module Opaleye.Internal.Join where
import qualified Opaleye.Internal.Tag as T
import qualified Opaleye.Internal.PackMap as PM
import Opaleye.Internal.Column (Column, Nullable)
import qualified Opaleye.Column as C
import Data.Profunctor (Profunctor, dimap)
import Data.Profunctor.Product (ProductProfunctor, empty, (***!))
import qualified Data.Profunctor.Product.Default as D
import qualified Opaleye.Internal.HaskellDB.PrimQuery as HPQ
newtype NullMaker a b = NullMaker (a -> b)
toNullable :: NullMaker a b -> a -> b
toNullable (NullMaker f) = f
extractLeftJoinFields :: Int -> T.Tag -> HPQ.PrimExpr
-> PM.PM [(HPQ.Symbol, HPQ.PrimExpr)] HPQ.PrimExpr
extractLeftJoinFields n = PM.extractAttr ("result" ++ show n ++ "_")
instance D.Default NullMaker (Column a) (Column (Nullable a)) where
def = NullMaker C.unsafeCoerceColumn
instance D.Default NullMaker (Column (Nullable a)) (Column (Nullable a)) where
def = NullMaker C.unsafeCoerceColumn
instance Profunctor NullMaker where
dimap f g (NullMaker h) = NullMaker (dimap f g h)
instance ProductProfunctor NullMaker where
empty = NullMaker empty
NullMaker f ***! NullMaker f' = NullMaker (f ***! f')