module Mail.Hailgun.Errors
    ( HailgunErrorResponse(..) -- TODO Make it so that herMessage is a hidden detail in the next version
    , toHailgunError
    , serverError
    , unexpectedError
    , gatherErrors
    , mapError
    ) where

import           Control.Applicative
import           Control.Monad       (mzero)
import           Data.Aeson
import qualified Data.Text           as T

-- TODO make this Hailgun specific and different for the Mailgun api. That way there is the correct
-- separation of concerns.
-- | An error that comes from Mailgun or the Hailgun API.
data HailgunErrorResponse = HailgunErrorResponse
   { herMessage :: String -- ^ A generic message describing the error.
   }

toHailgunError :: String -> HailgunErrorResponse
toHailgunError = HailgunErrorResponse

instance FromJSON HailgunErrorResponse where
   parseJSON (Object v) = HailgunErrorResponse
      <$> v .: T.pack "message"
   parseJSON _ = mzero

serverError :: Either HailgunErrorResponse a
serverError = retError "Server Errors - something is wrong on Mailgun’s end"

unexpectedError :: Int -> Either HailgunErrorResponse a
unexpectedError x = retError $ "Unexpected Non-Standard Mailgun Error: " ++ show x

retError :: String -> Either HailgunErrorResponse a
retError = Left . toHailgunError

mapError :: Either String a -> Either HailgunErrorResponse a
mapError = either retError Right

gatherErrors :: Either HailgunErrorResponse HailgunErrorResponse -> Either HailgunErrorResponse a
gatherErrors = either Left Left