Delete cruft, add Reader monad to some internal ai

src/Sound.hs

@@ -50,10 +50,7 @@ In the update:
  -}
 playAndUpdate :: Ord a => SoundData a -> M.Map a Sound -> IO (M.Map a Sound)
 playAndUpdate sData newSounds 
-    = updateSounds (_loadedChunks sData) (mergeSounds newSounds (_playingSounds sData))
-
-mergeSounds :: Ord a => M.Map a Sound -> M.Map a Sound -> M.Map a Sound
-mergeSounds as bs = M.unionWith mergeSound as bs
+    = updateSounds (_loadedChunks sData) (M.unionWith mergeSound newSounds (_playingSounds sData))
 
 mergeSound :: Sound -> Sound -> Sound
 mergeSound newS oldS 
@@ -85,7 +82,7 @@ tryPlay sd s = do
         Mix.halt i
         Mix.playOn i Mix.Once (sd IM.! _soundChunkID s)
     return $ s 
-        & soundChannel  .~ Just i
+        & soundChannel  ?~ i
         & soundStatus   .~ Playing
 
 repetitions :: Sound -> Mix.Times
@@ -100,14 +97,13 @@ tryGetChannel s = case _soundChannel s of
 
 decrementTimer :: Sound -> IO Sound
 decrementTimer s = case _soundTime s of
-    Just t | t > 0     -> return $ s & soundTime .~ Just (t - 1)
-           | otherwise -> fadeOutMaybe (_soundChannel s) (_soundFadeTime s)
+    Just t 
+        | t > 0     -> return $ s & soundTime ?~ t - 1
+        | otherwise -> fadeOutMaybe (_soundChannel s) (_soundFadeTime s)
                             >> return (s & soundTime .~ Nothing
                                          & soundStatus .~ FadingOut)
     Nothing -> return s
 
---applyPosition = return
-
 applyPosition :: Sound -> IO Sound
 applyPosition s = case _soundPos s of
     Nothing     -> return s