Network.Linklater

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 (== '"'))

 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>"), FormatString "no way!: &<>"]
         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)

One /jpgto baby corgi, et voila.

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

https:github.comhlianlinklater

Documentation

say :: Message -> Config -> IO (Response ByteString)

The say function posts a Message, with a capital M, to Slack. It'll, however, need a Config (a.k.a. incoming token) first.

slash :: (Maybe Command -> Application) -> Application

A bot server! As if by magic. This acts like a WAI middleware: Linklater wraps around your application. (Really, it just gives you a Command to work with instead of a raw HTTP request.)

slashSimple :: (Maybe Command -> IO Text) -> Application

A bot server for people who are in a hurry. Make a function that takes a Command and returns some Text in IO world, and we'll convert it into a WAI application. If you want more control over the request and respond, see slash.

data Channel

Where slash commands come from, and where Messages go.

Constructors

GroupChannel Text

A public or private group.

IMChannel Text

A private conversation with your best friend -- or lover ;).

Instances

Eq Channel

Ord Channel

Show Channel

newtype User

A username: no at-signs, just text!

Constructors

User Text

Instances

Eq User

Ord User

Show User

data Message where

Here's how you talk: you make one of these and pass it to say. Before the day is done, Linklater will convert this to a JSON blob using Aeson.

• Simple messages are parsed by Slack with parse=full (i.e. as if you had typed it into the input box).
• Complex messages are parsed according to Slack formatting. See Format.

Constructors

SimpleMessage :: Icon -> Text -> Channel -> Text -> Message

FormattedMessage :: Icon -> Text -> Channel -> [Format] -> Message

Instances

ToJSON Message

data Config

Like a curiosity about the world, you'll need one of these to say something.

Constructors

Config

Fields

_configHostname :: Text

This is where your Slack account is hosted. For example, trello.slack.com.

_configIncomingHookToken :: Text

This is the incoming web hook token that Slack gave you. It's usually a long alphanumberic string of garbage.

data Command

Incoming HTTP requests to the slash function get parsed into one of these babies.

Constructors

Command

Fields

_commandUser :: User

Who ran your slash command.

_commandChannel :: Channel

Where the person ran your slash command.

_commandText :: Maybe Text

Text for the slash command, if any.

Instances

Eq Command

Ord Command

Show Command

newtype Icon

The icon next to the messages you say. (Images unsupported right now, sorry.)

Constructors

EmojiIcon Text

For example, :stars2:.

Instances

Eq Icon

Ord Icon

Show Icon

data Format

A little DSL for Slack formatting.

Constructors

FormatAt User

<@user|user>

FormatUser User Text

<@user|user did this and that>

FormatLink Text Text

FormatString Text

user did this & that