Kadena Interview

gistfile1.hs

import Control.Monad
import Data.ByteString(ByteString)
import Control.Monad (ExceptT (..))
import Data.Kind

type Errors = [String]

data HeistConfig (m :: Type -> Type) = HeistConfig

newtype TemplateName = TemplateName String

data HeistState (n :: Type -> Type) = HeistState

data MIMEType

initHeist :: Monad n => HeistConfig n -> n (Either Errors (HeistState n))
initHeist = undefined

renderTemplate :: Monad n => HeistState n -> TemplateName -> Maybe (n Builder, MIMEType)
renderTemplate = undefined

toByteString :: Builder -> ByteString
toByteString = undefined

yourFunc1 :: HeistConfig IO -> TemplateName -> IO (Either Errors ByteString)
yourFunc1 hc nm = do
  eitherState <- initHeist hc
  case eitherState of
    Left errs -> pure $ Left errs
    Right heistState -> do
        case renderTemplate heistState nm  of
            Nothing -> pure $ Left
            Just (ioBuilder, _mt) -> Right . toByteString <$> ioBuilder

renderTemplateEither ::  Monad n => HeistState n -> TemplateName -> Either Errors (n Builder, MIMETYpe)
renderTemplateEither hs tn =  case renderTemplate hs tn of
    Nothing -> Left ["Can not rennder template"]
    Just  x -> Right x

yourFunc2 :: HeistConfig IO -> TemplateName -> IO (Either Errors ByteString)
yourFunc2 hc nm = runExceptT $ do
    hState <- ExceptT (initHeist hc) 
    (ioBuilder, _mt) <- ExceptT (pure $ renderTemplateEither state nm)
    ExceptT (Right . toByteString <$> ioBuilder)