--------------------------------------------------------------------
-- |
-- Module    : Data.Ruby.Marshal
-- Copyright : (c) Philip Cunningham, 2015
-- License   : MIT
--
-- Maintainer:  hello@filib.io
-- Stability :  experimental
-- Portability: portable
--
-- Simple interface to parse Ruby Marshal binary.
--
--------------------------------------------------------------------

module Data.Ruby.Marshal (
  -- * Decoding
    decode
  , decodeEither
  -- * Lifting into and lowering from RubyObject
  , fromRuby
  , toRuby
  -- * Re-exported modules
  , module Data.Ruby.Marshal.Types
) where

import           Control.Monad.State.Strict   (evalStateT)
import qualified Data.ByteString              as BS
import           Data.Ruby.Marshal.Get
import           Data.Ruby.Marshal.Monad      (emptyCache, runMarshal)
import           Data.Ruby.Marshal.RubyObject
import           Data.Ruby.Marshal.Types
import           Data.Serialize               (runGet)

-- | Parses a subset of Ruby objects serialised with Marshal, Ruby's
-- built-in binary serialisation format.
decode :: BS.ByteString
       -- ^ Serialised Ruby object
       -> Maybe RubyObject
       -- ^ De-serialisation result
decode :: ByteString -> Maybe RubyObject
decode = Either String RubyObject -> Maybe RubyObject
forall a b. Either a b -> Maybe b
hush (Either String RubyObject -> Maybe RubyObject)
-> (ByteString -> Either String RubyObject)
-> ByteString
-> Maybe RubyObject
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ByteString -> Either String RubyObject
decodeEither

-- | Parses a subset of Ruby objects serialised with Marshal, Ruby's
-- built-in binary serialisation format.
decodeEither :: BS.ByteString
             -- ^ Serialised Ruby object
             -> Either String RubyObject
             -- ^ Error message or de-serialisation result
decodeEither :: ByteString -> Either String RubyObject
decodeEither = Get RubyObject -> ByteString -> Either String RubyObject
forall a. Get a -> ByteString -> Either String a
runGet (StateT Cache Get RubyObject -> Cache -> Get RubyObject
forall (m :: * -> *) s a. Monad m => StateT s m a -> s -> m a
evalStateT (Marshal RubyObject -> StateT Cache Get RubyObject
forall a. Marshal a -> StateT Cache Get a
runMarshal Marshal RubyObject
getRubyObject) Cache
emptyCache)

-- | Converts an Either to a Maybe.
hush :: Either a b -> Maybe b
hush :: Either a b -> Maybe b
hush = (a -> Maybe b) -> (b -> Maybe b) -> Either a b -> Maybe b
forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either (Maybe b -> a -> Maybe b
forall a b. a -> b -> a
const Maybe b
forall a. Maybe a
Nothing) b -> Maybe b
forall a. a -> Maybe a
Just