P.runFail m
  case r of
    Left e -> DiP.error (e ^. packed)
    _      -> pure ()

info = DiP.info @Text
debug = DiP.info @Text

tellt :: (BotC r, Tellable t) => t -> Text -> P.Sem r (Either RestError Message)
tellt = tell @Text

main :: IO ()
main = do
  token <- view packed <$> getEnv "BOT_TOKEN"
  void . P.runFinal . P.embedToFinal . runCounterAtomic . runCacheInMemory . runMetricsPrometheusIO
    $ runBotIO (BotToken token) $ do
    react @'MessageCreateEvt $ \msg -> handleFailByLogging $ case msg ^. #content of
      "!count" -> replicateM_ 3 $ do
        val <- getCounter
        info $ "the counter is: " <> showt val
        void $ tellt msg ("The value is: " <> showt val)
      "!say hi" -> replicateM_ 3 . P.async $ do
        info "saying heya"
        Right msg' <- tellt msg "heya"
        info "sleeping"
        P.embed $ threadDelay (5 * 1000 * 1000)
        info "slept"
        void . invoke $ EditMessage (msg ^. #channelID) msg' (Just "lol") Nothing
        info "edited"
      "!explode" -> do
        Just x <- pure Nothing
        debug "unreachable!"
      "!bye" -> do
        void $ tellt msg "bye!"
        stopBot
      "!fire-evt" -> fire $ customEvt @"my-event" ("aha" :: Text, msg)
      "!wait" -> do
        void $ tellt msg "waiting for !continue"
        waitUntil @'MessageCreateEvt (\msg -> (debug $ "got message: " <> showt msg) >> (pure $ msg ^. #content == "!continue"))
        void $ tellt msg "got !continue"
      _ -> pure ()
    react @('CustomEvt "my-event" (Text, Message)) $ \(s, m) ->
      void $ tellt m ("Somebody told me to tell you about: " <> s)