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{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -fno-warn-orphans -fno-warn-missing-fields #-}
-- | This module provides utilities for creating backends. Regular users do not
-- need to use this module.
module Database.Persist.TH
( -- * Parse entity defs
persistWith
, persistUpperCase
, persistLowerCase
, persistFileWith
-- ** Deprecated synonyms
, persist
, persistFile
-- * Turn @EntityDef@s into types
, mkPersist
, MkPersistSettings (..)
, sqlSettings
-- * Various other TH functions
, mkMigrate
, mkSave
, mkDeleteCascade
, share
, derivePersistField
, persistFieldFromEntity
-- ** Deprecated
, share2
) where
import Prelude hiding ((++), take, concat, splitAt)
import Database.Persist.EntityDef
import Database.Persist.Quasi
import Database.Persist.Store
import Database.Persist.Query.Internal
import Database.Persist.GenericSql (Migration, SqlPersist, migrate)
import Database.Persist.Util (nullable)
import Database.Persist.TH.Library (apE)
import Language.Haskell.TH.Quote
import Language.Haskell.TH.Syntax
import Data.Char (toLower, toUpper)
import Control.Monad (forM, (<=<), mzero)
import Control.Monad.Trans.Control (MonadBaseControl)
import Control.Monad.IO.Class (MonadIO)
import qualified System.IO as SIO
import Data.Text (pack, Text, append, unpack, concat, uncons, cons)
import qualified Data.Text.IO as TIO
import Data.List (foldl')
import Data.Monoid (mappend, mconcat)
import qualified Data.Map as M
import Data.Aeson
( ToJSON (toJSON), FromJSON (parseJSON), (.=), object
, Value (Object), (.:), (.:?)
)
import Control.Applicative (pure, (<*>))
-- | Converts a quasi-quoted syntax into a list of entity definitions, to be
-- used as input to the template haskell generation code (mkPersist).
persistWith :: PersistSettings -> QuasiQuoter
persistWith ps = QuasiQuoter
{ quoteExp = lift . parse ps . pack
}
-- | Deprecate synonym for 'persistUpperCase'.
persist :: QuasiQuoter
persist = persistUpperCase
{-# DEPRECATED persist "Please use persistUpperCase instead." #-}
-- | Apply 'persistWith' to 'upperCaseSettings'.
persistUpperCase :: QuasiQuoter
persistUpperCase = persistWith upperCaseSettings
-- | Apply 'persistWith' to 'lowerCaseSettings'.
persistLowerCase :: QuasiQuoter
persistLowerCase = persistWith lowerCaseSettings
-- | Same as 'persistWith', but uses an external file instead of a
-- quasiquotation.
persistFileWith :: PersistSettings -> FilePath -> Q Exp
persistFileWith ps fp = do
#ifdef GHC_7_4
qAddDependentFile fp
#endif
h <- qRunIO $ SIO.openFile fp SIO.ReadMode
qRunIO $ SIO.hSetEncoding h SIO.utf8_bom
s <- qRunIO $ TIO.hGetContents h
lift $ parse ps s
-- | Deprecated function. Equivalent to @persistFileWith upperCaseSettings@.
persistFile :: FilePath -> Q Exp
persistFile = persistFileWith upperCaseSettings
-- | Create data types and appropriate 'PersistEntity' instances for the given
-- 'EntityDef's. Works well with the persist quasi-quoter.
mkPersist :: MkPersistSettings -> [EntityDef] -> Q [Dec]
mkPersist mps ents = do
x <- fmap mconcat $ mapM persistFieldFromEntity ents
y <- fmap mconcat $ mapM (mkEntity mps) ents
z <- fmap mconcat $ mapM mkJSON ents
return $ mconcat [x, y, z]
-- | Settings to be passed to the 'mkPersist' function.
data MkPersistSettings = MkPersistSettings
{ mpsBackend :: Type
-- ^ Which database backend we\'re using.
--
-- When generating data types, each type is given a generic version- which
-- works with any backend- and a type synonym for the commonly used
-- backend. This is where you specify that commonly used backend.
