{-# LANGUAGE CPP, DefaultSignatures, EmptyDataDecls, FlexibleInstances,
    FunctionalDependencies, KindSignatures, OverlappingInstances,
    ScopedTypeVariables, TypeOperators, UndecidableInstances,
    ViewPatterns, NamedFieldPuns, FlexibleContexts, PatternGuards,
    RecordWildCards #-}
{-# OPTIONS_GHC -fno-warn-orphans #-}

-- |
-- Module:      Data.Aeson.Types.Generic
-- Copyright:   (c) 2012 Bryan O'Sullivan
--              (c) 2011, 2012 Bas Van Dijk
--              (c) 2011 MailRank, Inc.
-- License:     Apache
-- Maintainer:  Bryan O'Sullivan <bos@serpentine.com>
-- Stability:   experimental
-- Portability: portable
--
-- Types for working with JSON data.

module Data.Aeson.Types.Generic ( ) where

import Control.Applicative ((<*>), (<$>), (<|>), pure)
import Control.Monad ((<=<))
import Control.Monad.ST (ST)
import Data.Aeson.Types.Class
import Data.Aeson.Types.Internal
import Data.Bits
import Data.DList (DList, toList, empty)
import Data.Maybe (fromMaybe)
import Data.Monoid (mappend)
import Data.Text (Text, pack, unpack)
import GHC.Generics
import qualified Data.HashMap.Strict as H
import qualified Data.Vector as V
import qualified Data.Vector.Mutable as VM

--------------------------------------------------------------------------------
-- Generic toJSON

instance (GToJSON a) => GToJSON (M1 i c a) where
    -- Meta-information, which is not handled elsewhere, is ignored:
    gToJSON opts = gToJSON opts . unM1
    {-# INLINE gToJSON #-}

instance (ToJSON a) => GToJSON (K1 i a) where
    -- Constant values are encoded using their ToJSON instance:
    gToJSON _opts = toJSON . unK1
    {-# INLINE gToJSON #-}

instance GToJSON U1 where
    -- Empty constructors are encoded to an empty array:
    gToJSON _opts _ = emptyArray
    {-# INLINE gToJSON #-}

instance (ConsToJSON a) => GToJSON (C1 c a) where
    -- Constructors need to be encoded differently depending on whether they're
    -- a record or not. This distinction is made by 'constToJSON':
    gToJSON opts = consToJSON opts . unM1
    {-# INLINE gToJSON #-}

instance ( WriteProduct a, WriteProduct b
         , ProductSize  a, ProductSize  b ) => GToJSON (a :*: b) where
    -- Products are encoded to an array. Here we allocate a mutable vector of
    -- the same size as the product and write the product's elements to it using
    -- 'writeProduct':
    gToJSON opts p =
        Array $ V.create $ do
          mv <- VM.unsafeNew lenProduct
          writeProduct opts mv 0 lenProduct p
          return mv
        where
          lenProduct = (unTagged2 :: Tagged2 (a :*: b) Int -> Int)
                       productSize
    {-# INLINE gToJSON #-}

instance ( AllNullary (a :+: b) allNullary
         , SumToJSON  (a :+: b) allNullary ) => GToJSON (a :+: b) where
    -- If all constructors of a sum datatype are nullary and the
    -- 'allNullaryToStringTag' option is set they are encoded to
    -- strings.  This distinction is made by 'sumToJSON':
    gToJSON opts = (unTagged :: Tagged allNullary Value -> Value)
                 . sumToJSON opts
    {-# INLINE gToJSON #-}

