{-|
Module      :  HsLua.Aeson
Copyright   :  © 2017–2021 Albert Krewinkel
License     :  MIT
Maintainer  :  Albert Krewinkel <tarleb@zeitkraut.de>

Pushes and retrieves aeson `Value`s to and from the Lua stack.

- JSON @null@ values are encoded as light userdata containing the
  @NULL@ pointer.

- Objects are converted to string-indexed tables.

- Arrays are converted to sequence tables and are given a
  metatable. This makes it possible to distinguish between empty
  arrays and empty objects. The metatable is stored in the
  registry under key @\'HsLua JSON array\'@' (see also
  'jsonarray').

- JSON numbers are converted to Lua numbers, i.e., 'Lua.Number';
  the exact C type may vary, depending on compile-time Lua
  configuration.
-}
module HsLua.Aeson
  ( peekValue
  , pushValue
  , peekViaJSON
  , pushViaJSON
  ) where

import Control.Monad ((<$!>), void)
import Data.Scientific (toRealFloat, fromFloatDigits)
import Foreign.Ptr (nullPtr)
import HsLua.Core as Lua
import HsLua.Marshalling as Lua

import qualified Data.Aeson as Aeson
import qualified Data.ByteString as B
import qualified Data.Vector as Vector
import qualified HsLua.Core.Utf8 as UTF8

#if MIN_VERSION_aeson(2,0,0)
import Data.Aeson.Key (toText, fromText)
import qualified Data.Aeson.KeyMap as KeyMap
#else
import Data.Text (Text)
import qualified Data.HashMap.Strict as KeyMap

toText, fromText :: Text -> Text
toText = id
fromText = id
#endif

-- | Hslua StackValue instance for the Aeson Value data type.
pushValue :: LuaError e => Pusher e Aeson.Value
pushValue :: Pusher e Value
pushValue Value
val = do
  Int -> String -> LuaE e ()
forall e. LuaError e => Int -> String -> LuaE e ()
checkstack' Int
1 String
"HsLua.Aeson.pushValue"
  case Value
val of
    Aeson.Object Object
o -> Pusher e Key -> Pusher e Value -> Pusher e [(Key, Value)]
forall e a b.
LuaError e =>
Pusher e a -> Pusher e b -> Pusher e [(a, b)]
pushKeyValuePairs Pusher e Key
forall e. Key -> LuaE e ()
pushKey Pusher e Value
forall e. LuaError e => Pusher e Value
pushValue Pusher e [(Key, Value)] -> Pusher e [(Key, Value)]
forall a b. (a -> b) -> a -> b
$ Object -> [(Key, Value)]
forall v. KeyMap v -> [(Key, v)]
KeyMap.toList Object
o
    Aeson.Number Scientific
n -> forall e. RealFloat Double => Double -> LuaE e ()
forall a e. RealFloat a => a -> LuaE e ()
pushRealFloat @Double (Double -> LuaE e ()) -> Double -> LuaE e ()
forall a b. (a -> b) -> a -> b
$ Scientific -> Double
forall a. RealFloat a => Scientific -> a
toRealFloat Scientific
n
    Aeson.String Text
s -> Pusher e Text
forall e. Pusher e Text
pushText Text
s
    Aeson.Array Array
a  -> Array -> LuaE e ()
forall e. LuaError e => Array -> LuaE e ()
pushArray Array
a
    Aeson.Bool Bool
b   -> Pusher e Bool
forall e. Pusher e Bool
pushBool Bool
b
    Value
Aeson.Null     -> Ptr Any -> LuaE e ()
forall a e. Ptr a -> LuaE e ()
pushlightuserdata Ptr Any
forall a. Ptr a
nullPtr
 where
  pushKey :: Key -> LuaE e ()
pushKey = Pusher e Text
forall e. Pusher e Text
pushText Pusher e Text -> (Key -> Text) -> Key -> LuaE e ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Key -> Text
toText
  pushArray :: Array -> LuaE e ()
pushArray Array
x = do
    Int -> String -> LuaE e ()
forall e. LuaError e => Int -> String -> LuaE e ()
checkstack' Int
4 String
"HsLua.Aeson.pushVector"
    Pusher e Value -> [Value] -> LuaE e ()
forall e a. LuaError e => Pusher e a -> [a] -> LuaE e ()
pushList Pusher e Value
forall e. LuaError e => Pusher e Value
pushValue ([Value] -> LuaE e ()) -> [Value] -> LuaE e ()
forall a b. (a -> b) -> a -> b
$ Array -> [Value]
forall a. Vector a -> [a]
Vector.toList Array
x
    LuaE e Bool -> LuaE e ()
forall (f :: * -> *) a. Functor f => f a -> f ()
void (LuaE e Bool -> LuaE e ()) -> LuaE e Bool -> LuaE e ()
forall a b. (a -> b) -> a -> b
$ Name -> LuaE e Bool
forall e. Name -> LuaE e Bool
newmetatable Name
jsonarray
    StackIndex -> LuaE e ()
forall e. StackIndex -> LuaE e ()
setmetatable (CInt -> StackIndex
nth CInt
2)

