gistfile1.hs

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Data.ByteString.Lazy.Char8 (pack)
import Web.Scotty as S
import Network.Wai.Middleware.RequestLogger
import Data.Aeson
import Data.Aeson.Types
import Control.Lens hiding ((.=), (??))
import Data.Aeson.Lens
import qualified Data.Text as T
import Control.Error
import Control.Applicative
import qualified Data.HashMap.Strict as H
import Network.HTTP.Types

data TypeOne = TypeOne T.Text TypeTwo TypeThree
  deriving (Show)

data TypeTwo = TypeTwo Double
  deriving (Show)

data TypeThree = TypeThree Double
  deriving (Show)

main :: IO ()
main = scotty 3000 $ do
  middleware logStdoutDev

  post "/pdor" $ do
    api_key <- param "api_key"
    input   <- param "input"

    typeOne <- runEitherT $ do
      result       <- (decode (pack input) :: Maybe Value) ?? "Could not parse. Input JSON document is malformed"
      typeTwoObj   <- (result ^? key "typeTwo")            ?? "Could not find key typeTwo in JSON document."
      typeThreeObj <- (result ^? key "typeThree")          ?? "Could not find key typeThree in JSON document."
      name         <- (result ^? key "name" . _String)     ?? "Could not find key name in JSON document."
      typeTwo      <- hoistEither $ prependLeft "Error when parsing TypeTwo: " $ parseEither jsonTypeTwo typeTwoObj
      typeThree    <- hoistEither $ prependLeft "Error when parsing TypeThree: " $ parseEither jsonTypeThree typeThreeObj

      return $ TypeOne name typeTwo typeThree

    case typeOne of
      Left errorMsg -> do
        _ <- status badRequest400
        S.json $ object ["error" .= errorMsg]
      Right _ ->
        -- do something with the parsed Haskell type
        S.json $ object ["api_key" .= (api_key :: String), "message" .= ("success" :: String)]

prependLeft :: String -> Either String a -> Either String a
prependLeft msg (Left s) = Left (msg ++ s)
prependLeft _ x = x

jsonTypeTwo :: Value -> Parser TypeTwo
jsonTypeTwo (Object v) = TypeTwo <$> v .: "val"
jsonTypeTwo _ = fail $ "no data present for TypeTwo"

jsonTypeThree :: Value -> Parser TypeThree
jsonTypeThree (Object v) = TypeThree <$> v .: "val"
jsonTypeThree _ = fail $ "no data present for TypeThree"