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{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Feldspar.Compiler.Backend.C.Plugin.VariableRoleAssigner where

import Feldspar.Transformation

data VariableRoleAssigner = VariableRoleAssigner

data Parameters = Parameters
    { inParametersVRA  :: [String]
    , outParametersVRA :: [String]
    }

instance Transformation VariableRoleAssigner where
    type From VariableRoleAssigner = ()
    type To VariableRoleAssigner = ()
    type Down VariableRoleAssigner = Parameters
    type Up VariableRoleAssigner = ()
    type State VariableRoleAssigner = ()

instance Transformable VariableRoleAssigner Variable where
        transform _ _ d v = Result v' () () where
            v' = v { varRole = if (varName v `elem` outParametersVRA d) ||
                            (isComposite v && (varName v `elem` inParametersVRA d))
                        then Pointer else Value
                   , varLabel = ()
                   }

instance Transformable VariableRoleAssigner Entity where
        transform t s _ p@(ProcDef _ i o _ _ _) = defaultTransform t s d' p where
            d' = Parameters
                    { inParametersVRA = map varName i
                    , outParametersVRA = map varName o
                    }
        transform t s d p = defaultTransform t s d p

instance Plugin VariableRoleAssigner where
    type ExternalInfo VariableRoleAssigner = ()
    executePlugin self@VariableRoleAssigner _ procedure = 
        result $ transform self ({-state-}) (Parameters [] []) procedure

isComposite :: Variable () -> Bool
isComposite v = case varType v of
    ArrayType{}  -> True
    StructType{} -> True
    _            -> False