{-# LANGUAGE OverloadedStrings #-}  -- allows "string literals" to be Text
import           Control.Monad (when, void)
import           UnliftIO.Concurrent
import           Data.Text (isPrefixOf, toLower, Text)
import qualified Data.Text.IO as TIO

import           Discord
import           Discord.Types
import qualified Discord.Requests as R

-- | Replies "pong" to every message that starts with "ping"
pingpongExample :: IO ()
pingpongExample = do
    userFacingError <- runDiscord $ def
             { discordToken = "Bot ZZZZZZZZZZZZZZZZZZZ"
             , discordOnEvent = eventHandler
             , discordOnLog = \s -> TIO.putStrLn s >> TIO.putStrLn ""
             } -- if you see OnLog error, post in the discord / open an issue

    TIO.putStrLn userFacingError
    -- userFacingError is an unrecoverable error
    -- put normal 'cleanup' code in discordOnEnd (see examples)

eventHandler :: Event -> DiscordHandler ()
eventHandler event = case event of
    MessageCreate m -> when (isPing m && not (fromBot m)) $ do
        void $ restCall (R.CreateReaction (messageChannelId m, messageId m) "eyes")
        threadDelay (2 * 10^6)
        void $ restCall (R.CreateMessage (messageChannelId m) "Pong!")
    _ -> return ()

fromBot :: Message -> Bool
fromBot = userIsBot . messageAuthor

isPing :: Message -> Bool
isPing = ("ping" `isPrefixOf`) . toLower . messageContent