{-
Parser DSL for the \"aeson\" model of JSON tree.
The general model of this DSL is about switching between contexts.
-}
module AesonValueParser
( Value,
run,
runWithTextError,
runAsValueParser,
Error.Error (..),
parseByteString,
-- * Value parsers
object,
array,
null,
nullable,
nullableMonoid,
string,
number,
bool,
fromJSON,
-- * String parsers
String,
text,
mappedText,
narrowedText,
matchedText,
attoparsedText,
megaparsedText,
-- * Number parsers
Number,
scientific,
integer,
floating,
matchedScientific,
matchedInteger,
matchedFloating,
-- * Object parsers
Object,
field,
oneOfFields,
fieldMap,
foldlFields,
fieldsAmount,
-- * Array parsers
Array,
element,
elementVector,
elementList,
foldlElements,
foldrElements,
elementsAmount,
)
where
import qualified AesonValueParser.Error as Error
import AesonValueParser.Prelude hiding (String, bool, null)
import qualified AesonValueParser.Vector as Vector
import qualified Data.Aeson as Aeson
import qualified Data.Aeson.Key as Key
import qualified Data.Aeson.KeyMap as KeyMap
import qualified Data.Aeson.Types as Aeson
import qualified Data.Attoparsec.Text as Attoparsec
import qualified Data.HashMap.Strict as HashMap
import qualified Data.HashSet as HashSet
import qualified Data.Scientific as Scientific
import qualified Data.Text as Text
import qualified Data.Text.Encoding as Text
import qualified Data.Vector as Vector
import qualified Text.Megaparsec as Megaparsec
-- * Value
-- |
-- JSON `Aeson.Value` AST parser.
--
-- Its `Alternative` instance implements the logic of choosing between the possible types of JSON values.
newtype Value a
= Value (ReaderT Aeson.Value (MaybeT (Either Error.Error)) a)
deriving (Functor, Applicative)
-- |
-- Implements the logic of choosing between the possible types of JSON values.
--
-- If you have multiple parsers of the same type of JSON value composed,
-- only the leftmost will be affective.
-- The errors from deeper parsers do not trigger the alternation,
-- instead they get propagated to the top.
instance Alternative Value where
empty = Value $ ReaderT $ const $ MaybeT $ return Nothing
(<|>) (Value leftParser) (Value rightParser) = Value (leftParser <|> rightParser)
{-# INLINE run #-}
run :: Value a -> Aeson.Value -> Either Error.Error a
run = \(Value parser) value -> (=<<) (maybe (Left (typeError value)) Right) $ runMaybeT $ runReaderT parser value
where
typeError = \case
Aeson.Array _ -> "Unexpected type: array"
Aeson.Object _ -> "Unexpected type: object"
Aeson.String _ -> "Unexpected type: string"
Aeson.Number _ -> "Unexpected type: number"
Aeson.Bool _ -> "Unexpected type: bool"
Aeson.Null -> "Unexpected type: null"
{-# INLINE runWithTextError #-}
runWithTextError :: Value a -> Aeson.Value -> Either Text a
runWithTextError parser = left Error.toText . run parser
-- | Convert into a function directly applicable as definition
-- of 'Aeson.parseJSON'.
--
-- Here's an example of how it can be used:
--
-- @
-- data Artist = Artist
-- { artistName :: Text,
-- artistGenres :: [Text]
-- }
--
-- instance 'Aeson.FromJSON' Artist where
-- 'Aeson.parseJSON' = 'runAsValueParser' $
-- 'object' $ do
-- name <- 'field' "name" $ 'string' 'text'
-- genres <- 'field' "genres" $ 'array' $ 'elementList' $ 'string' 'text'
-- return $ Artist name genres
-- @
runAsValueParser :: Value a -> Aeson.Value -> Aeson.Parser a
runAsValueParser parser =
either (fail . Text.unpack) return
. runWithTextError parser
runString :: String a -> Text -> Either (Maybe Text) a
runString (String a) b = first getLast (runExcept (runReaderT a b))
parseByteString :: Value a -> ByteString -> Either Text a
parseByteString p bs =
case Aeson.eitherDecodeStrict' bs of
Right aeson -> runWithTextError p aeson
Left stringErr -> Left (fromString stringErr)
-- ** Definitions
{-# INLINE array #-}
array :: Array a -> Value a
array (Array parser) = Value $
ReaderT $ \case
Aeson.Array x -> lift $ join $ runExcept $ runExceptT $ runReaderT parser x
_ -> empty
{-# INLINE object #-}
object :: Object a -> Value a
object (Object parser) = Value $
ReaderT $ \case
Aeson.Object x -> lift $ join $ runExcept $ runExceptT $ runReaderT parser x
_ -> empty
{-# INLINE null #-}
null :: Value ()
null = Value $
ReaderT $ \case
Aeson.Null -> pure ()
_ -> empty
{-# INLINE nullable #-}
nullable :: Value a -> Value (Maybe a)