}
-- | Use the 'SqlPersist' backend.
sqlSettings :: MkPersistSettings
sqlSettings = MkPersistSettings
{ mpsBackend = ConT ''SqlPersist
}
recName :: Text -> Text -> Text
recName dt f = lowerFirst dt ++ upperFirst f
lowerFirst :: Text -> Text
lowerFirst t =
case uncons t of
Just (a, b) -> cons (toLower a) b
Nothing -> t
upperFirst :: Text -> Text
upperFirst t =
case uncons t of
Just (a, b) -> cons (toUpper a) b
Nothing -> t
dataTypeDec :: EntityDef -> Dec
dataTypeDec t =
DataD [] nameG [KindedTV backend monadTransKind] [RecC name cols]
$ map (mkName . unpack) $ entityDerives t
where
monadKind = StarK `ArrowK` StarK
monadTransKind = monadKind `ArrowK` monadKind
mkCol x (FieldDef n _ ty as) =
(mkName $ unpack $ recName x $ unHaskellName n,
NotStrict,
pairToType backend (ty, nullable as)
)
nameG = mkName $ unpack $ unHaskellName (entityHaskell t) ++ suffix
name = mkName $ unpack $ unHaskellName $ entityHaskell t
cols = map (mkCol $ unHaskellName $ entityHaskell t) $ entityFields t
backend = mkName "backend"
readMay :: Read a => String -> Maybe a
readMay s =
case reads s of
(x, _):_ -> Just x
[] -> Nothing
entityUpdates :: EntityDef -> [(HaskellName, FieldType, Bool, PersistUpdate)]
entityUpdates =
concatMap go . entityFields
where
go (FieldDef x _ y as) = map (\a -> (x, y, nullable as, a)) [minBound..maxBound]
uniqueTypeDec :: EntityDef -> Dec
uniqueTypeDec t =
DataInstD [] ''Unique
[ ConT (mkName $ unpack (unHaskellName (entityHaskell t) ++ suffix))
`AppT` VarT backend, VarT backend2
]
(map (mkUnique backend t) $ entityUniques t)
[]
where
backend = mkName "backend"
backend2 = mkName "backend2"
mkUnique :: Name -> EntityDef -> UniqueDef -> Con
mkUnique backend t (UniqueDef (HaskellName constr) _ fields) =
NormalC (mkName $ unpack constr) types
where
types = map (go . flip lookup3 (entityFields t))
$ map (unHaskellName . fst) fields
go :: (FieldType, Bool) -> (Strict, Type)
go (_, True) = error "Error: cannot have nullables in unique"
go (ft, y) = (NotStrict, pairToType backend (ft, y))
lookup3 :: Text -> [FieldDef] -> (FieldType, Bool)
lookup3 s [] =
error $ unpack $ "Column not found: " ++ s ++ " in unique " ++ constr
lookup3 x ((FieldDef (HaskellName x') _ y z):rest)
| x == x' = (y, nullable z)
| otherwise = lookup3 x rest
pairToType :: Name -- ^ backend
-> (FieldType, Bool) -- ^ True == has Maybe attr
-> Type
pairToType backend (s, False) = idType backend s
pairToType backend (s, True) = ConT (mkName "Maybe") `AppT` idType backend s
idType :: Name -> FieldType -> Type
idType backend typ =
case stripId typ of
Just typ' ->
ConT ''Key
`AppT` VarT backend
`AppT` (ConT (mkName $ unpack $ typ' ++ "Generic") `AppT` VarT backend)
Nothing -> ftToType typ
degen :: [Clause] -> [Clause]
degen [] =
let err = VarE (mkName "error") `AppE` LitE (StringL
"Degenerate case, should never happen")
in [Clause [WildP] (NormalB err) []]
degen x = x
mkToPersistFields :: [(String, Int)] -> Q Dec
mkToPersistFields pairs = do
clauses <- mapM go pairs
return $ FunD (mkName "toPersistFields") $ degen clauses
where
go :: (String, Int) -> Q Clause
go (constr, fields) = do
xs <- sequence $ replicate fields $ newName "x"
let pat = ConP (mkName constr) $ map VarP xs
sp <- [|SomePersistField|]
let bod = ListE $ map (AppE sp . VarE) xs
