ulyssesdotcodes/linklater

The premier Haskell library for writing Slack bots

Who let you in here?

Relax! I'm here to make your life easier. Has your company ever switched to using Slack, and then you wanted to write silly Slack bots in Haskell as a way to learn Haskell?

^{Really?WowThat was a pretty specific question.}

Uh, do you want to be friends? Well let's talk about it later, because right now I have an example for you.

But you'll have to grab me first:

• cabal sandbox init
• cabal install linklater

If you don't have Haskell, it's quite easy: Windows, Mac, and Linux.

Show me an example!

Here's a /jpgto bot. If you run this program and then tell Slack about your server (incoming hook and custom slash command) and then type /jpgto baby corgi in one of your channels, you'll get the image from http://baby.corgi.jpg.to. How, you say? Screen scraping.

-- Remaining imports left as an exercise to the reader.
import Network.Linklater (say, slashSimple, Command(..), Config(..), Message(..), Icon(..), Format(..))

findUrl :: Text -> Maybe Text
findUrl = fmap fromStrict . maybeResult . parse (manyTill (notChar '\n') (string "src=\"") *> takeTill (== _quotedbl))

jpgto :: Maybe Command -> IO Text
jpgto (Just (Command user channel (Just text))) = do
  message <- (fmap messageOf . findUrl . decodeUtf8 . flip (^.) responseBody) <$> get ("http://" <> (unpack subdomain) <> ".jpg.to/")
  case (debug, message) of
    (True, _) -> putStrLn ("+ Pretending to post " <> (unpack . decodeUtf8 . encode) message) >> return ""
    (False, Just m) -> config' >>= say m >> return ""
    (False, Nothing) -> return "Something went wrong!"
  where config' = (Config "trello.slack.com" . filter (/= '\n') . pack) <$> readFile "token"
        subdomain = (intercalate "." . fmap (filter isLetter . filter isAscii) . words) text
        messageOf url = FormattedMessage (EmojiIcon "gift") "jpgtobot" channel [FormatAt user, FormatLink url (subdomain <> ".jpg.to>")]
        debug = True
jpgto _ = return "Type more! (Did you know? jpgtobot is only 26 lines of Haskell. <https://github.com/hlian/jpgtobot/blob/master/Main.hs>)"

main :: IO ()
main = let port = 3000 in putStrLn ("+ Listening on port " <> show port) >> run port (slashSimple jpgto)

For the full example (since this one is missing a ton of imports), see the examples/ directory on GitHub.

Now! /jpgto baby corgi:

So easy. Much fast.

Features

• Uses 'Text' for state-of-the-art Unicode support;
• Lovely documentation with no misspelllllings to be found;
• Supports [Slack's formatting syntax](https://api.slack.com/docs/formatting Slack's formatting syntax)
• Comes with a fast mode (slashSimple) and a power mode (slash)
• A warm, receptive maintainer with beautiful brown eyes;
• Fully Haddock'd methods and module;
• Open source (BSD3).

Contributors

• Hao Lian, author
• Ian Henry, design review and future contributor???
• Shields (the Grizzly Bear album), which I listened all the way through for the first time while I was writing this ★★★★