101 lines
3.2 KiB
Haskell
101 lines
3.2 KiB
Haskell
{-# LANGUAGE UndecidableInstances #-}
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module Database.Esqueleto.Utils.TH
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( SqlIn(..)
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, sqlInTuple, sqlInTuples
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, unValueN, unValueNIs
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, sqlIJproj, sqlLOJproj, sqlFOJproj
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) where
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import ClassyPrelude
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import qualified Database.Esqueleto as E
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import qualified Database.Esqueleto.Internal.Sql as E (SqlSelect)
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import Database.Persist (PersistField)
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import Language.Haskell.TH
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import Data.List (foldr1, foldl)
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import Utils.TH
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class E.SqlSelect a r => SqlIn a r | a -> r, r -> a where
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sqlIn :: a -> [r] -> E.SqlExpr (E.Value Bool)
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instance SqlEq a => SqlIn (E.SqlExpr (E.Value a)) (E.Value a) where
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sqlIn x = foldr (\x' e -> e E.||. sqlEq (E.val $ E.unValue x') x) (E.val False)
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class PersistField a => SqlEq a where
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sqlEq :: E.SqlExpr (E.Value a) -> E.SqlExpr (E.Value a) -> E.SqlExpr (E.Value Bool)
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instance {-# OVERLAPPABLE #-} PersistField a => SqlEq a where
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sqlEq = (E.==.)
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instance PersistField a => SqlEq (Maybe a) where
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sqlEq a b = (E.isNothing a E.&&. E.isNothing b) E.||. a E.==. b
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sqlInTuples :: [Int] -> DecsQ
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sqlInTuples = mapM sqlInTuple
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sqlInTuple :: Int -> DecQ
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sqlInTuple arity = do
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tyVars <- replicateM arity $ newName "t"
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vVs <- replicateM arity $ newName "v"
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xVs <- replicateM arity $ newName "x"
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xsV <- newName "xs"
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let
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matchE = lam1E (tupP $ map (\vV -> conP 'E.Value [varP vV]) vVs) (foldr1 (\e1 e2 -> [e|$(e1) E.&&. $(e2)|]) $ zipWith (\(varE -> vE) (varE -> xE) -> [e|E.val $(vE) `sqlEq` $(xE)|]) vVs xVs)
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tupTy f = foldl (\typ v -> typ `appT` f (varT v)) (tupleT arity) tyVars
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instanceD (cxt $ map (\v -> [t|SqlEq $(varT v)|]) tyVars) [t|SqlIn $(tupTy $ \v -> [t|E.SqlExpr (E.Value $(v))|]) $(tupTy $ \v -> [t|E.Value $(v)|])|]
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[ funD 'sqlIn
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[ clause [tupP $ map varP xVs, varP xsV]
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( guardedB
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[ normalGE [e|null $(varE xsV)|] [e|E.val False|]
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, normalGE [e|otherwise|] [e|foldr1 (E.||.) $ map $(matchE) $(varE xsV)|]
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]
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) []
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]
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]
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-- | Generic unValuing of Tuples of Values, i.e.
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--
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-- > $(unValueN 3) :: (E.Value a, E.Value b, E.Value c) -> (a,b,c)
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unValueN :: Int -> ExpQ
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unValueN arity = do
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vs <- replicateM arity $ newName "v"
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let pat = tupP $ map varP vs
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let uvE v = [e|E.unValue $(varE v)|]
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let rhs = tupE $ map uvE vs
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lam1E pat rhs
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-- | Generic unValuing of certain indices of a Tuple, i.e.
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--
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-- > $(unValueNIs 3 [1,3]) :: (E.Value a, b, E.Value c) -> (a,b,c)
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unValueNIs :: Int -> [Int] -> ExpQ
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unValueNIs arity uvIdx = do
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vs <- replicateM arity $ newName "v"
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let pat = tupP $ map varP vs
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let rhs = tupE $ zipWith (curry uvEi) vs [1 ..]
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lam1E pat rhs
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where
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uvEi (v,i) | i `elem` uvIdx = [e|E.unValue $(varE v)|]
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| otherwise = varE v
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-- | Generic projections for InnerJoin-tuples
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-- gives I-th element of N-tuple of left-associative InnerJoin-pairs, i.e.
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--
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-- > $(projN n m) :: (t1 `E.InnerJoin` .. `E.InnerJoin` tn) -> tm@ (for m<=n)
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sqlIJproj :: Int -> Int -> ExpQ
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sqlIJproj = leftAssociativePairProjection 'E.InnerJoin
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sqlLOJproj :: Int -> Int -> ExpQ
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sqlLOJproj = leftAssociativePairProjection 'E.LeftOuterJoin
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sqlFOJproj :: Int -> Int -> ExpQ
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sqlFOJproj = leftAssociativePairProjection 'E.FullOuterJoin
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