Attribute.hs

{-
 *  Programmer:	Piotr Borek
 *  E-mail:     piotrborek@op.pl
 *  Copyright 2017 Piotr Borek
 *
 *  Distributed under the terms of the GPL (GNU Public License)
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}
{-# LANGUAGE BangPatterns #-}

module Simple.UI.Core.Attribute (
    Attribute,
    AttributeList,
    attributeNew,
--    attributeNewOverride,
    get,
    set,
    modify,
    add,
    add',
    readAttr,
    writeAttr,
    modifyAttr,
    connectAttrTo
) where

import           Control.Monad
import           Control.Monad.IO.Class
import           Data.IORef

newtype Attribute a = Attribute (IORef (a, [Attribute a]))

type AttributeList a = Attribute [a]

attributeNew :: MonadIO m => a -> m (Attribute a)
attributeNew !x = liftIO $ Attribute <$> newIORef (x, [])

get :: MonadIO m => s -> (s -> Attribute a) -> m a
get obj getAttr = readAttr $ getAttr obj

set :: MonadIO m => s -> (s -> Attribute a) -> a -> m ()
set obj getAttr = writeAttr $ getAttr obj

modify :: MonadIO m => s -> (s -> Attribute a) -> (a -> a) -> m ()
modify obj getAttr = modifyAttr $ getAttr obj

add :: MonadIO m => s -> (s -> AttributeList a) -> (b -> a) -> b -> m ()
add obj getAttr cast !x = modify obj getAttr $ \xs -> xs ++ [cast x]

add' :: MonadIO m => s -> (s -> AttributeList a) -> a -> m ()
add' obj getAttr !x = add obj getAttr id x

readAttr :: MonadIO m => Attribute a -> m a
readAttr (Attribute attr) = liftIO $ fst <$> readIORef attr

writeAttr :: MonadIO m => Attribute a -> a -> m ()
writeAttr (Attribute attr) !x = liftIO $ do
    (_ , z1) <- readIORef attr
    writeIORef attr (x, z1)
    forM_ z1 $ flip writeAttr x

modifyAttr :: MonadIO m => Attribute a -> (a -> a) -> m ()
modifyAttr attr f           = readAttr attr >>= \x -> writeAttr attr (f x)

connectAttrTo :: MonadIO m => Attribute a -> Attribute a -> m ()
connectAttrTo (Attribute from) to = liftIO $ modifyIORef' from $ \(x, z) -> (x, to:z)

{-
data Attribute a = Attribute { _get :: IO a, _set :: a -> IO () }

attributeNew :: MonadIO m => a -> m (Attribute a)
attributeNew !x = do
    ref <- liftIO $ newIORef x
    return Attribute {
        _get = liftIO $ readIORef ref,
        _set = liftIO . writeIORef ref
    }

attributeNewOverride :: IO a -> (a -> IO ()) -> Attribute a
attributeNewOverride getter setter =
    Attribute {
        _get = getter,
        _set = setter
    }

get :: MonadIO m => s -> (s -> Attribute a) -> m a
get obj getAttr = liftIO $ _get (getAttr obj)

set :: MonadIO m => s -> (s -> Attribute a) -> a -> m ()
set obj getAttr !x = liftIO $ _set (getAttr obj) x

modify :: MonadIO m => s -> (s -> Attribute a) -> (a -> a) -> m ()
modify obj getAttr f = liftIO $ do
    x <- _get (getAttr obj)
    _set (getAttr obj) (f x)
-}