nullable (Value parser) = Value $
ReaderT $ \case
Aeson.Null -> pure Nothing
x -> fmap Just (runReaderT parser x)
{-# INLINE nullableMonoid #-}
nullableMonoid :: Monoid a => Value a -> Value a
nullableMonoid (Value parser) = Value $
ReaderT $ \case
Aeson.Null -> pure mempty
x -> runReaderT parser x
{-# INLINE string #-}
string :: String a -> Value a
string (String parser) = Value $
ReaderT $ \case
Aeson.String x -> lift $ left (Error.message . fromMaybe "No details" . getLast) $ runExcept $ runReaderT parser x
_ -> empty
{-# INLINE number #-}
number :: Number a -> Value a
number (Number parser) = Value $
ReaderT $ \case
Aeson.Number x -> lift $ left (Error.message . fromMaybe "No details" . getLast) $ runExcept $ runReaderT parser x
_ -> empty
{-# INLINE bool #-}
bool :: Value Bool
bool = Value $
ReaderT $ \case
Aeson.Bool x -> return x
_ -> empty
{-# INLINE fromJSON #-}
fromJSON :: Aeson.FromJSON a => Value a
fromJSON =
Value $
ReaderT $
Aeson.fromJSON >>> \case
Aeson.Success r -> return r
Aeson.Error m -> lift $ Left $ fromString m
-- * String parsers
newtype String a
= String (ReaderT Text (Except (Last Text)) a)
deriving (Functor, Applicative, Alternative)
{-# INLINE text #-}
text :: String Text
text = String ask
{-# INLINE mappedText #-}
mappedText :: [(Text, a)] -> String a
mappedText mappingList =
let expectedValuesText = fromString (show (fmap fst mappingList))
match lookup text = case lookup text of
Just a -> Right a
_ -> Left ("Unexpected value: \"" <> text <> "\". Expecting one of: " <> expectedValuesText)
mappingListLength = length mappingList
in if mappingListLength > 512
then
let !hashMap = HashMap.fromList mappingList
in matchedText (match (flip HashMap.lookup hashMap))
else matchedText (match (flip lookup mappingList))
{-# INLINE narrowedText #-}
narrowedText :: (Text -> Maybe a) -> String a
narrowedText narrow = matchedText match
where
match text = case narrow text of
Just a -> Right a
_ -> Left ("Unexpected value: \"" <> text <> "\"")
{-# INLINE matchedText #-}
matchedText :: (Text -> Either Text a) -> String a
matchedText parser = String $ ReaderT $ except . left (Last . Just) . parser
{-# INLINE attoparsedText #-}
attoparsedText :: Attoparsec.Parser a -> String a
attoparsedText parser = matchedText $ left fromString . Attoparsec.parseOnly parser
{-# INLINE megaparsedText #-}
megaparsedText :: Megaparsec.Parsec Void Text a -> String a
megaparsedText = matchedText . matcher
where
matcher :: Megaparsec.Parsec Void Text a -> Text -> Either Text a
matcher p = left (fromString . Megaparsec.errorBundlePretty) . Megaparsec.runParser (p <* Megaparsec.eof) ""
-- * Number parsers
newtype Number a
= Number (ReaderT Scientific (Except (Last Text)) a)
deriving (Functor, Applicative, Alternative)
{-# INLINE scientific #-}
scientific :: Number Scientific
scientific = Number ask
{-# INLINE integer #-}
integer :: (Integral a, Bounded a) => Number a
integer = Number $
ReaderT $ \x ->
if Scientific.isInteger x
then case Scientific.toBoundedInteger x of
Just int -> return int
Nothing -> throwError (Last (Just (fromString ("Number " <> show x <> " is out of integer range"))))
else throwError (Last (Just (fromString ("Number " <> show x <> " is not integer"))))
{-# INLINE floating #-}
floating :: RealFloat a => Number a
floating = Number $
ReaderT $ \a -> case Scientific.toBoundedRealFloat a of
Right b -> return b
Left c ->
if c == 0
then throwError (Last (Just (fromString ("Number " <> show a <> " is too small"))))
else throwError (Last (Just (fromString ("Number " <> show a <> " is too large"))))
{-# INLINE matchedScientific #-}
matchedScientific :: (Scientific -> Either Text a) -> Number a
matchedScientific matcher = Number $ ReaderT $ except . left (Last . Just) . matcher
{-# INLINE matchedInteger #-}
matchedInteger :: (Integral integer, Bounded integer) => (integer -> Either Text a) -> Number a
matchedInteger matcher = Number $ case integer of
Number parser -> parser >>= either (throwError . Last . Just) return . matcher
{-# INLINE matchedFloating #-}
matchedFloating :: RealFloat floating => (floating -> Either Text a) -> Number a
matchedFloating matcher = Number $ case floating of
Number parser -> parser >>= either (throwError . Last . Just) return . matcher
-- * Object parsers
-- |
-- JSON `Aeson.Object` parser.
