module System.Console.GetOpt.Generics.Result where
import Prelude ()
import Prelude.Compat
import Data.List
import System.Exit
import System.IO
data Result a
= Success a
| Errors [String]
| OutputAndExit String
deriving (Show, Eq, Ord, Functor)
instance Applicative Result where
pure = Success
OutputAndExit message <*> _ = OutputAndExit message
_ <*> OutputAndExit message = OutputAndExit message
Success f <*> Success x = Success (f x)
Errors a <*> Errors b = Errors (a ++ b)
Errors errs <*> Success _ = Errors errs
Success _ <*> Errors errs = Errors errs
instance Monad Result where
return = pure
Success a >>= b = b a
Errors errs >>= _ = Errors errs
OutputAndExit message >>= _ = OutputAndExit message
(>>) = (*>)
handleResult :: Result a -> IO a
handleResult result = case result of
Success a -> return a
OutputAndExit message -> do
putStr message
exitWith ExitSuccess
Errors errs -> do
mapM_ (hPutStr stderr . addNewlineIfMissing) errs
exitWith $ ExitFailure 1
addNewlineIfMissing :: String -> String
addNewlineIfMissing s
| "\n" `isSuffixOf` s = s
| otherwise = s ++ "\n"