module Rakka.Utils
    ( yesOrNo
    , parseYesOrNo
    , maybeA
    , deleteIfEmpty
    , chomp
    )
    where

import           Control.Arrow
import           Control.Arrow.ArrowList


yesOrNo :: Bool -> String
yesOrNo True  = "yes"
yesOrNo False = "no"


parseYesOrNo :: ArrowChoice a => a String Bool
parseYesOrNo 
    = proc str -> do case str of
                       "yes" -> returnA -< True
                       "no"  -> returnA -< False
                       _     -> returnA -< error ("Expected yes or no: " ++ str)


maybeA :: (ArrowList a, ArrowChoice a) => a b c -> a b (Maybe c)
maybeA a = listA a
           >>>
           proc xs -> case xs of
                        []    -> returnA -< Nothing
                        (x:_) -> returnA -< Just x


deleteIfEmpty :: (ArrowList a, ArrowChoice a) => a String String
deleteIfEmpty
    = proc str -> do case str of
                       "" -> none    -< ()
                       _  -> returnA -< str


chomp :: String -> String
chomp = reverse . snd . break (/= '\n') . reverse