fresco-binding-0.1.0: Fresco/Component.hs

--
--  Fresco Framework for Multi-Language Programming
--  Copyright 2015-2016 Peter Althainz
--    
--  Distributed under the Apache License, Version 2.0
--  (See attached file LICENSE or copy at 
--  http:--www.apache.org/licenses/LICENSE-2.0)
-- 
--  file: haskell/Fresco/Component.hs
--
    
{-# LANGUAGE TypeSynonymInstances #-}

-- | Components of the Entity Component System of Fresco binding
module Fresco.Component
(
    ComponentType (..),
    Component,
    ComponentClass (..)
)
where

import Data.Word
import Data.MessagePack
import Data.ByteString
import Data.Text
import Data.Text.Encoding

-- | Components in Entities are indexed by ComponentType
data ComponentType a = ComponentType Word64 deriving (Eq, Show, Ord)

-- | Components are stored as ByteString
type Component = ByteString

-- | ComponentClass is the typeclass of data types, which can be components
class ComponentClass a where
  toObj :: a -> Object
  fromObj :: Object -> a

instance ComponentClass () where
   toObj () = ObjectNil
   fromObj ObjectNil = ()

instance ComponentClass Text where
   toObj text = ObjectString (encodeUtf8 text)
   fromObj (ObjectString bs) = decodeUtf8 bs 

instance ComponentClass (ComponentType a) where
   toObj (ComponentType i) = ObjectInt (fromIntegral i)
   fromObj (ObjectInt i) = ComponentType (fromIntegral i)
   
instance ComponentClass Bool where
    toObj b = ObjectBool b
    fromObj (ObjectBool b) = b
    
instance ComponentClass Int where
    toObj i = ObjectInt (fromIntegral i)
    fromObj (ObjectInt i) = fromIntegral i
    
instance ComponentClass a => ComponentClass (Maybe a) where
    toObj Nothing = ObjectArray [ObjectInt 0]
    toObj (Just v) = ObjectArray [ObjectInt 1, toObj v]
    fromObj (ObjectArray [ObjectInt 0]) = Nothing
    fromObj (ObjectArray [ObjectInt 1, v_o]) = Just (fromObj v_o)