module Database.Groundhog.Expression
( Expression(..)
, Unifiable
, ExpressionOf
, (=.)
, (&&.), (||.)
, (==.), (/=.), (<.), (<=.), (>.), (>=.)
) where
import Database.Groundhog.Core
import Database.Groundhog.Instances ()
class Expression db r a where
toExpr :: a -> UntypedExpr db r
class (Expression db r a, Unifiable a a') => ExpressionOf db r a a'
instance (Expression db r a, Unifiable a a') => ExpressionOf db r a a'
instance PurePersistField a => Expression db r a where
toExpr = ExprPure
instance (PersistField a, db' ~ db, r' ~ r) => Expression db' r' (Expr db r a) where
toExpr = ExprRaw
instance (PersistEntity v, Constructor c, PersistField a, RestrictionHolder v c ~ r') => Expression db r' (Field v c a) where
toExpr = ExprField . fieldChain
instance (PersistEntity v, Constructor c, PersistField a, RestrictionHolder v c ~ r') => Expression db r' (SubField v c a) where
toExpr = ExprField . fieldChain
instance (PersistEntity v, Constructor c, RestrictionHolder v c ~ r') => Expression db r' (AutoKeyField v c) where
toExpr = ExprField . fieldChain
instance (PersistEntity v, IsUniqueKey k, k ~ Key v (Unique u), RestrictionHolder v (UniqueConstr k) ~ r')
=> Expression db r' (u (UniqueMarker v)) where
toExpr = ExprField . fieldChain
class Unifiable a b
instance Unifiable a a
instance (Normalize bk a (ak, r), Normalize ak b (bk, r)) => Unifiable a b
class Normalize counterpart t r | t -> r
instance (ExtractValue t (isPlain, r), NormalizeValue counterpart isPlain r r') => Normalize counterpart t r'
class ExtractValue t r | t -> r
instance r ~ (HFalse, a) => ExtractValue (Field v c a) r
instance r ~ (HFalse, a) => ExtractValue (SubField v c a) r
instance r ~ (HFalse, a) => ExtractValue (Expr db r' a) r
instance r ~ (HFalse, Key v BackendSpecific) => ExtractValue (AutoKeyField v c) r
instance r ~ (HFalse, Key v (Unique u)) => ExtractValue (u (UniqueMarker v)) r
instance r ~ (HTrue, a) => ExtractValue a r
class NormalizeValue counterpart isPlain t r | t isPlain -> r
instance NormalizeValue' t (isPlain, r) => NormalizeValue HFalse HFalse t (HFalse, r)
instance NormalizeValue' t (isPlain, r) => NormalizeValue HFalse HTrue t (isPlain, r)
instance r ~ (isPlain, t) => NormalizeValue HTrue isPlain t r
class NormalizeValue' t r | t -> r
instance (TypeEq (DefaultKey a) (Key a u) isDef,
r ~ (Not isDef, Maybe (NormalizeKey isDef (Key a u))))
=> NormalizeValue' (Maybe (Key a u)) r
instance (TypeEq (DefaultKey a) (Key a u) isDef,
r ~ (Not isDef, NormalizeKey isDef (Key a u)))
=> NormalizeValue' (Key a u) r
instance r ~ (HTrue, a) => NormalizeValue' a r
class TypeEq x y b | x y -> b
instance (b ~ HFalse) => TypeEq x y b
instance TypeEq x x HTrue
type family NormalizeKey isDef key
type instance NormalizeKey HTrue (Key a u) = a
type instance NormalizeKey HFalse a = a
type family Not bool
type instance Not HTrue = HFalse
type instance Not HFalse = HTrue
infixr 3 =.
(=.) ::
( FieldLike f db r a'
, Expression db r b
, Unifiable f b)
=> f -> b -> Update db r
f =. b = Update f (toExpr b)
(&&.) :: Cond db r -> Cond db r -> Cond db r
(||.) :: Cond db r -> Cond db r -> Cond db r
infixr 3 &&.
a &&. b = And a b
infixr 2 ||.
a ||. b = Or a b
(==.), (/=.) ::
( Expression db r a
, Expression db r b
, Unifiable a b)
=> a -> b -> Cond db r
(<.), (<=.), (>.), (>=.) ::
( Expression db r a
, Expression db r b
, Unifiable a b)
=> a -> b -> Cond db r
infix 4 ==., <., <=., >., >=.
a ==. b = Compare Eq (toExpr a) (toExpr b)
a /=. b = Compare Ne (toExpr a) (toExpr b)
a <. b = Compare Lt (toExpr a) (toExpr b)
a <=. b = Compare Le (toExpr a) (toExpr b)
a >. b = Compare Gt (toExpr a) (toExpr b)
a >=. b = Compare Ge (toExpr a) (toExpr b)