Simple url redirector in 30 lines

gistfile1.hs

{-# LANGUAGE TypeFamilies, QuasiQuotes, MultiParamTypeClasses, TemplateHaskell, OverloadedStrings #-}
import Yesod
import Yesod.Handler
import qualified Data.Text as T
import qualified Data.Map as M
import System.IO

type ShurlsMap = M.Map T.Text String

myMap :: ShurlsMap
myMap = M.insert (T.pack "g") "https://google.com/ncr" M.empty 

data HsRedir = HsRedir

mkYesod "HsRedir" [parseRoutes|
/#T.Text RedirR GET
|]

instance Yesod HsRedir

-- Handlers

getRedirR :: T.Text -> Handler RepHtml
getRedirR text = do 
    case M.lookup text myMap of
        Just url -> redirect url
        Nothing -> notFound

main :: IO ()
main = warpDebug 3000 HsRedir