-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Ref
-- Copyright   :  (c) 2020-2021 EMQ Technologies Co., Ltd.
-- License     :  BSD-style (see the LICENSE file)
--
-- Maintainer  :  Feng Lee, feng@emqx.io
--                Yang M, yangm@emqx.io
-- Stability   :  experimental
-- Portability :  portable
--
-- The Erlang Reference datatype.
--
-----------------------------------------------------------------------------
module Data.Ref where

import Control.Monad (IO)
import Data.Eq (class Eq)
import Data.Ord
  ( class Ord
  , Ordering(..)
  )
import Data.Show (class Show)

-- | An alias for erlang `Reference`
type Ref = Reference

-- |
-- Erlang reference is a term that is unique in an Erlang runtime system,
-- created by calling `make_ref`.
--
foreign import data Reference :: Type

foreign import makeRef :: IO Reference

instance Eq Reference where
  eq = eqRefImpl

instance Ord Reference where
  compare = cmpRefImpl LT EQ GT

instance Show Reference where
  show = showRefImpl

foreign import eqRefImpl
  :: Reference -> Reference -> Boolean

foreign import cmpRefImpl
  :: Ordering
  -> Ordering
  -> Ordering
  -> Reference
  -> Reference
  -> Ordering

foreign import showRefImpl :: Reference -> String