--------------------------------------------------------------------------------

class SumToJSON f allNullary where
    sumToJSON :: Options -> f a -> Tagged allNullary Value

instance ( GetConName            f
         , TaggedObject          f
         , ObjectWithSingleField f
         , TwoElemArray          f ) => SumToJSON f True where
    sumToJSON opts
        | allNullaryToStringTag opts = Tagged . String . pack
                                     . constructorTagModifier opts . getConName
        | otherwise = Tagged . nonAllNullarySumToJSON opts
    {-# INLINE sumToJSON #-}

instance ( TwoElemArray          f
         , TaggedObject          f
         , ObjectWithSingleField f ) => SumToJSON f False where
    sumToJSON opts = Tagged . nonAllNullarySumToJSON opts
    {-# INLINE sumToJSON #-}

nonAllNullarySumToJSON :: ( TwoElemArray          f
                          , TaggedObject          f
                          , ObjectWithSingleField f
                          ) => Options -> f a -> Value
nonAllNullarySumToJSON opts =
    case sumEncoding opts of
      TaggedObject{..}      -> object . taggedObject opts tagFieldName
                                                          contentsFieldName
      ObjectWithSingleField -> Object . objectWithSingleField opts
      TwoElemArray          -> Array  . twoElemArray opts
{-# INLINE nonAllNullarySumToJSON #-}

--------------------------------------------------------------------------------

class TaggedObject f where
    taggedObject :: Options -> String -> String -> f a -> [Pair]

instance ( TaggedObject a
         , TaggedObject b ) => TaggedObject (a :+: b) where
    taggedObject     opts tagFieldName contentsFieldName (L1 x) =
        taggedObject opts tagFieldName contentsFieldName     x
    taggedObject     opts tagFieldName contentsFieldName (R1 x) =
        taggedObject opts tagFieldName contentsFieldName     x
    {-# INLINE taggedObject #-}

instance ( IsRecord      a isRecord
         , TaggedObject' a isRecord
         , Constructor c ) => TaggedObject (C1 c a) where
    taggedObject opts tagFieldName contentsFieldName =
        (pack tagFieldName .= constructorTagModifier opts
                                 (conName (undefined :: t c a p)) :) .
        (unTagged :: Tagged isRecord [Pair] -> [Pair]) .
          taggedObject' opts contentsFieldName . unM1
    {-# INLINE taggedObject #-}

class TaggedObject' f isRecord where
    taggedObject' :: Options -> String -> f a -> Tagged isRecord [Pair]

instance (RecordToPairs f) => TaggedObject' f True where
    taggedObject' opts _ = Tagged . toList . recordToPairs opts
    {-# INLINE taggedObject' #-}

instance (GToJSON f) => TaggedObject' f False where
    taggedObject' opts contentsFieldName =
        Tagged . (:[]) . (pack contentsFieldName .=) . gToJSON opts
    {-# INLINE taggedObject' #-}

--------------------------------------------------------------------------------

-- | Get the name of the constructor of a sum datatype.
class GetConName f where
    getConName :: f a -> String

instance (GetConName a, GetConName b) => GetConName (a :+: b) where
    getConName (L1 x) = getConName x
    getConName (R1 x) = getConName x
    {-# INLINE getConName #-}

instance (Constructor c, GToJSON a, ConsToJSON a) => GetConName (C1 c a) where
    getConName = conName
    {-# INLINE getConName #-}

--------------------------------------------------------------------------------

class TwoElemArray f where
    twoElemArray :: Options -> f a -> V.Vector Value

instance (TwoElemArray a, TwoElemArray b) => TwoElemArray (a :+: b) where
    twoElemArray opts (L1 x) = twoElemArray opts x
    twoElemArray opts (R1 x) = twoElemArray opts x
    {-# INLINE twoElemArray #-}

instance ( GToJSON a, ConsToJSON a
         , Constructor c ) => TwoElemArray (C1 c a) where
    twoElemArray opts x = V.create $ do
      mv <- VM.unsafeNew 2
      VM.unsafeWrite mv 0 $ String $ pack $ constructorTagModifier opts
                                   $ conName (undefined :: t c a p)
      VM.unsafeWrite mv 1 $ gToJSON opts x
      return mv
    {-# INLINE twoElemArray #-}

--------------------------------------------------------------------------------

class ConsToJSON f where
    consToJSON  :: Options -> f a -> Value

class ConsToJSON' f isRecord where
    consToJSON' :: Options -> f a -> Tagged isRecord Value

instance ( IsRecord    f isRecord
         , ConsToJSON' f isRecord ) => ConsToJSON f where
    consToJSON opts = (unTagged :: Tagged isRecord Value -> Value)
                    . consToJSON' opts
    {-# INLINE consToJSON #-}

instance (RecordToPairs f) => ConsToJSON' f True where
    consToJSON' opts = Tagged . object . toList . recordToPairs opts
    {-# INLINE consToJSON' #-}

instance GToJSON f => ConsToJSON' f False where
    consToJSON' opts = Tagged . gToJSON opts
    {-# INLINE consToJSON' #-}

