module Hackage.Security.Util.Exit where

import MyPrelude
import Control.Monad (liftM)
import Control.Monad.Except (ExceptT, runExceptT, throwError)

{-------------------------------------------------------------------------------
  Auxiliary: multiple exit points
-------------------------------------------------------------------------------}

-- | Multiple exit points
--
-- We can simulate the imperative code
--
-- > if (cond1)
-- >   return exp1;
-- > if (cond2)
-- >   return exp2;
-- > if (cond3)
-- >   return exp3;
-- > return exp4;
--
-- as
--
-- > multipleExitPoints $ do
-- >   when (cond1) $
-- >     exit exp1
-- >   when (cond2) $
-- >     exit exp2
-- >   when (cond3) $
-- >     exit exp3
-- >   return exp4
multipleExitPoints :: Monad m => ExceptT a m a -> m a
multipleExitPoints :: forall (m :: * -> *) a. Monad m => ExceptT a m a -> m a
multipleExitPoints = forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM forall a. Either a a -> a
aux forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall e (m :: * -> *) a. ExceptT e m a -> m (Either e a)
runExceptT
  where
    aux :: Either a a -> a
    aux :: forall a. Either a a -> a
aux (Left  a
a) = a
a
    aux (Right a
a) = a
a

-- | Function exit point (see 'multipleExitPoints')
exit :: Monad m => e -> ExceptT e m a
exit :: forall (m :: * -> *) e a. Monad m => e -> ExceptT e m a
exit = forall e (m :: * -> *) a. MonadError e m => e -> m a
throwError