return $ Clause [pat] (NormalB bod) []
mkToFieldNames :: [UniqueDef] -> Q Dec
mkToFieldNames pairs = do
pairs' <- mapM go pairs
return $ FunD (mkName "persistUniqueToFieldNames") $ degen pairs'
where
go (UniqueDef constr _ names) = do
names' <- lift names
return $
Clause
[RecP (mkName $ unpack $ unHaskellName constr) []]
(NormalB names')
[]
mkToUpdate :: String -> [(String, PersistUpdate)] -> Q Dec
mkToUpdate name pairs = do
pairs' <- mapM go pairs
return $ FunD (mkName name) $ degen pairs'
where
go (constr, pu) = do
pu' <- lift pu
return $ Clause [RecP (mkName constr) []] (NormalB pu') []
mkUniqueToValues :: [UniqueDef] -> Q Dec
mkUniqueToValues pairs = do
pairs' <- mapM go pairs
return $ FunD (mkName "persistUniqueToValues") $ degen pairs'
where
go :: UniqueDef -> Q Clause
go (UniqueDef constr _ names) = do
xs <- mapM (const $ newName "x") names
let pat = ConP (mkName $ unpack $ unHaskellName constr) $ map VarP xs
tpv <- [|toPersistValue|]
let bod = ListE $ map (AppE tpv . VarE) xs
return $ Clause [pat] (NormalB bod) []
mkToFieldName :: String -> [(String, String)] -> Dec
mkToFieldName func pairs =
FunD (mkName func) $ degen $ map go pairs
where
go (constr, name) =
Clause [RecP (mkName constr) []] (NormalB $ LitE $ StringL name) []
mkToOrder :: [(String, Exp)] -> Dec
mkToOrder pairs =
FunD (mkName "persistOrderToOrder") $ degen $ map go pairs
where
go (constr, val) =
Clause [RecP (mkName constr) []] (NormalB val) []
mkToValue :: String -> [String] -> Dec
mkToValue func = FunD (mkName func) . degen . map go
where
go constr =
let x = mkName "x"
in Clause [ConP (mkName constr) [VarP x]]
(NormalB $ VarE (mkName "toPersistValue") `AppE` VarE x)
[]
mkHalfDefined :: String -> Int -> Dec
mkHalfDefined constr count' =
FunD (mkName "halfDefined")
[Clause [] (NormalB
$ foldl AppE (ConE $ mkName constr)
(replicate count' $ VarE $ mkName "undefined")) []]
mkFromPersistValues :: EntityDef -> Q [Clause]
mkFromPersistValues t = do
nothing <- [|Left $(liftT "Invalid fromPersistValues input")|]
let cons' = ConE $ mkName $ unpack $ unHaskellName $ entityHaskell t
xs <- mapM (const $ newName "x") $ entityFields t
fs <- [|fromPersistValue|]
let xs' = map (AppE fs . VarE) xs
let pat = ListP $ map VarP xs
ap' <- [|apE|]
just <- [|Right|]
let cons'' = just `AppE` cons'
return
[ Clause [pat] (NormalB $ foldl (go ap') cons'' xs') []
, Clause [WildP] (NormalB nothing) []
]
where
go ap' x y = InfixE (Just x) ap' (Just y)
mkEntity :: MkPersistSettings -> EntityDef -> Q [Dec]
mkEntity mps t = do
t' <- lift t
let nameT = unHaskellName $ entityHaskell t
let nameS = unpack nameT
let clazz = ConT ''PersistEntity `AppT` (ConT (mkName $ unpack $ unHaskellName (entityHaskell t) ++ suffix) `AppT` VarT (mkName "backend"))
tpf <- mkToPersistFields [(nameS, length $ entityFields t)]
fpv <- mkFromPersistValues t
utv <- mkUniqueToValues $ entityUniques t
puk <- mkUniqueKeys t
fields <- mapM (mkField t) $ FieldDef
(HaskellName "Id")
(entityID t)
(FTTypeCon Nothing $ unHaskellName (entityHaskell t) ++ "Id")
[]
: entityFields t
toFieldNames <- mkToFieldNames $ entityUniques t
return
[ dataTypeDec t
, TySynD (mkName nameS) [] $
ConT (mkName $ unpack $ nameT ++ suffix)
`AppT` mpsBackend mps