--------------------------------------------------------------------------------

class RecordToPairs f where
    recordToPairs :: Options -> f a -> DList Pair

instance (RecordToPairs a, RecordToPairs b) => RecordToPairs (a :*: b) where
    recordToPairs opts (a :*: b) = recordToPairs opts a `mappend`
                                   recordToPairs opts b
    {-# INLINE recordToPairs #-}

instance (Selector s, GToJSON a) => RecordToPairs (S1 s a) where
    recordToPairs = fieldToPair
    {-# INLINE recordToPairs #-}

instance (Selector s, ToJSON a) => RecordToPairs (S1 s (K1 i (Maybe a))) where
    recordToPairs opts (M1 k1) | omitNothingFields opts
                               , K1 Nothing <- k1 = empty
    recordToPairs opts m1 = fieldToPair opts m1
    {-# INLINE recordToPairs #-}

fieldToPair :: (Selector s, GToJSON a) => Options -> S1 s a p -> DList Pair
fieldToPair opts m1 = pure ( pack $ fieldLabelModifier opts $ selName m1
                           , gToJSON opts (unM1 m1)
                           )
{-# INLINE fieldToPair #-}

--------------------------------------------------------------------------------

class WriteProduct f where
    writeProduct :: Options
                 -> VM.MVector s Value
                 -> Int -- ^ index
                 -> Int -- ^ length
                 -> f a
                 -> ST s ()

instance ( WriteProduct a
         , WriteProduct b ) => WriteProduct (a :*: b) where
    writeProduct opts mv ix len (a :*: b) = do
      writeProduct opts mv ix  lenL a
      writeProduct opts mv ixR lenR b
        where
#if MIN_VERSION_base(4,5,0)
          lenL = len `unsafeShiftR` 1
#else
          lenL = len `shiftR` 1
#endif
          lenR = len - lenL
          ixR  = ix  + lenL
    {-# INLINE writeProduct #-}

instance (GToJSON a) => WriteProduct a where
    writeProduct opts mv ix _ = VM.unsafeWrite mv ix . gToJSON opts
    {-# INLINE writeProduct #-}

--------------------------------------------------------------------------------

class ObjectWithSingleField f where
    objectWithSingleField :: Options -> f a -> Object

instance ( ObjectWithSingleField a
         , ObjectWithSingleField b ) => ObjectWithSingleField (a :+: b) where
    objectWithSingleField opts (L1 x) = objectWithSingleField opts x
    objectWithSingleField opts (R1 x) = objectWithSingleField opts x
    {-# INLINE objectWithSingleField #-}

instance ( GToJSON a, ConsToJSON a
         , Constructor c ) => ObjectWithSingleField (C1 c a) where
    objectWithSingleField opts = H.singleton typ . gToJSON opts
        where
          typ = pack $ constructorTagModifier opts $
                         conName (undefined :: t c a p)
    {-# INLINE objectWithSingleField #-}

--------------------------------------------------------------------------------
-- Generic parseJSON

instance (GFromJSON a) => GFromJSON (M1 i c a) where
    -- Meta-information, which is not handled elsewhere, is just added to the
    -- parsed value:
    gParseJSON opts = fmap M1 . gParseJSON opts
    {-# INLINE gParseJSON #-}

instance (FromJSON a) => GFromJSON (K1 i a) where
    -- Constant values are decoded using their FromJSON instance:
    gParseJSON _opts = fmap K1 . parseJSON
    {-# INLINE gParseJSON #-}

instance GFromJSON U1 where
    -- Empty constructors are expected to be encoded as an empty array:
    gParseJSON _opts v
        | isEmptyArray v = pure U1
        | otherwise      = typeMismatch "unit constructor (U1)" v
    {-# INLINE gParseJSON #-}

