A journey into Haskell web development

FirstSpock.hs

{-# LANGUAGE OverloadedStrings #-}

-- Ignore all the redundant string conversions
-- There's probably a better way to do it

import Control.Applicative
import qualified Data.Text as Text
import Data.ByteString.Lazy.Char8 (unpack)

import Web.Spock.Safe
import Data.Aeson

-- Router
main = do
  runSpock 3000 $ spockT id $ do
     -- Writes hello when visiting /
     get root $
       text "hello"

     -- Squares `n` in /square/n
     get ("square" <//> var) $ \number ->
       let intValue = read number in
       text $ Text.pack $ show (intValue ^ 2)

     -- Returns the JSON instance of a user with /user/name/password
     get ("user" <//> var <//> var) $ \username password ->
       let user = User username password in
       text $ Text.pack $ unpack $ encode user



data User = User { username :: Text.Text
                 , password :: Text.Text
                 } deriving (Show, Read, Eq)

-- JSON conversions

instance ToJSON User where
 toJSON (User username password) =
   object [ "username" .= username
          , "password" .= password
          ]

instance FromJSON User where
 parseJSON (Object v) =
   User <$> v .: "username"
        <*> v .: "password"