, TySynD (mkName $ unpack $ unHaskellName (entityHaskell t) ++ "Id") [] $
ConT ''Key `AppT` mpsBackend mps `AppT` ConT (mkName nameS)
, InstanceD [] clazz $
[ uniqueTypeDec t
, FunD (mkName "entityDef") [Clause [WildP] (NormalB t') []]
, tpf
, FunD (mkName "fromPersistValues") fpv
, mkHalfDefined nameS $ length $ entityFields t
, toFieldNames
, utv
, puk
, DataInstD
[]
''EntityField
[ ConT (mkName $ unpack $ nameT ++ suffix) `AppT` VarT (mkName "backend")
, VarT $ mkName "typ"
]
(map fst fields)
[]
, FunD (mkName "persistFieldDef") (map snd fields)
, TySynInstD
(mkName "PersistEntityBackend")
[ConT (mkName $ unpack $ unHaskellName (entityHaskell t) ++ suffix) `AppT` VarT (mkName "backend")]
(VarT (mkName "backend"))
, FunD (mkName "persistIdField") [Clause [] (NormalB $ ConE $ mkName $ unpack $ unHaskellName (entityHaskell t) ++ "Id") []]
]
]
-- | produce code similar to the following:
--
-- instance PersistEntity e => PersistField e where
-- toPersistValue = PersistMap $ zip columNames (map toPersistValue . toPersistFields)
-- fromPersistValue (PersistMap o) = fromPersistValues $ map (\(_,v) ->
-- casefromPersistValue v of
-- Left e -> error e
-- Right r -> r) o
-- fromPersistValue x = Left $ "Expected PersistMap, received: " ++ show x
-- sqlType _ = SqlString
persistFieldFromEntity :: EntityDef -> Q [Dec]
persistFieldFromEntity e = do
ss <- [|SqlString|]
let columnNames = map (unpack . unHaskellName . fieldHaskell) (entityFields e)
obj <- [|\ent -> PersistMap $ zip (map pack columnNames) (map toPersistValue $ toPersistFields ent)|]
fpv <- [|\x -> fromPersistValues $ map (\(_,v) -> case fromPersistValue v of
Left e' -> error $ unpack e'
Right r -> r) x|]
let typ = ConT (mkName $ entityName `mappend` "Generic")
`AppT` VarT (mkName "backend")
compose <- [|(<=<)|]
getPersistMap' <- [|getPersistMap|]
return
[ persistFieldInstanceD typ
[ sqlTypeFunD ss
, FunD (mkName "toPersistValue") [ Clause [] (NormalB obj) [] ]
, FunD (mkName "fromPersistValue")
[ Clause [] (NormalB $ InfixE (Just fpv) compose $ Just getPersistMap') []
]
]
]
where
entityName = (unpack $ unHaskellName $ entityHaskell e)
updateConName :: Text -> Text -> PersistUpdate -> Text
updateConName name s pu = concat
[ name
, upperFirst s
, case pu of
Assign -> ""
_ -> pack $ show pu
]
-- | Apply the given list of functions to the same @EntityDef@s.
--
-- This function is useful for cases such as:
--
-- >>> share [mkSave "myDefs", mkPersist sqlSettings] [persistLowerCase|...|]
share :: [[EntityDef] -> Q [Dec]] -> [EntityDef] -> Q [Dec]
share fs x = fmap mconcat $ mapM ($ x) fs
-- | Deprecated, restricted version of 'share'.
share2 :: ([EntityDef] -> Q [Dec])
-> ([EntityDef] -> Q [Dec])
-> [EntityDef]
-> Q [Dec]
share2 f g x = do
y <- f x
z <- g x
return $ y `mappend` z
{-# DEPRECATED share2 "Use share instead" #-}
-- | Save the @EntityDef@s passed in under the given name.
mkSave :: String -> [EntityDef] -> Q [Dec]
mkSave name' defs' = do
let name = mkName name'
defs <- lift defs'
return [ SigD name $ ListT `AppT` ConT ''EntityDef
, FunD name [Clause [] (NormalB defs) []]
]
data Dep = Dep
{ depTarget :: Text
, depSourceTable :: HaskellName
, depSourceField :: HaskellName
, depSourceNull :: Bool
}
-- | Generate a 'DeleteCascade' instance for the given @EntityDef@s.
