Handle Field arguments in Schema definition

The `Schema` has been overhauled to make `Output` monomorphic.
Traversing the `GraphQL` document is handled implicitly while defining
the `Schema`.

The 4th end-to-end test from `graphql-js` has been ported.

Data/GraphQL/Execute.hs

@@ -3,7 +3,7 @@
 module Data.GraphQL.Execute where
 
 #if !MIN_VERSION_base(4,8,0)
-import Control.Applicative (Applicative, (<$>), pure)
+import Control.Applicative ((<$>), pure)
 import Data.Traversable (traverse)
 #endif
 import Control.Applicative (Alternative, empty)
@@ -13,32 +13,35 @@ import qualified Data.Aeson as Aeson
 import qualified Data.HashMap.Strict as HashMap
 
 import Data.GraphQL.AST
-import Data.GraphQL.Schema
+import Data.GraphQL.Schema (Resolver, Schema(..))
+import qualified Data.GraphQL.Schema as Schema
 
-execute :: (Alternative f, Monad f) => Schema f -> Document -> f Aeson.Value
+execute :: (Alternative m, Monad m) => Schema m -> Document -> m Aeson.Value
 execute (Schema resolv) doc = selectionSet resolv =<< query doc
 
-query :: Applicative f => Document -> f SelectionSet
+query :: Alternative f => Document -> f SelectionSet
 query (Document [DefinitionOperation (Query (Node _ _ _ sels))]) = pure sels
-query _ = error "query: Not implemented yet"
+query _ = empty
 
-selectionSet :: (Alternative f, Monad f) => Resolver f -> SelectionSet -> f Aeson.Value
-selectionSet resolv sels = Aeson.Object . fold <$> traverse (selection resolv) sels
+selectionSet :: Alternative f => Resolver f -> SelectionSet -> f Aeson.Value
+selectionSet resolv = fmap (Aeson.Object . fold) . traverse (selection resolv)
 
-selection :: (Alternative f, Monad f) => Resolver f -> Selection -> f Aeson.Object
-selection resolv (SelectionField (Field _ n _ _ sfs)) =
-    fmap (HashMap.singleton n) $ output sfs =<< resolv (InputField n)
-selection _ _ = error "selection: Not implemented yet"
+selection :: Alternative f => Resolver f -> Selection -> f Aeson.Object
+selection resolv (SelectionField field@(Field _ name _ _ _)) =
+    fmap (HashMap.singleton name) $ Aeson.toJSON <$> resolv (fieldToInput field)
+selection _ _ = empty
 
-output :: (Alternative f, Monad f) => SelectionSet -> Output f -> f Aeson.Value
-output sels (OutputResolver resolv) = selectionSet resolv sels
-output sels (OutputList os) = fmap array . traverse (output sels) =<< os
-output sels (OutputEnum e)
-   | null sels = Aeson.toJSON <$> e
-   | otherwise = empty
-output sels (OutputScalar s)
-   | null sels = Aeson.toJSON <$> s
-   | otherwise = empty
+-- * AST/Schema conversions
 
-array :: [Aeson.Value] -> Aeson.Value
-array = Aeson.toJSON
+argument :: Argument -> Schema.Argument
+argument (Argument n (ValueInt v)) = (n, Schema.ScalarInt $ fromIntegral v)
+argument (Argument n (ValueString (StringValue v))) = (n, Schema.ScalarString v)
+argument _ = error "argument: not implemented yet"
+
+fieldToInput :: Field -> Schema.Input
+fieldToInput (Field _ n as _ sels) =
+  Schema.InputField n (argument <$> as) (fieldToInput . selectionToField <$> sels)
+
+selectionToField :: Selection -> Field
+selectionToField (SelectionField x) = x
+selectionToField _ = error "selectionField: not implemented yet"

Data/GraphQL/Schema.hs

@@ -1,35 +1,34 @@
+{-# LANGUAGE CPP #-}
 module Data.GraphQL.Schema where
 
-import Data.Maybe (catMaybes)
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative ((<$>))
+#endif
 
-import Data.Text (Text)
 import Data.Aeson (ToJSON(toJSON))
+import Data.HashMap.Strict (HashMap)
+import Data.Text (Text)
 
 data Schema f = Schema (QueryRoot f) -- (Maybe  MutationRoot)
 
 type QueryRoot f = Resolver f
 
-type Resolver f = Input -> f (Output f)
+type Resolver f = Input -> f Output
 
-data Output f = OutputResolver (Resolver f)
-              | OutputList (f [Output f])
-              | OutputScalar (f Scalar)
-              | OutputEnum (f Text)
+data Output = OutputObject (HashMap Text Output)
+            | OutputList [Output]
+            | OutputScalar Scalar
+            | OutputEnum Text
+              deriving (Show)
            -- | OutputUnion [Output]
            -- | OutputNonNull (Output)
 
-data Input = InputScalar Scalar
-           | InputField Text
-           | InputList [Input]
+type Argument = (Text, Scalar)
+
+data Input = InputField Text [Argument] [Input]
              deriving (Show)
 
-field :: Input -> Maybe Text
-field (InputField x) = Just x
-field _ = Nothing
-
-fields :: [Input] -> [Text]
-fields = catMaybes . fmap field
-
+-- TODO: Make ScalarInt Int32
 data Scalar = ScalarInt     Int
             | ScalarFloat   Double
             | ScalarString  Text
@@ -43,3 +42,10 @@ instance ToJSON Scalar where
     toJSON (ScalarString  x) = toJSON x
     toJSON (ScalarBoolean x) = toJSON x
     toJSON (ScalarID      x) = toJSON x
+
+instance ToJSON Output where
+    toJSON (OutputObject x) = toJSON $ toJSON <$> x
+    toJSON (OutputList   x) = toJSON $ toJSON <$> x
+    toJSON (OutputScalar x) = toJSON x
+    toJSON (OutputEnum   x) = toJSON x
+