Option.hs

{- This file is part of settings.
 -
 - Written in 2015 by fr33domlover <fr33domlover@rel4tion.org>.
 -
 - ♡ Copying is an act of love. Please copy, reuse and share.
 -
 - The author(s) have dedicated all copyright and related and neighboring
 - rights to this software to the public domain worldwide. This software is
 - distributed without any warranty.
 -
 - You should have received a copy of the CC0 Public Domain Dedication along
 - with this software. If not, see
 - <http://creativecommons.org/publicdomain/zero/1.0/>.
 -}

module Data.Settings.Option
    ( mkOptionV
    , mkOptionS
    )
where

import Control.Monad (liftM)
import Data.Bool (bool)
import Data.Settings.Types

mkOptionV :: (Monad m, OptionValue v)
          => m v
          -> (v -> m Bool)
          -> m ()
          -> Option m
mkOptionV get set reset = Option
    { optGet   = liftM (showOption) get
    , optSet   = \ s -> case readOption s of
        Nothing -> return $ Just $ InvalidValueForType s
        Just v  -> liftM (bool (Just $ InvalidValue s) Nothing) $ set v
    , optReset = reset
    }

mkOptionS :: (MonadSettings m s, OptionValue v)
          => (s -> v)
          -> (v -> s -> Maybe s)
          -> (s -> (Maybe v, s))
          -> (v -> m ()) -- callback
          -> Option m
mkOptionS get set reset cb =
    mkOptionV
        (liftM get getSettings)
        (\ v -> do
            s <- getSettings
            case set v s of
                Just s' -> putSettings s' >> cb v >> return True
                Nothing -> return False
        )
        ( do
            s <- getSettings
            let (mv, s') = reset s
            putSettings s'
            case mv of
                Just v  -> cb v
                Nothing -> return ()
        )