-- | Name of the registry slot holding the metatable given to
-- array tables. The registry entry can be replaced with a
-- different table if needed.
jsonarray :: Name
jsonarray :: Name
jsonarray = Name
"HsLua JSON array"

-- | Retrieves an Aeson 'Aeson.Value' from the Lua stack.
peekValue :: LuaError e => Peeker e Aeson.Value
peekValue :: Peeker e Value
peekValue StackIndex
idx = LuaE e Type -> Peek e Type
forall e a. LuaE e a -> Peek e a
liftLua (StackIndex -> LuaE e Type
forall e. StackIndex -> LuaE e Type
ltype StackIndex
idx) Peek e Type -> (Type -> Peek e Value) -> Peek e Value
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
  Type
TypeBoolean -> Bool -> Value
Aeson.Bool  (Bool -> Value) -> Peek e Bool -> Peek e Value
forall (m :: * -> *) a b. Monad m => (a -> b) -> m a -> m b
<$!> Peeker e Bool
forall e. Peeker e Bool
peekBool StackIndex
idx
  Type
TypeNumber -> Scientific -> Value
Aeson.Number (Scientific -> Value) -> (Double -> Scientific) -> Double -> Value
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Double -> Scientific
forall a. RealFloat a => a -> Scientific
fromFloatDigits (Double -> Value) -> Peek e Double -> Peek e Value
forall (m :: * -> *) a b. Monad m => (a -> b) -> m a -> m b
<$!> Peeker e Double
forall a e. (RealFloat a, Read a) => Peeker e a
peekRealFloat @Double StackIndex
idx
  Type
TypeString -> Text -> Value
Aeson.String (Text -> Value) -> Peek e Text -> Peek e Value
forall (m :: * -> *) a b. Monad m => (a -> b) -> m a -> m b
<$!> Peeker e Text
forall e. Peeker e Text
peekText StackIndex
idx
  Type
TypeLightUserdata -> LuaE e (Maybe (Ptr Any)) -> Peek e (Maybe (Ptr Any))
forall e a. LuaE e a -> Peek e a
liftLua (StackIndex -> LuaE e (Maybe (Ptr Any))
forall e a. StackIndex -> LuaE e (Maybe (Ptr a))
touserdata StackIndex
idx) Peek e (Maybe (Ptr Any))
-> (Maybe (Ptr Any) -> Peek e Value) -> Peek e Value
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
    -- must be the null pointer
    Maybe (Ptr Any)
Nothing -> Value -> Peek e Value
forall (f :: * -> *) a. Applicative f => a -> f a
pure Value
Aeson.Null
    Maybe (Ptr Any)
_       -> Name -> StackIndex -> Peek e ByteString
forall e. Name -> StackIndex -> Peek e ByteString
typeMismatchMessage Name
"null" StackIndex
idx Peek e ByteString -> (ByteString -> Peek e Value) -> Peek e Value
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= ByteString -> Peek e Value
forall a e. ByteString -> Peek e a
failPeek
  Type
TypeNil -> Value -> Peek e Value
forall (m :: * -> *) a. Monad m => a -> m a
return Value
Aeson.Null
  Type
TypeTable -> do
      LuaE e () -> Peek e ()
forall e a. LuaE e a -> Peek e a
liftLua (LuaE e () -> Peek e ()) -> LuaE e () -> Peek e ()
forall a b. (a -> b) -> a -> b
$ Int -> String -> LuaE e ()
forall e. LuaError e => Int -> String -> LuaE e ()
checkstack' Int
2 String
"HsLua.Aeson.peekValue"
      let peekKey :: StackIndex -> Peek e Key
peekKey = (Text -> Key) -> Peek e Text -> Peek e Key
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Text -> Key
fromText (Peek e Text -> Peek e Key)
-> (StackIndex -> Peek e Text) -> StackIndex -> Peek e Key
forall b c a. (b -> c) -> (a -> b) -> a -> c
. StackIndex -> Peek e Text
forall e. Peeker e Text
peekText
          peekArray :: Peek e Value
peekArray = Array -> Value
Aeson.Array (Array -> Value) -> ([Value] -> Array) -> [Value] -> Value
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [Value] -> Array
forall a. [a] -> Vector a
Vector.fromList ([Value] -> Value) -> Peek e [Value] -> Peek e Value
forall (m :: * -> *) a b. Monad m => (a -> b) -> m a -> m b
<$!>
            (Name -> Peek e [Value] -> Peek e [Value]
forall e a. Name -> Peek e a -> Peek e a
retrieving Name
"vector" (Peek e [Value] -> Peek e [Value])
-> Peek e [Value] -> Peek e [Value]
forall a b. (a -> b) -> a -> b
$! Peeker e Value -> Peeker e [Value]
forall a e. LuaError e => Peeker e a -> Peeker e [a]
peekList Peeker e Value
forall e. LuaError e => Peeker e Value
peekValue StackIndex
idx)
          isarray :: LuaE e Bool
isarray = StackIndex -> LuaE e Bool
forall e. StackIndex -> LuaE e Bool
getmetatable StackIndex
idx LuaE e Bool -> (Bool -> LuaE e Bool) -> LuaE e Bool
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
            Bool
False ->
              -- check for nonempty sequence
              (Type -> Type -> Bool
forall a. Eq a => a -> a -> Bool
/= Type
TypeNil) (Type -> Bool) -> LuaE e Type -> LuaE e Bool
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> StackIndex -> Integer -> LuaE e Type
forall e. LuaError e => StackIndex -> Integer -> LuaE e Type
rawgeti StackIndex
idx Integer
1 LuaE e Bool -> LuaE e () -> LuaE e Bool
forall (f :: * -> *) a b. Applicative f => f a -> f b -> f a
<* Int -> LuaE e ()
forall e. Int -> LuaE e ()
pop Int
1
            Bool
True  -> Name -> LuaE e Type
forall e. Name -> LuaE e Type
getmetatable' Name
jsonarray LuaE e Type -> (Type -> LuaE e Bool) -> LuaE e Bool
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
              Type
TypeTable -> StackIndex -> StackIndex -> LuaE e Bool
forall e. StackIndex -> StackIndex -> LuaE e Bool
rawequal (CInt -> StackIndex
nth CInt
1) (CInt -> StackIndex
nth CInt
2) LuaE e Bool -> LuaE e () -> LuaE e Bool
forall (f :: * -> *) a b. Applicative f => f a -> f b -> f a
<* Int -> LuaE e ()
forall e. Int -> LuaE e ()
pop Int
2
              Type
_         -> Bool -> LuaE e Bool
forall (f :: * -> *) a. Applicative f => a -> f a
pure Bool
False
      LuaE e Bool -> Peek e Bool
forall e a. LuaE e a -> Peek e a
liftLua LuaE e Bool
isarray Peek e Bool -> (Bool -> Peek e Value) -> Peek e Value
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= \case
        Bool
True  -> Peek e Value
peekArray
        Bool
False -> Object -> Value
Aeson.Object (Object -> Value)
-> ([(Key, Value)] -> Object) -> [(Key, Value)] -> Value
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [(Key, Value)] -> Object
forall v. [(Key, v)] -> KeyMap v
KeyMap.fromList ([(Key, Value)] -> Value) -> Peek e [(Key, Value)] -> Peek e Value
forall (m :: * -> *) a b. Monad m => (a -> b) -> m a -> m b
<$!>
                 Peeker e Key -> Peeker e Value -> Peeker e [(Key, Value)]
forall e a b.
LuaError e =>
Peeker e a -> Peeker e b -> Peeker e [(a, b)]
peekKeyValuePairs Peeker e Key
forall e. StackIndex -> Peek e Key
peekKey Peeker e Value
forall e. LuaError e => Peeker e Value
peekValue StackIndex
idx
  Type
luaType -> String -> Peek e Value
forall (m :: * -> *) a. MonadFail m => String -> m a
fail (String
"Unexpected type: " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Type -> String
forall a. Show a => a -> String
show Type
luaType)