mkDeleteCascade :: [EntityDef] -> Q [Dec]
mkDeleteCascade defs = do
let deps = concatMap getDeps defs
mapM (go deps) defs
where
getDeps :: EntityDef -> [Dep]
getDeps def =
concatMap getDeps' $ entityFields def
where
getDeps' :: FieldDef -> [Dep]
getDeps' (FieldDef name _ ftyp attribs) =
let isNull = nullable attribs
in case stripId ftyp of
Just f ->
return Dep
{ depTarget = f
, depSourceTable = entityHaskell def
, depSourceField = name
, depSourceNull = isNull
}
Nothing -> []
go :: [Dep] -> EntityDef -> Q Dec
go allDeps EntityDef{entityHaskell = name} = do
let deps = filter (\x -> depTarget x == unHaskellName name) allDeps
key <- newName "key"
del <- [|delete|]
dcw <- [|deleteCascadeWhere|]
just <- [|Just|]
filt <- [|Filter|]
eq <- [|Eq|]
left <- [|Left|]
let mkStmt :: Dep -> Stmt
mkStmt dep = NoBindS
$ dcw `AppE`
ListE
[ filt `AppE` ConE (mkName $ unpack filtName)
`AppE` (left `AppE` val (depSourceNull dep))
`AppE` eq
]
where
filtName = unHaskellName (depSourceTable dep) ++
upperFirst (unHaskellName $ depSourceField dep)
val False = VarE key
val True = just `AppE` VarE key
let stmts :: [Stmt]
stmts = map mkStmt deps `mappend`
[NoBindS $ del `AppE` VarE key]
return $
InstanceD
[ ClassP ''PersistQuery [VarT $ mkName "backend", VarT $ mkName "m"]
, ClassP ''Monad [VarT $ mkName "m"]
]
(ConT ''DeleteCascade `AppT`
(ConT (mkName $ unpack $ unHaskellName name ++ suffix) `AppT` VarT (mkName "backend"))
`AppT` VarT (mkName "backend")
`AppT` VarT (mkName "m")
)
[ FunD (mkName "deleteCascade")
[Clause [VarP key] (NormalB $ DoE stmts) []]
]
mkUniqueKeys :: EntityDef -> Q Dec
mkUniqueKeys def = do
c <- clause
return $ FunD (mkName "persistUniqueKeys") [c]
where
clause = do
xs <- forM (entityFields def) $ \(FieldDef x _ _ _) -> do
x' <- newName $ '_' : unpack (unHaskellName x)
return (x, x')
let pcs = map (go xs) $ entityUniques def
let pat = ConP
(mkName $ unpack $ unHaskellName $ entityHaskell def)
(map (VarP . snd) xs)
return $ Clause [pat] (NormalB $ ListE pcs) []
go :: [(HaskellName, Name)] -> UniqueDef -> Exp
go xs (UniqueDef name _ cols) =
foldl' (go' xs) (ConE (mkName $ unpack $ unHaskellName name)) (map fst cols)
go' :: [(HaskellName, Name)] -> Exp -> HaskellName -> Exp
go' xs front col =
let Just col' = lookup col xs
in front `AppE` VarE col'
sqlTypeFunD :: Exp -> Dec
sqlTypeFunD st = FunD (mkName "sqlType")
[ Clause [WildP] (NormalB st) [] ]
persistFieldInstanceD :: Type -> [Dec] -> Dec
persistFieldInstanceD typ =
InstanceD [] (ConT ''PersistField `AppT` typ)
-- | Automatically creates a valid 'PersistField' instance for any datatype
-- that has valid 'Show' and 'Read' instances. Can be very convenient for
-- 'Enum' types.
