{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}

module Json.Path
  ( Path (..)

    -- * Encoding
  , encode
  , builderUtf8

    -- * Lookup
  , query
  , query'

    -- * Reverse
  , reverse
  ) where

import Prelude hiding (reverse)

import Data.ByteString.Short.Internal (ShortByteString (SBS))
import Data.Bytes.Builder (Builder)
import Data.Primitive (ByteArray (ByteArray))
import Data.Text.Short (ShortText)
import Json (Member (Member), Value (Array, Null, Object))

import qualified Data.Bytes.Builder as Builder
import qualified Data.Bytes.Chunks as ByteChunks
import qualified Data.Primitive as PM
import qualified Data.Text.Short.Unsafe as TS

-- | A path to an object.
data Path
  = -- | JSON path element of a key into an object, \"object.key\".
    Key {-# UNPACK #-} !ShortText !Path
  | -- | JSON path element of an index into an array, \"array[index]\".
    -- Negative numbers result in undefined behavior.
    Index {-# UNPACK #-} !Int !Path
  | Nil
  deriving (Path -> Path -> Bool
(Path -> Path -> Bool) -> (Path -> Path -> Bool) -> Eq Path
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: Path -> Path -> Bool
== :: Path -> Path -> Bool
$c/= :: Path -> Path -> Bool
/= :: Path -> Path -> Bool
Eq, Int -> Path -> ShowS
[Path] -> ShowS
Path -> String
(Int -> Path -> ShowS)
-> (Path -> String) -> ([Path] -> ShowS) -> Show Path
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> Path -> ShowS
showsPrec :: Int -> Path -> ShowS
$cshow :: Path -> String
show :: Path -> String
$cshowList :: [Path] -> ShowS
showList :: [Path] -> ShowS
Show)

{- | Encode a path.

>>> encode (Key "foo" $ Index 5 $ Key "bar" $ Nil)
-}
encode :: Path -> ShortText
encode :: Path -> ShortText
encode Path
p = ByteArray -> ShortText
ba2st (Chunks -> ByteArray
ByteChunks.concatU (Int -> Builder -> Chunks
Builder.run Int
128 (Path -> Builder
builderUtf8 Path
p)))

builderUtf8 :: Path -> Builder
builderUtf8 :: Path -> Builder
builderUtf8 Path
p0 = Char -> Builder
Builder.ascii Char
'$' Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> Path -> Builder
go Path
p0
 where
  go :: Path -> Builder
go Path
Nil = Builder
forall a. Monoid a => a
mempty
  go (Key ShortText
k Path
p) = Char -> Builder
Builder.ascii Char
'.' Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> ShortText -> Builder
Builder.shortTextUtf8 ShortText
k Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> Path -> Builder
go Path
p
  go (Index Int
i Path
p) =
    Char -> Builder
Builder.ascii Char
'['
      Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> Word -> Builder
Builder.wordDec (Int -> Word
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int
i)
      Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> Char -> Builder
Builder.ascii Char
']'
      Builder -> Builder -> Builder
forall a. Semigroup a => a -> a -> a
<> Path -> Builder
go Path
p

{- | Search for an element at the given path. Returns 'Nothing' if
anything in the path is missing.
-}
query :: Path -> Value -> Maybe Value
query :: Path -> Value -> Maybe Value
query = Path -> Value -> Maybe Value
go
 where
  go :: Path -> Value -> Maybe Value
go Path
Nil Value
v = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
v
  go (Key ShortText
k Path
p) (Object SmallArray Member
mbrs) =
    (Member -> Maybe Value -> Maybe Value)
-> Maybe Value -> SmallArray Member -> Maybe Value
forall a b. (a -> b -> b) -> b -> SmallArray a -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr
      ( \(Member ShortText
key Value
val) Maybe Value
other ->
          if ShortText
key ShortText -> ShortText -> Bool
forall a. Eq a => a -> a -> Bool
== ShortText
k
            then Value -> Maybe Value
forall a. a -> Maybe a
Just Value
val
            else Maybe Value
other
      )
      Maybe Value
forall a. Maybe a
Nothing
      SmallArray Member
mbrs
      Maybe Value -> (Value -> Maybe Value) -> Maybe Value
forall a b. Maybe a -> (a -> Maybe b) -> Maybe b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= Path -> Value -> Maybe Value
go Path
p
  go (Index Int
i Path
p) (Array SmallArray Value
vs) =
    if Int
i Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< SmallArray Value -> Int
forall a. SmallArray a -> Int
PM.sizeofSmallArray SmallArray Value
vs
      then
        let !(# Value
e #) = SmallArray Value -> Int -> (# Value #)
forall a. SmallArray a -> Int -> (# a #)
PM.indexSmallArray## SmallArray Value
vs Int
i
         in Path -> Value -> Maybe Value
go Path
p Value
e
      else Maybe Value
forall a. Maybe a
Nothing
  go Path
_ Value
_ = Maybe Value
forall a. Maybe a
Nothing

{- | Variant of 'query' that returns 'Null' if anything in the path
is missing.
-}
query' :: Path -> Value -> Value
query' :: Path -> Value -> Value
query' = Path -> Value -> Value
go
 where
  go :: Path -> Value -> Value
go Path
Nil Value
v = Value
v
  go (Key ShortText
k Path
p) (Object SmallArray Member
mbrs) =
    Path -> Value -> Value
go Path
p (Value -> Value) -> Value -> Value
forall a b. (a -> b) -> a -> b
$
      (Member -> Value -> Value) -> Value -> SmallArray Member -> Value
forall a b. (a -> b -> b) -> b -> SmallArray a -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr
        ( \(Member ShortText
key Value
val) Value
other ->
            if ShortText
key ShortText -> ShortText -> Bool
forall a. Eq a => a -> a -> Bool
== ShortText
k
              then Value
val
              else Value
other
        )
        Value
Null
        SmallArray Member
mbrs
  go (Index Int
i Path
p) (Array SmallArray Value
vs) =
    if Int
i Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< SmallArray Value -> Int
forall a. SmallArray a -> Int
PM.sizeofSmallArray SmallArray Value
vs
      then
        let !(# Value
e #) = SmallArray Value -> Int -> (# Value #)
forall a. SmallArray a -> Int -> (# a #)
PM.indexSmallArray## SmallArray Value
vs Int
i
         in Path -> Value -> Value
go Path
p Value
e
      else Value
Null
  go Path
_ Value
_ = Value
Null

ba2st :: ByteArray -> ShortText
ba2st :: ByteArray -> ShortText
ba2st (ByteArray ByteArray#
x) = ShortByteString -> ShortText
TS.fromShortByteStringUnsafe (ByteArray# -> ShortByteString
SBS ByteArray#
x)

reverse :: Path -> Path
reverse :: Path -> Path
reverse = Path -> Path -> Path
go Path
Nil
 where
  go :: Path -> Path -> Path
go !Path
acc Path
Nil = Path
acc
  go !Path
acc (Key ShortText
k Path
xs) = Path -> Path -> Path
go (ShortText -> Path -> Path
Key ShortText
k Path
acc) Path
xs
  go !Path
acc (Index Int
i Path
xs) = Path -> Path -> Path
go (Int -> Path -> Path
Index Int
i Path
acc) Path
xs