bson-generic-0.0.5: src/Data/Bson/Generic.hs
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
------------------------------------------------------------------------------
-- | Examples
--
-- > data Test0 = A | B | C deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Test0
-- > instance FromBSON Test0
-- >
-- > (fromBSON $ toBSON A) :: Maybe Test0
--
--
-- > data Test1 = Test1 String String deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Test1
-- > instance FromBSON Test1
-- >
-- > (fromBSON $ toBSON $ Test1 "aa" "bb") :: Maybe Test1
--
--
-- > data Test2 = Test2 { test20 :: String, test21 :: String } deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Test2
-- > instance FromBSON Test2
-- >
-- > (fromBSON $ toBSON $ Test2 "aa" "bb") :: Maybe Test2
--
--
-- > data Test3 = Test3 { test30 :: Test2, test31 :: String } deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Test3
-- > instance FromBSON Test3
-- >
-- > (fromBSON $ toBSON $ Test3 (Test2 "aa" "bb") "cc") :: Maybe Test3
--
--
-- > data Test4 = Test4 { test4Key :: ObjectKey, test4 :: String } deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Test4
-- > instance FromBSON Test4
-- >
-- > (fromBSON $ toBSON $ Test4 (ObjectKey . Just $ unsafePerformIO genObjectId) "something") :: Maybe Test4
-- > (fromBSON $ toBSON $ Test4 (ObjectKey Nothing) "something") :: Maybe Test4
--
--
-- > data Comment = Comment { author :: String, comments :: [Comment] } deriving (Generic, Typeable, Show, Eq)
-- > instance ToBSON Comment
-- > instance FromBSON Comment
-- >
-- > (fromBSON $ toBSON $ Comment "Joe1" [Comment "Joe2" [], Comment "Joe3" [Comment "Joe4" [], Comment "Joe5" []]]) :: Maybe Comment
--
--
-- Representation
--
-- > toBSON $ Test2 "aa" "bb"
-- >
-- > [ test20: "aa", test21: "bb" ]
--
-- > toBSON $ Test3 (Test2 "aa" "bb") "cc"
-- >
-- > [ test30: [ test20: "aa", test21: "bb"], test31: "cc" ]
--
-- > toBSON $ Test4 (ObjectKey . Just $ unsafePerformIO genObjectId) "something"
-- >
-- > [ _id: 4f226c27900faa06ab000001, test4: "something" ]
--
-- > toBSON $ Test4 (ObjectKey Nothing) "something"
-- >
-- > [ test4: "something" ]
--
-- > toBSON $ Comment "Joe1" [ Comment "Joe2" []
-- > , Comment "Joe3" [ Comment "Joe4" []
-- > , Comment "Joe5" []
-- > ]
-- > ]
-- >
-- > [ author: "Joe1", comments: [ [ author: "Joe2", comments: []]
-- > , [ author: "Joe3", comments: [ [ author: "Joe4", comments: []]
-- > , [ author: "Joe5", comments: []]
-- > ]]
-- > ]]
module Data.Bson.Generic
( ToBSON(..)
, FromBSON(..)
, ObjectKey(..)