derivePersistField :: String -> Q [Dec]
derivePersistField s = do
ss <- [|SqlString|]
tpv <- [|PersistText . pack . show|]
fpv <- [|\dt v ->
case fromPersistValue v of
Left e -> Left e
Right s' ->
case reads $ unpack s' of
(x, _):_ -> Right x
[] -> Left $ "Invalid " ++ dt ++ ": " ++ s'|]
return
[ persistFieldInstanceD (ConT $ mkName s)
[ sqlTypeFunD ss
, FunD (mkName "toPersistValue")
[ Clause [] (NormalB tpv) []
]
, FunD (mkName "fromPersistValue")
[ Clause [] (NormalB $ fpv `AppE` LitE (StringL s)) []
]
]
]
-- | Creates a single function to perform all migrations for the entities
-- defined here. One thing to be aware of is dependencies: if you have entities
-- with foreign references, make sure to place those definitions after the
-- entities they reference.
mkMigrate :: String -> [EntityDef] -> Q [Dec]
mkMigrate fun allDefs = do
body' <- body
return
[ SigD (mkName fun) typ
, FunD (mkName fun) [Clause [] (NormalB body') []]
]
where
defs = filter isMigrated allDefs
isMigrated def = not $ "no-migrate" `elem` entityAttrs def
typ = ForallT [PlainTV $ mkName "m"]
[ ClassP ''MonadBaseControl [ConT ''IO, VarT $ mkName "m"]
, ClassP ''MonadIO [VarT $ mkName "m"]
]
$ ConT ''Migration `AppT` (ConT ''SqlPersist `AppT` VarT (mkName "m"))
body :: Q Exp
body =
case defs of
[] -> [|return ()|]
_ -> do
defsName <- newName "defs"
defsStmt <- do
u <- [|undefined|]
e <- [|entityDef|]
let defsExp = ListE $ map (AppE e . undefinedEntityTH u) defs
return $ LetS [ValD (VarP defsName) (NormalB defsExp) []]
stmts <- mapM (toStmt $ VarE defsName) defs
return (DoE $ defsStmt : stmts)
toStmt :: Exp -> EntityDef -> Q Stmt
toStmt defsExp ed = do
u <- [|undefined|]
m <- [|migrate|]
return $ NoBindS $ m `AppE` defsExp `AppE` (undefinedEntityTH u ed)
undefinedEntityTH :: Exp -> EntityDef -> Exp
undefinedEntityTH u = SigE u . ConT . mkName . unpack . unHaskellName . entityHaskell
instance Lift EntityDef where
lift (EntityDef a b c d e f g h) =
[|EntityDef
$(lift a)
$(lift b)
$(lift c)
$(liftTs d)
$(lift e)
$(lift f)
$(liftTs g)
$(liftMap h)
|]
instance Lift FieldDef where
lift (FieldDef a b c d) = [|FieldDef $(lift a) $(lift b) $(lift c) $(liftTs d)|]
instance Lift UniqueDef where
lift (UniqueDef a b c) = [|UniqueDef $(lift a) $(lift b) $(lift c)|]
pack' :: String -> Text
pack' = pack
#if !MIN_VERSION_text(0, 11, 2)
{-# NOINLINE pack' #-}
#endif
liftT :: Text -> Q Exp
liftT t = [|pack' $(lift (unpack t))|]
liftTs :: [Text] -> Q Exp
liftTs = fmap ListE . mapM liftT
liftTss :: [[Text]] -> Q Exp
liftTss = fmap ListE . mapM liftTs
liftMap :: M.Map Text [[Text]] -> Q Exp
liftMap m = [|M.fromList $(fmap ListE $ mapM liftPair $ M.toList m)|]
liftPair :: (Text, [[Text]]) -> Q Exp
liftPair (t, ts) = [|($(liftT t), $(liftTss ts))|]
instance Lift HaskellName where
lift (HaskellName t) = [|HaskellName $(liftT t)|]
instance Lift DBName where
lift (DBName t) = [|DBName $(liftT t)|]
instance Lift FieldType where
lift (FTTypeCon Nothing t) = [|FTTypeCon Nothing $(liftT t)|]
lift (FTTypeCon (Just x) t) = [|FTTypeCon (Just $(liftT x)) $(liftT t)|]
lift (FTApp x y) = [|FTApp $(lift x) $(lift y)|]
lift (FTList x) = [|FTList $(lift x)|]
instance Lift PersistFilter where
lift Eq = [|Eq|]
lift Ne = [|Ne|]
lift Gt = [|Gt|]
lift Lt = [|Lt|]
lift Ge = [|Ge|]
lift Le = [|Le|]
lift In = [|In|]
lift NotIn = [|NotIn|]
lift (BackendSpecificFilter x) = [|BackendSpecificFilter $(liftT x)|]
instance Lift PersistUpdate where
lift Assign = [|Assign|]
lift Add = [|Add|]
lift Subtract = [|Subtract|]
lift Multiply = [|Multiply|]
lift Divide = [|Divide|]
-- Ent
-- fieldName FieldType
--
-- forall . typ ~ FieldType => EntFieldName
--
-- EntFieldName = FieldDef ....
