module Graphics.Text.Font.Choose.Result (Result(..), resultFromPointer) where

import Foreign.Storable (peek)
import Foreign.Ptr (Ptr, ptrNull)
import Control.Exception (throwIO, throw, Exception)

data Result = Match | NoMatch | TypeMismatch | ResultNoId | OutOfMemory
    deriving (Eq, Show, Read, Enum)

resultFromPointer :: Ptr Int -> IO Result
resultFromPointer res = toEnum <$> peek res

data Error = ErrTypeMismatch | ErrResultNoId | ErrOutOfMemory deriving (Eq, Show, Read)
instance Exception Error

throwResult :: Result -> IO a -> IO (Maybe a)
throwResult Match x = Just <$> x
throwResult NoMatch _ = return Nothing
throwResult TypeMismatch = throwIO ErrTypeMismatch
throwResult ResultNoId = throwIO ErrResultNoId
throwResult OutOfMemory = throwIO ErrOutOfMemory

throwInt :: Int -> IO a -> IO (Maybe a)
throwInt = throwResult . toEnum
throwPtr :: Ptr Int -> IO a -> IO (Maybe a)
throwPtr a b = resultFromPointer a >>= flip throwResult b

throwFalse :: Bool -> IO ()
throwFalse True = return ()
throwFalse False = throwIO ErrOutOfMemory
throwFalse' :: IO Bool -> IO ()
throwFalse' = (>>= throwFalse)

throwNull :: Ptr a -> Ptr a
throwNull ptr | ptr == ptrNull = throw ErrOutOfMemory
    | otherwise = ptr