, keyLabel
, constructorLabel
) where
import GHC.Generics
import qualified Data.Bson as BSON (lookup)
import Data.Bson
import Data.UString (u)
import Data.Typeable
import Control.Monad
keyLabel :: Label
keyLabel = u "_id"
constructorLabel :: Label
constructorLabel = u "_co"
class GConstructorCount f where
gconstructorCount :: f a -> Int
instance GConstructorCount V1 where
gconstructorCount _ = 0
instance (GConstructorCount a) => GConstructorCount (D1 d a) where
gconstructorCount (M1 x) = gconstructorCount x
instance (Constructor c) => GConstructorCount (C1 c a) where
gconstructorCount c = 1
instance (GConstructorCount a, GConstructorCount b) => GConstructorCount (a :+: b) where
gconstructorCount (_ :: (a :+: b) r) = gconstructorCount (undefined :: a r) +
gconstructorCount (undefined :: b r)
constructorCount :: (Generic a, GConstructorCount (Rep a)) => a -> Int
constructorCount x = gconstructorCount $ from x
------------------------------------------------------------------------------
newtype ObjectKey = ObjectKey { unObjectKey :: Maybe ObjectId } deriving (Generic, Typeable, Show, Eq)
instance FromBSON ObjectKey
instance ToBSON ObjectKey
------------------------------------------------------------------------------
instance (FromBSON a, ToBSON a, Typeable a, Show a, Eq a) => Val a where
val x = Doc $ toBSON x
cast' (Doc x) = fromBSON x
cast' _ = Nothing
------------------------------------------------------------------------------
class ToBSON a where
toBSON :: a -> Document
default toBSON :: (Generic a, GConstructorCount (Rep a), GToBSON (Rep a)) => a -> Document
toBSON a = genericToBSON (constructorCount a) (from a)
class GToBSON f where
genericToBSON :: Int -> f a -> Document
-- | Unit type -> Empty document
instance GToBSON U1 where
genericToBSON _ U1 = []
-- | Sum of types
instance (GToBSON a, GToBSON b) => GToBSON (a :*: b) where
genericToBSON n (x :*: y) = genericToBSON n x ++ genericToBSON n y
-- | Product of types
instance (GToBSON a, GToBSON b) => GToBSON (a :+: b) where
genericToBSON n (L1 x) = genericToBSON n x
genericToBSON n (R1 x) = genericToBSON n x
-- | Datatype information tag
instance (GToBSON a) => GToBSON (D1 c a) where
genericToBSON n (M1 x) = genericToBSON n x
-- | Constructor tag
instance (GToBSON a, Constructor c) => GToBSON (C1 c a) where
genericToBSON 0 (M1 x) = genericToBSON 0 x
genericToBSON 1 (M1 x) = genericToBSON 1 x
genericToBSON n c@(M1 x) = genericToBSON n x ++ [ constructorLabel =: conName c ]
-- | Selector tag
instance (Val a, Selector s) => GToBSON (S1 s (K1 i a)) where
genericToBSON _ s@(M1 (K1 x)) = [u (selName s) =: x]
-- | ObjectKey special treatment
instance (Selector s) => GToBSON (S1 s (K1 i ObjectKey)) where
genericToBSON _ (M1 (K1 (ObjectKey (Just key)))) = [ keyLabel =: key ]
genericToBSON _ _ = []
-- | Constants
instance (ToBSON a) => GToBSON (K1 i a) where
genericToBSON _ (K1 x) = toBSON x
------------------------------------------------------------------------------
------------------------------------------------------------------------------
class FromBSON a where
fromBSON :: Document -> Maybe a
default fromBSON :: (Generic a, GConstructorCount (Rep a), GFromBSON (Rep a)) => Document -> Maybe a
fromBSON doc = maybe Nothing (Just . to) (genericFromBSON (constructorCount (undefined :: a)) doc)
class GFromBSON f where
genericFromBSON :: Int -> Document -> Maybe (f a)
instance GFromBSON U1 where
genericFromBSON _ doc = Just U1
instance (GFromBSON a, GFromBSON b) => GFromBSON (a :*: b) where
genericFromBSON n doc = do
x <- (genericFromBSON n doc)
y <- (genericFromBSON n doc)
return (x :*: y)
instance (GFromBSON a, GFromBSON b) => GFromBSON (a :+: b) where
genericFromBSON n doc = left `mplus` right
where left = maybe Nothing (Just . L1) (genericFromBSON n doc)
right = maybe Nothing (Just . R1) (genericFromBSON n doc)
instance (GFromBSON a, Constructor c) => GFromBSON (C1 c a) where
genericFromBSON 0 doc = maybe Nothing (Just . M1) (genericFromBSON 0 doc)
genericFromBSON 1 doc = maybe Nothing (Just . M1) (genericFromBSON 0 doc)
genericFromBSON n doc = do
cname <- BSON.lookup constructorLabel doc
if (cname == (conName (undefined :: M1 C c a r)))
then maybe Nothing (Just . M1) (genericFromBSON n doc)
else Nothing
instance (GFromBSON a) => GFromBSON (M1 D c a) where
genericFromBSON n doc = genericFromBSON n doc >>= return . M1
instance (Val a, Selector s) => GFromBSON (S1 s (K1 i a)) where
genericFromBSON n doc = (BSON.lookup sname doc) >>= return . M1 . K1
where sname = u . selName $ (undefined :: S1 s (K1 i a) r)
-- | ObjectKey special treatment
instance (Selector s) => GFromBSON (S1 s (K1 i ObjectKey)) where
genericFromBSON n doc = Just . M1 . K1 $ ObjectKey (BSON.lookup keyLabel doc)
------------------------------------------------------------------------------