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rel8/src/Rel8/Expr/Order.hs
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1{-# language DataKinds #-}
3{-# options_ghc -fno-warn-redundant-constraints #-}
5module Rel8.Expr.Order
6 ( asc
7 , desc
8 , nullsFirst
9 , nullsLast
10 )
11where
13-- base
14import Data.Bifunctor ( first )
15import Prelude
17-- opaleye
18import Opaleye.Internal.HaskellDB.PrimQuery ( OrderOp( orderDirection, orderNulls ) )
19import qualified Opaleye.Internal.HaskellDB.PrimQuery as Opaleye
20import qualified Opaleye.Internal.Order as Opaleye
22-- rel8
23import Rel8.Expr ( Expr )
24import Rel8.Expr.Null ( unsafeUnnullify )
25import Rel8.Expr.Opaleye ( toPrimExpr )
26import Rel8.Order ( Order( Order ) )
27import Rel8.Type.Ord ( DBOrd )
30asc :: DBOrd a => Order (Expr a)
31asc = Order $ Opaleye.Order (\expr -> [(orderOp, toPrimExpr expr)])
32 where
33 orderOp :: Opaleye.OrderOp
34 orderOp = Opaleye.OrderOp
35 { orderDirection = Opaleye.OpAsc
36 , orderNulls = Opaleye.NullsLast
37 }
40desc :: DBOrd a => Order (Expr a)
41desc = Order $ Opaleye.Order (\expr -> [(orderOp, toPrimExpr expr)])
42 where
43 orderOp :: Opaleye.OrderOp
44 orderOp = Opaleye.OrderOp
45 { orderDirection = Opaleye.OpDesc
46 , orderNulls = Opaleye.NullsFirst
47 }
50nullsFirst :: Order (Expr a) -> Order (Expr (Maybe a))
51nullsFirst (Order (Opaleye.Order f)) =
52 Order $ Opaleye.Order $ fmap (first g) . f . unsafeUnnullify
53 where
54 g :: Opaleye.OrderOp -> Opaleye.OrderOp
55 g orderOp = orderOp { Opaleye.orderNulls = Opaleye.NullsFirst }
58nullsLast :: Order (Expr a) -> Order (Expr (Maybe a))
59nullsLast (Order (Opaleye.Order f)) =
60 Order $ Opaleye.Order $ fmap (first g) . f . unsafeUnnullify
61 where
62 g :: Opaleye.OrderOp -> Opaleye.OrderOp
63 g orderOp = orderOp { Opaleye.orderNulls = Opaleye.NullsLast }