newtype Object a
= Object (ReaderT (KeyMap.KeyMap Aeson.Value) (ExceptT Error.Error (Except Error.Error)) a)
deriving (Functor, Applicative, Alternative, Monad, MonadPlus, MonadError Error.Error)
instance MonadFail Object where
fail = throwError . fromString
{-# INLINE field #-}
field :: Text -> Value a -> Object a
field name fieldParser = Object $
ReaderT $ \object -> case KeyMap.lookup (Key.fromText name) object of
Just value -> case run fieldParser value of
Right parsedValue -> return parsedValue
Left error -> lift $ throwE $ Error.named name error
Nothing -> throwE (Error.Error (pure name) message)
where
message =
"Object contains no field with this name. Fields available: "
<> fromString (show (KeyMap.keys object))
{-# INLINE oneOfFields #-}
oneOfFields :: [Text] -> Value a -> Object a
oneOfFields keys valueParser = asum (fmap (flip field valueParser) keys)
{-# INLINE fieldMap #-}
fieldMap :: (Eq a, Hashable a) => String a -> Value b -> Object (HashMap a b)
fieldMap keyParser fieldParser = Object $ ReaderT $ fmap HashMap.fromList . traverse mapping . KeyMap.toList
where
mapping (key, ast) =
case Key.toText key of
keyText -> case runString keyParser keyText of
Right parsedKey -> case run fieldParser ast of
Right parsedField -> return (parsedKey, parsedField)
Left error -> lift (throwE (Error.named keyText error))
Left error -> lift (throwE (maybe mempty Error.message error))
{-# INLINE foldlFields #-}
foldlFields :: (state -> key -> field -> state) -> state -> String key -> Value field -> Object state
foldlFields step state keyParser fieldParser = Object $
ReaderT $ \object ->
KeyMap.foldrWithKey newStep pure object state
where
newStep key value next !state =
case Key.toText key of
key -> case runString keyParser key of
Right parsedKey -> case run fieldParser value of
Right parsedValue -> next (step state parsedKey parsedValue)
Left error -> lift $ throwE $ Error.named key error
Left error -> lift (throwE (maybe mempty Error.message error))
fieldsAmount :: Object Int
fieldsAmount = Object $ ReaderT $ pure . KeyMap.size
-- * Array parsers
-- |
-- JSON `Aeson.Array` parser.
newtype Array a
= Array (ReaderT (Vector Aeson.Value) (ExceptT Error.Error (Except Error.Error)) a)
deriving (Functor, Applicative, Alternative, Monad, MonadPlus, MonadError Error.Error)
instance MonadFail Array where
fail = throwError . fromString
{-# INLINE element #-}
element :: Int -> Value a -> Array a
element index elementParser = Array $
ReaderT $ \array -> case array Vector.!? index of
Just element -> case run elementParser element of
Right result -> return result
Left error -> lift $ throwE $ Error.indexed index error
Nothing -> throwE $ Error.Error (pure (fromString (show index))) "Array contains no element by this index"
{-# INLINE elementVector #-}
elementVector :: Value a -> Array (Vector a)
elementVector elementParser = Array $
ReaderT $ \arrayAst -> flip Vector.imapM arrayAst $ \index ast -> case run elementParser ast of
Right element -> return element
Left error -> lift $ throwE $ Error.indexed index error
{-# INLINE elementList #-}
elementList :: Value a -> Array [a]
elementList = fmap Vector.toList . elementVector
{-# INLINE foldlElements #-}
foldlElements :: (state -> Int -> element -> state) -> state -> Value element -> Array state
foldlElements step state elementParser = Array $ ReaderT $ Vector.ifoldM' newStep state
where
newStep state index ast = case run elementParser ast of
Right element -> return $ step state index element
Left error -> lift $ throwE $ Error.indexed index error
{-# INLINE foldrElements #-}
foldrElements :: (Int -> element -> state -> state) -> state -> Value element -> Array state
foldrElements step state elementParser = Array $ ReaderT $ Vector.ifoldrM newStep state
where
newStep index ast nextState = case run elementParser ast of
Right element -> return $ step index element nextState
Left error -> lift $ throwE $ Error.indexed index error
elementsAmount :: Array Int
elementsAmount = Array $ ReaderT $ pure . Vector.length