@@ -5,12 +5,14 @@
55{-# LANGUAGE MultiParamTypeClasses #-}
66{-# LANGUAGE TypeFamilies #-}
77{-# LANGUAGE TypeOperators #-}
8+{-# LANGUAGE UndecidableInstances #-}
89module Servant.Client.Generic
910 ( ClientLike(..)
10− , genericMkClient
11+ , genericMkClientL
12+ , genericMkClientP
1113 ) where
1214
13−import Generics.SOP (Generic, I(..), NP(..), NS(Z), Rep, SOP(..), to)
15+import Generics.SOP (Code, Generic, I(..), NP(..), NS(Z), Rep, SOP(..), to)
1416import Servant.API ((:<|>)(..))
1517import Servant.Client (ClientM)
1618
@@ -40,20 +42,20 @@ import Servant.Client (ClientM)
4042-- > instance (Client API ~ client) => ClientLike client APIClient
4143-- >
4244-- > data NestedClient = NestedClient
43−-- > { getString :: ClientM String
45+-- > { getString :: ClientM String
4446-- > , postBaz :: Maybe Char -> ClientM ()
4547-- > } deriving GHC.Generic
4648-- >
47−-- > instance Generic.SOP.Generic
49+-- > instance Generic.SOP.Generic NestedClient
4850-- > instance (Client NestedAPI ~ client) => ClientLike client NestedClient
4951-- >
5052-- > mkAPIClient :: APIClient
5153-- > mkAPIClient = mkClient (client (Proxy :: Proxy API))
5254class ClientLike client custom where
5355 mkClient :: client -> custom
54− default mkClient :: (Generic custom, GClientLikeP client xs, SOP I '[xs] ~ Rep custom)
56+ default mkClient :: (Generic custom, Code custom ~ '[xs], GClientList client '[], GClientLikeL (ClientList client '[]) xs)
5557 => client -> custom
56− mkClient = genericMkClient
58+ mkClient = genericMkClientL
5759
5860instance ClientLike client custom
5961 => ClientLike (a -> client) (a -> custom) where
@@ -62,9 +64,7 @@ instance ClientLike client custom
6264instance ClientLike (ClientM a) (ClientM a) where
6365 mkClient = id
6466
65−-- | This class is used to match client functions to the
66−-- representation of client structure type as sum of products
67−-- and basically does all the internal job to build this structure.
67+-- GClientLikeP
6868class GClientLikeP client xs where
6969 gMkClientP :: client -> NP I xs
7070
@@ -75,8 +75,37 @@ instance (GClientLikeP b (y ': xs), ClientLike a x)
7575instance ClientLike a x => GClientLikeP a '[x] where
7676 gMkClientP a = I (mkClient a) :* Nil
7777
78+-- GClientLikeL
79+class GClientLikeL (xs :: [*]) (ys :: [*]) where
80+ gMkClientL :: NP I xs -> NP I ys
81+
82+instance GClientLikeL '[] '[] where
83+ gMkClientL Nil = Nil
84+
85+instance (ClientLike x y, GClientLikeL xs ys) => GClientLikeL (x ': xs) (y ': ys) where
86+ gMkClientL (I x :* xs) = I (mkClient x) :* gMkClientL xs
87+
88+type family ClientList (client :: *) (acc :: [*]) :: [*] where
89+ ClientList (a :<|> b) acc = ClientList a (ClientList b acc)
90+ ClientList a acc = a ': acc
91+
92+class GClientList client (acc :: [*]) where
93+ gClientList :: client -> NP I acc -> NP I (ClientList client acc)
94+
95+instance (GClientList b acc, GClientList a (ClientList b acc))
96+ => GClientList (a :<|> b) acc where
97+ gClientList (a :<|> b) acc = gClientList a (gClientList b acc)
98+
99+instance {-# OVERLAPPABLE #-} (ClientList client acc ~ (client ': acc))
100+ => GClientList client acc where
101+ gClientList c acc = I c :* acc
102+
78103-- | Generate client structure from client type.
79−genericMkClient :: (Generic custom, GClientLikeP client xs, SOP I '[xs] ~ Rep custom)
104+genericMkClientL :: (Generic custom, Code custom ~ '[xs], GClientList client '[], GClientLikeL (ClientList client '[]) xs)
105+ => client -> custom
106+genericMkClientL = to . SOP . Z . gMkClientL . flip gClientList Nil
107+
108+genericMkClientP :: (Generic custom, Code custom ~ '[xs], GClientLikeP client xs)
80109 => client -> custom
81−genericMkClient = to . SOP . Z . gMkClientP
110+genericMkClientP = to . SOP . Z . gMkClientP
82111