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{-# LANGUAGE GADTs #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Imperative.FromCore.Par where

import Language.Syntactic
import Language.Syntactic.Constructs.Monad
import Language.Syntactic.Constructs.Binding
import Language.Syntactic.Constructs.Binding.HigherOrder

import Feldspar.Core.Types
import Feldspar.Core.Interpretation
import Feldspar.Core.Constructs.Binding
import Feldspar.Core.Constructs.Par

import Feldspar.Compiler.Imperative.Frontend hiding (Type,Variable)
import Feldspar.Compiler.Imperative.FromCore.Interpretation
import Feldspar.Compiler.Imperative.Plugin.CollectFreeVars
import qualified Feldspar.Compiler.Imperative.Frontend as Front
import qualified Feldspar.Compiler.Imperative.Representation as AIR
import Feldspar.Transformation (transform, Result(..))

import Data.Map (elems)

instance ( Compile dom dom
         , Project (CLambda Type) dom
         , Project ParFeature dom
         )
      => Compile (MONAD Par) dom
  where
    compileProgSym Bind _ loc (ma :* (lam :$ body) :* Nil)
        | Just (SubConstr2 (Lambda v)) <- prjLambda lam
        , Just ParNew                  <- prj ma
        = do
            let info = getInfo ma
            let var = mkVar (compileTypeRep (infoType info) (infoSize info)) v
            declare var
            tellProg [iVarInit var]
            compileProg loc body

    compileProgSym Bind _ loc (ma :* (lam :$ body) :* Nil)
        | Just (SubConstr2 (Lambda v)) <- prjLambda lam
        = do
            e <- compileExpr ma
            withAlias v e $ compileProg loc body

    compileProgSym Then _ loc (ma :* mb :* Nil) = do
        compileExpr ma
        compileProg loc mb

    compileProgSym Return info loc (a :* Nil)
        | ParType UnitType <- infoType info = return ()
        | otherwise                         = compileProg loc a

    compileProgSym When _ loc (c :* action :* Nil) = do
        c' <- compileExpr c
        (_, Bl ds body) <- confiscateBlock $ compileProg loc action
        tellProg [If c' (Block ds body) Skip]

instance ( Compile dom dom
         , Project (Variable :|| Type) dom
         )
      => Compile ParFeature dom
  where
    compileExprSym = compileProgFresh

    compileProgSym ParRun _ loc (p :* Nil) = compileProg loc p

    compileProgSym ParGet _ loc (r :* Nil) = do
        iv <- compileExpr r
        tellProg [iVarGet loc iv]

    compileProgSym ParPut _ _ (r :* a :* Nil) = do
            iv  <- compileExpr r
            val <- compileExpr a
            i   <- freshId
            let var = Var (AIR.typeof val) $ "msg" ++ show i
            declare var
            assign var val
            tellProg [iVarPut iv var]

    compileProgSym ParFork _ loc (p :* Nil) = do
        -- Task core:
        (_, Bl ds t)  <- confiscateBlock $ compileProg loc p
        let b = Block ds t
        let vs = elems $ up $ transform Collect () () $ Front.fromInterface b
        funId  <- freshId
        let coreName = "task_core" ++ show funId
        tellDef [ProcDf coreName vs [] b]
        -- Task:
        let taskName = "task" ++ show funId
        let runTask = run coreName vs
        tellDef [ProcDf taskName [] [Front.Variable Void "params"] runTask]
        -- Spawn:
        tellProg [spawn taskName vs]

    compileProgSym ParYield _ _ Nil = return ()

    compileProgSym ParNew _ _ Nil = return ()