module Data.Aeson.Encode.Pretty (encodePretty) where
import Data.Aeson (Value(..), ToJSON(..))
import qualified Data.Aeson.Encode as Aeson
import Data.ByteString.Lazy (ByteString)
import qualified Data.HashMap.Strict as H (toList)
import Data.List (intersperse)
import Data.Monoid (mappend, mconcat, mempty)
import Data.Text (Text)
import Data.Text.Lazy.Builder (Builder, toLazyText)
import Data.Text.Lazy.Encoding (encodeUtf8)
import qualified Data.Vector as V (toList)
type Indent = Int
encodePretty :: ToJSON a => a -> ByteString
encodePretty = encodeUtf8 . toLazyText . fromValue 0 . toJSON
fromValue :: Indent -> Value -> Builder
fromValue ind = go
where
go (Array v) = fromCompound ind ("[","]") fromValue (V.toList v)
go (Object m) = fromCompound ind ("{","}") fromPair (H.toList m)
go v = Aeson.fromValue v
fromCompound :: Indent
-> (Builder, Builder)
-> (Indent -> a -> Builder)
-> [a]
-> Builder
fromCompound ind (delimL,delimR) fromItem items =
delimL <>
if null items then mempty
else "\n" <> items' <> "\n" <> fromIndent ind <>
delimR
where
items' = mconcat . intersperse ",\n" $
map (\item -> fromIndent (ind+1) <> fromItem (ind+1) item)
items
fromPair :: Indent -> (Text, Value) -> Builder
fromPair ind (k,v) = Aeson.fromValue (toJSON k) <> ": " <> fromValue ind v
fromIndent :: Indent -> Builder
fromIndent ind = mconcat $ replicate (ind*4) " "
(<>) :: Builder -> Builder -> Builder
(<>) = mappend
infixr 6 <>