mkField :: EntityDef -> FieldDef -> Q (Con, Clause)
mkField et cd = do
let con = ForallC
[]
[EqualP (VarT $ mkName "typ") maybeTyp]
$ NormalC name []
bod <- lift cd
let cla = Clause
[ConP name []]
(NormalB bod)
[]
return (con, cla)
where
name = mkName $ unpack $ concat
[ unHaskellName $ entityHaskell et
, upperFirst $ unHaskellName $ fieldHaskell cd
]
maybeTyp =
if nullable $ fieldAttrs cd
then ConT ''Maybe `AppT` typ
else typ
typ =
case stripId $ fieldType cd of
Just ft ->
ConT ''Key
`AppT` (VarT $ mkName "backend")
`AppT`
let con = ConT $ mkName $ unpack $ ft ++ suffix
in con `AppT` VarT (mkName "backend")
Nothing -> ftToType $ fieldType cd
ftToType :: FieldType -> Type
ftToType (FTTypeCon Nothing t) = ConT $ mkName $ unpack t
ftToType (FTTypeCon (Just m) t) = ConT $ mkName $ unpack $ concat [m, ".", t]
ftToType (FTApp x y) = ftToType x `AppT` ftToType y
ftToType (FTList x) = ListT `AppT` ftToType x
suffix :: Text
suffix = "Generic"
infixr 5 ++
(++) :: Text -> Text -> Text
(++) = append
mkJSON :: EntityDef -> Q [Dec]
mkJSON def | not ("json" `elem` entityAttrs def) = return []
mkJSON def = do
pureE <- [|pure|]
apE' <- [|(<*>)|]
packE <- [|pack|]
dotEqualE <- [|(.=)|]
dotColonE <- [|(.:)|]
dotColonQE <- [|(.:?)|]
objectE <- [|object|]
obj <- newName "obj"
mzeroE <- [|mzero|]
xs <- mapM (newName . unpack . unHaskellName . fieldHaskell)
$ entityFields def
let con = ConT $ mkName $ unpack
(unHaskellName (entityHaskell def) ++ "Generic")
conName = mkName $ unpack $ unHaskellName $ entityHaskell def
typ = con `AppT` VarT (mkName "backend")
toJSONI = InstanceD
[]
(ConT ''ToJSON `AppT` typ)
[toJSON']
toJSON' = FunD 'toJSON $ return $ Clause
[ConP conName $ map VarP xs]
(NormalB $ objectE `AppE` ListE pairs)
[]
pairs = zipWith toPair (entityFields def) xs
toPair f x = InfixE
(Just (packE `AppE` LitE (StringL $ unpack $ unHaskellName $ fieldHaskell f)))
dotEqualE
(Just $ VarE x)
fromJSONI = InstanceD
[]
(ConT ''FromJSON `AppT` typ)
[parseJSON']
parseJSON' = FunD 'parseJSON
[ Clause [ConP 'Object [VarP obj]]
(NormalB $ foldl'
(\x y -> InfixE (Just x) apE' (Just y))
(pureE `AppE` ConE conName)
pulls
)
[]
, Clause [WildP] (NormalB mzeroE) []
]
pulls = map toPull $ entityFields def
toPull f = InfixE
(Just $ VarE obj)
(if nullable (fieldAttrs f) then dotColonQE else dotColonE)
(Just $ AppE packE $ LitE $ StringL $ unpack $ unHaskellName $ fieldHaskell f)
return [toJSONI, fromJSONI]
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