instance (ConsFromJSON a) => GFromJSON (C1 c a) where
    -- Constructors need to be decoded differently depending on whether they're
    -- a record or not. This distinction is made by consParseJSON:
    gParseJSON opts = fmap M1 . consParseJSON opts
    {-# INLINE gParseJSON #-}

instance ( FromProduct a, FromProduct b
         , ProductSize a, ProductSize b ) => GFromJSON (a :*: b) where
    -- Products are expected to be encoded to an array. Here we check whether we
    -- got an array of the same size as the product, then parse each of the
    -- product's elements using parseProduct:
    gParseJSON opts = withArray "product (:*:)" $ \arr ->
      let lenArray = V.length arr
          lenProduct = (unTagged2 :: Tagged2 (a :*: b) Int -> Int)
                       productSize in
      if lenArray == lenProduct
      then parseProduct opts arr 0 lenProduct
      else fail $ "When expecting a product of " ++ show lenProduct ++
                  " values, encountered an Array of " ++ show lenArray ++
                  " elements instead"
    {-# INLINE gParseJSON #-}

instance ( AllNullary (a :+: b) allNullary
         , ParseSum   (a :+: b) allNullary ) => GFromJSON   (a :+: b) where
    -- If all constructors of a sum datatype are nullary and the
    -- 'allNullaryToStringTag' option is set they are expected to be
    -- encoded as strings.  This distinction is made by 'parseSum':
    gParseJSON opts = (unTagged :: Tagged allNullary (Parser ((a :+: b) d)) ->
                                                     (Parser ((a :+: b) d)))
                    . parseSum opts
    {-# INLINE gParseJSON #-}

--------------------------------------------------------------------------------

class ParseSum f allNullary where
    parseSum :: Options -> Value -> Tagged allNullary (Parser (f a))

instance ( SumFromString    (a :+: b)
         , FromPair         (a :+: b)
         , FromTaggedObject (a :+: b) ) => ParseSum (a :+: b) True where
    parseSum opts
        | allNullaryToStringTag opts = Tagged . parseAllNullarySum    opts
        | otherwise                  = Tagged . parseNonAllNullarySum opts
    {-# INLINE parseSum #-}

instance ( FromPair         (a :+: b)
         , FromTaggedObject (a :+: b) ) => ParseSum (a :+: b) False where
    parseSum opts = Tagged . parseNonAllNullarySum opts
    {-# INLINE parseSum #-}

--------------------------------------------------------------------------------

parseAllNullarySum :: SumFromString f => Options -> Value -> Parser (f a)
parseAllNullarySum opts = withText "Text" $ \key ->
                            maybe (notFound $ unpack key) return $
                              parseSumFromString opts key
{-# INLINE parseAllNullarySum #-}

class SumFromString f where
    parseSumFromString :: Options -> Text -> Maybe (f a)

instance (SumFromString a, SumFromString b) => SumFromString (a :+: b) where
    parseSumFromString opts key = (L1 <$> parseSumFromString opts key) <|>
                                  (R1 <$> parseSumFromString opts key)
    {-# INLINE parseSumFromString #-}

instance (Constructor c) => SumFromString (C1 c U1) where
    parseSumFromString opts key | key == name = Just $ M1 U1
                                | otherwise   = Nothing
        where
          name = pack $ constructorTagModifier opts $
                          conName (undefined :: t c U1 p)
    {-# INLINE parseSumFromString #-}

--------------------------------------------------------------------------------

parseNonAllNullarySum :: ( FromPair                       (a :+: b)
                         , FromTaggedObject               (a :+: b)
                         ) => Options -> Value -> Parser ((a :+: b) c)
parseNonAllNullarySum opts =
    case sumEncoding opts of
      TaggedObject{..} ->
          withObject "Object" $ \obj -> do
            tag <- obj .: pack tagFieldName
            fromMaybe (notFound $ unpack tag) $
              parseFromTaggedObject opts contentsFieldName obj tag

      ObjectWithSingleField ->
          withObject "Object" $ \obj ->
            case H.toList obj of
              [pair@(tag, _)] -> fromMaybe (notFound $ unpack tag) $
                                   parsePair opts pair
              _ -> fail "Object doesn't have a single field"

