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{-# LANGUAGE UndecidableInstances #-}

module Feldspar.Core.Constructs.MutableReference
where

import Data.IORef

import Language.Syntactic
import Language.Syntactic.Interpretation.Semantics
import Language.Syntactic.Constructs.Binding

import Feldspar.Lattice
import Feldspar.Core.Types
import Feldspar.Core.Interpretation

data MutableReference a
  where
    NewRef :: Type a => MutableReference (a :-> Full (Mut (IORef a)))
    GetRef :: Type a => MutableReference (IORef a :-> Full (Mut a))
    SetRef :: Type a => MutableReference (IORef a :-> a :-> Full (Mut ()))

instance WitnessCons MutableReference
  where
    witnessCons NewRef = ConsWit
    witnessCons GetRef = ConsWit
    witnessCons SetRef = ConsWit

instance MaybeWitnessSat ctx MutableReference
  where
    maybeWitnessSat _ _ = Nothing

instance Semantic MutableReference
  where
    semantics NewRef = Sem "newRef" newIORef
    semantics GetRef = Sem "getRef" readIORef
    semantics SetRef = Sem "setRef" writeIORef

instance ExprEq   MutableReference where exprEq = exprEqSem; exprHash = exprHashSem
instance Render   MutableReference where renderPart = renderPartSem
instance ToTree   MutableReference
instance Eval     MutableReference where evaluate = evaluateSem
instance EvalBind MutableReference where evalBindSym = evalBindSymDefault
instance Sharable MutableReference
  -- Will not be shared anyway, because 'maybeWitnessSat' returns 'Nothing'

instance AlphaEq dom dom dom env =>
    AlphaEq MutableReference MutableReference dom env
  where
    alphaEqSym = alphaEqSymDefault

instance SizeProp MutableReference
  where
    sizeProp NewRef _ = universal
    sizeProp GetRef _ = universal
    sizeProp SetRef _ = universal

instance (MutableReference :<: dom, Optimize dom dom) =>
    Optimize MutableReference dom
  where
    constructFeatUnOpt NewRef args = constructFeatUnOptDefaultTyp (MutType $ RefType typeRep) NewRef args
    constructFeatUnOpt GetRef args = constructFeatUnOptDefaultTyp (MutType typeRep) GetRef args
    constructFeatUnOpt SetRef args = constructFeatUnOptDefaultTyp (MutType typeRep) SetRef args