Add JSON Serialize instance

src/Language/GraphQL/Serialize.hs

@@ -1,7 +1,43 @@
+{-# LANGUAGE OverloadedStrings #-}
+
 module Language.GraphQL.Serialize
     ( JSON(..)
     ) where
 
 import qualified Data.Aeson as Aeson
+import qualified Data.Aeson.Key as Aeson.Key
+import Language.GraphQL.Execute.Coerce
+import qualified Language.GraphQL.Execute.OrderedMap as OrderedMap
+import qualified Language.GraphQL.Type.Out as Out
+import qualified Language.GraphQL.Type as Type
 
 newtype JSON = JSON Aeson.Value
+
+instance Aeson.ToJSON JSON where
+    toJSON (JSON value) = value
+
+instance Aeson.FromJSON JSON where
+    parseJSON = pure . JSON
+
+instance Serialize JSON where
+    serialize (Out.ScalarBaseType scalarType) value
+        | Type.ScalarType "Int" _ <- scalarType
+        , Int int <- value = Just $ JSON $ Aeson.Number $ fromIntegral int
+        | Type.ScalarType "Float" _ <- scalarType
+        , Float float <- value = Just $ JSON $ Aeson.toJSON float
+        | Type.ScalarType "String" _ <- scalarType
+        , String string <- value = Just $ JSON $ Aeson.String string
+        | Type.ScalarType "ID" _ <- scalarType
+        , String string <- value = Just $ JSON $ Aeson.String string
+        | Type.ScalarType "Boolean" _ <- scalarType
+        , Boolean boolean <- value = Just $ JSON $ Aeson.Bool boolean
+    serialize _ (Enum enum) = Just $ JSON $ Aeson.String enum
+    serialize _ (List list) = Just $ JSON $ Aeson.toJSON list
+    serialize _ (Object object) = Just
+        $ JSON
+        $ Aeson.object
+        $ toJSONKeyValue <$> OrderedMap.toList object
+      where
+        toJSONKeyValue (key, value) = (Aeson.Key.fromText key, Aeson.toJSON value)
+    serialize _ _ = Nothing
+    null = JSON Aeson.Null