      TwoElemArray ->
          withArray "Array" $ \arr ->
            if V.length arr == 2
            then case V.unsafeIndex arr 0 of
                   String tag -> fromMaybe (notFound $ unpack tag) $
                                   parsePair opts (tag, V.unsafeIndex arr 1)
                   _ -> fail "First element is not a String"
            else fail "Array doesn't have 2 elements"
{-# INLINE parseNonAllNullarySum #-}

--------------------------------------------------------------------------------

class FromTaggedObject f where
    parseFromTaggedObject :: Options -> String -> Object -> Text
                          -> Maybe (Parser (f a))

instance (FromTaggedObject a, FromTaggedObject b) =>
    FromTaggedObject (a :+: b) where
        parseFromTaggedObject opts contentsFieldName obj tag =
            (fmap L1 <$> parseFromTaggedObject opts contentsFieldName obj tag) <|>
            (fmap R1 <$> parseFromTaggedObject opts contentsFieldName obj tag)
        {-# INLINE parseFromTaggedObject #-}

instance ( FromTaggedObject' f
         , Constructor c ) => FromTaggedObject (C1 c f) where
    parseFromTaggedObject opts contentsFieldName obj tag
        | tag == name = Just $ M1 <$> parseFromTaggedObject'
                                        opts contentsFieldName obj
        | otherwise = Nothing
        where
          name = pack $ constructorTagModifier opts $
                          conName (undefined :: t c f p)
    {-# INLINE parseFromTaggedObject #-}

--------------------------------------------------------------------------------

class FromTaggedObject' f where
    parseFromTaggedObject' :: Options -> String -> Object -> Parser (f a)

class FromTaggedObject'' f isRecord where
    parseFromTaggedObject'' :: Options -> String -> Object
                            -> Tagged isRecord (Parser (f a))

instance ( IsRecord             f isRecord
         , FromTaggedObject''   f isRecord
         ) => FromTaggedObject' f where
    parseFromTaggedObject' opts contentsFieldName =
        (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a)) .
        parseFromTaggedObject'' opts contentsFieldName
    {-# INLINE parseFromTaggedObject' #-}

instance (FromRecord f) => FromTaggedObject'' f True where
    parseFromTaggedObject'' opts _ = Tagged . parseRecord opts
    {-# INLINE parseFromTaggedObject'' #-}

instance (GFromJSON f) => FromTaggedObject'' f False where
    parseFromTaggedObject'' opts contentsFieldName = Tagged .
      (gParseJSON opts <=< (.: pack contentsFieldName))
    {-# INLINE parseFromTaggedObject'' #-}

--------------------------------------------------------------------------------

class ConsFromJSON f where
    consParseJSON  :: Options -> Value -> Parser (f a)

class ConsFromJSON' f isRecord where
    consParseJSON' :: Options -> Value -> Tagged isRecord (Parser (f a))

instance ( IsRecord        f isRecord
         , ConsFromJSON'   f isRecord
         ) => ConsFromJSON f where
    consParseJSON opts = (unTagged :: Tagged isRecord (Parser (f a)) -> Parser (f a))
                       . consParseJSON' opts
    {-# INLINE consParseJSON #-}

instance (FromRecord f) => ConsFromJSON' f True where
    consParseJSON' opts = Tagged . (withObject "record (:*:)" $ parseRecord opts)
    {-# INLINE consParseJSON' #-}

instance (GFromJSON f) => ConsFromJSON' f False where
    consParseJSON' opts = Tagged . gParseJSON opts
    {-# INLINE consParseJSON' #-}