-- | Retrieves a value from the Lua stack via JSON.
peekViaJSON :: (Aeson.FromJSON a, LuaError e) => Peeker e a
peekViaJSON :: Peeker e a
peekViaJSON StackIndex
idx = do
  Value
value <- Peeker e Value
forall e. LuaError e => Peeker e Value
peekValue StackIndex
idx
  case Value -> Result a
forall a. FromJSON a => Value -> Result a
Aeson.fromJSON Value
value of
    Aeson.Success a
x -> a -> Peek e a
forall (f :: * -> *) a. Applicative f => a -> f a
pure a
x
    Aeson.Error String
msg -> ByteString -> Peek e a
forall a e. ByteString -> Peek e a
failPeek (ByteString -> Peek e a) -> ByteString -> Peek e a
forall a b. (a -> b) -> a -> b
$ ByteString
"failed to decode: " ByteString -> ByteString -> ByteString
`B.append`
                       String -> ByteString
UTF8.fromString String
msg

-- | Pushes a value to the Lua stack as a JSON-like value.
pushViaJSON :: (Aeson.ToJSON a, LuaError e) => Pusher e a
pushViaJSON :: Pusher e a
pushViaJSON = Pusher e Value
forall e. LuaError e => Pusher e Value
pushValue Pusher e Value -> (a -> Value) -> Pusher e a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> Value
forall a. ToJSON a => a -> Value
Aeson.toJSON