--------------------------------------------------------------------------------

class FromRecord f where
    parseRecord :: Options -> Object -> Parser (f a)

instance (FromRecord a, FromRecord b) => FromRecord (a :*: b) where
    parseRecord opts obj = (:*:) <$> parseRecord opts obj
                                 <*> parseRecord opts obj
    {-# INLINE parseRecord #-}

instance (Selector s, GFromJSON a) => FromRecord (S1 s a) where
    parseRecord opts = maybe (notFound label) (gParseJSON opts)
                      . H.lookup (pack label)
        where
          label = fieldLabelModifier opts $ selName (undefined :: t s a p)
    {-# INLINE parseRecord #-}

instance (Selector s, FromJSON a) => FromRecord (S1 s (K1 i (Maybe a))) where
    parseRecord opts obj = (M1 . K1) <$> obj .:? pack label
        where
          label = fieldLabelModifier opts $
                    selName (undefined :: t s (K1 i (Maybe a)) p)
    {-# INLINE parseRecord #-}

--------------------------------------------------------------------------------

class ProductSize f where
    productSize :: Tagged2 f Int

instance (ProductSize a, ProductSize b) => ProductSize (a :*: b) where
    productSize = Tagged2 $ unTagged2 (productSize :: Tagged2 a Int) +
                            unTagged2 (productSize :: Tagged2 b Int)
    {-# INLINE productSize #-}

instance ProductSize (S1 s a) where
    productSize = Tagged2 1
    {-# INLINE productSize #-}

--------------------------------------------------------------------------------

class FromProduct f where
    parseProduct :: Options -> Array -> Int -> Int -> Parser (f a)

instance (FromProduct a, FromProduct b) => FromProduct (a :*: b) where
    parseProduct opts arr ix len =
        (:*:) <$> parseProduct opts arr ix  lenL
              <*> parseProduct opts arr ixR lenR
        where
#if MIN_VERSION_base(4,5,0)
          lenL = len `unsafeShiftR` 1
#else
          lenL = len `shiftR` 1
#endif
          ixR  = ix + lenL
          lenR = len - lenL
    {-# INLINE parseProduct #-}

instance (GFromJSON a) => FromProduct (S1 s a) where
    parseProduct opts arr ix _ = gParseJSON opts $ V.unsafeIndex arr ix
    {-# INLINE parseProduct #-}

--------------------------------------------------------------------------------

class FromPair f where
    parsePair :: Options -> Pair -> Maybe (Parser (f a))

instance (FromPair a, FromPair b) => FromPair (a :+: b) where
    parsePair opts pair = (fmap L1 <$> parsePair opts pair) <|>
                          (fmap R1 <$> parsePair opts pair)
    {-# INLINE parsePair #-}

instance (Constructor c, GFromJSON a, ConsFromJSON a) => FromPair (C1 c a) where
    parsePair opts (tag, value)
        | tag == tag' = Just $ gParseJSON opts value
        | otherwise   = Nothing
        where
          tag' = pack $ constructorTagModifier opts $
                          conName (undefined :: t c a p)
    {-# INLINE parsePair #-}

--------------------------------------------------------------------------------

class IsRecord (f :: * -> *) isRecord | f -> isRecord

instance (IsRecord f isRecord) => IsRecord (f :*: g) isRecord
instance IsRecord (M1 S NoSelector f) False
instance (IsRecord f isRecord) => IsRecord (M1 S c f) isRecord
instance IsRecord (K1 i c) True
instance IsRecord U1 False

--------------------------------------------------------------------------------

class AllNullary (f :: * -> *) allNullary | f -> allNullary

instance ( AllNullary a allNullaryL
         , AllNullary b allNullaryR
         , And allNullaryL allNullaryR allNullary
         ) => AllNullary (a :+: b) allNullary
instance AllNullary a allNullary => AllNullary (M1 i c a) allNullary
instance AllNullary (a :*: b) False
instance AllNullary (K1 i c) False
instance AllNullary U1 True

--------------------------------------------------------------------------------

data True
data False

class    And bool1 bool2 bool3 | bool1 bool2 -> bool3

instance And True  True  True
instance And False False False
instance And False True  False
instance And True  False False

--------------------------------------------------------------------------------

newtype Tagged s b = Tagged {unTagged :: b}

newtype Tagged2 (s :: * -> *) b = Tagged2 {unTagged2 :: b}

--------------------------------------------------------------------------------

notFound :: String -> Parser a
notFound key = fail $ "The key \"" ++ key ++ "\" was not found"
{-# INLINE notFound #-}
