1 files changed, 66 insertions, 10 deletions
diff --git a/Data/GraphQL/Schema.hs b/Data/GraphQL/Schema.hs
index 4ec3748..510741b 100644
--- a/Data/GraphQL/Schema.hs
+++ b/Data/GraphQL/Schema.hs
@@ -1,20 +1,46 @@
 {-# LANGUAGE CPP #-}
-module Data.GraphQL.Schema where
+module Data.GraphQL.Schema
+  ( Schema(..)
+  , QueryRoot
+  , ResolverO
+  , ResolverM
+  , Output(..)
+  , Subs
+  , Scalar(..)
+  , withField
+  , withFieldFinal
+  , withFields
+  , withArgument
+  , outputTraverse
+  , fields
+  -- * Reexports
+  , Field
+  , Argument
+  ) where
 
 #if !MIN_VERSION_base(4,8,0)
-import Control.Applicative ((<$>))
+import Data.Traversable (traverse)
 #endif
+import Control.Applicative
+import Data.Maybe (catMaybes)
+import Data.Foldable (fold)
 import Data.String (IsString(fromString))
 
 import Data.Aeson (ToJSON(toJSON))
 import Data.HashMap.Strict (HashMap)
+import qualified Data.HashMap.Strict as HashMap
 import Data.Text (Text, pack)
+import qualified Data.Text as T (null)
+
+import Data.GraphQL.AST
 
 data Schema f = Schema (QueryRoot f)
 
-type QueryRoot f = Resolver f
+type QueryRoot f = ResolverM f
 
-type Resolver f = Input -> f Output
+-- TODO: Come up with a unique data type or better renaming
+type ResolverM f =  Field  -> f (HashMap Text Output)
+type ResolverO f = [Field] -> f Output
 
 data Output = OutputObject (HashMap Text Output)
             | OutputList [Output]
@@ -22,12 +48,7 @@ data Output = OutputObject (HashMap Text Output)
             | OutputEnum Text
               deriving (Show)
 
-type Argument = (Text, Scalar)
-
-type Subs = Text -> Maybe Scalar
-
-data Input = InputField Text [Argument] [Input]
-             deriving (Show)
+type Subs = Text -> Maybe Text
 
 -- TODO: GraphQL spec for Integer Scalar is 32bits
 data Scalar = ScalarInt     Int
@@ -53,3 +74,38 @@ instance ToJSON Output where
     toJSON (OutputScalar x) = toJSON x
     toJSON (OutputEnum   x) = toJSON x
 
+-- * Helpers
+
+withField :: Alternative f => Text -> ([Argument] -> ResolverO f) -> ResolverM f
+withField n f (Field alias name' args _ sels) =
+  if n == name'
+     then HashMap.singleton aliasOrName <$> f args (fields sels)
+     else empty
+  where
+    aliasOrName = if T.null alias then name' else alias
+
+withFieldFinal :: Alternative f => Text -> Output -> ResolverM f
+withFieldFinal n o fld@(Field _ _ [] _ []) = withField n (\_ _ -> pure o) fld
+withFieldFinal _ _ _ = empty
+
+withFields :: Alternative f => ResolverM f -> ResolverO f
+withFields f = fmap (OutputObject . fold) . traverse f
+
+outputTraverse :: Applicative f => (a -> f Output) -> [a] -> f Output
+outputTraverse f = fmap OutputList . traverse f
+
+withArgument :: Text -> [Argument] -> Maybe Scalar
+withArgument x [Argument n s] = if x == n then scalarValue s else Nothing
+withArgument _ _ = Nothing
+
+scalarValue :: Value -> Maybe Scalar
+scalarValue (ValueInt x) = Just . ScalarInt $ fromIntegral x
+scalarValue (ValueString (StringValue x)) = Just $ ScalarString x
+scalarValue _ = Nothing
+
+fields :: SelectionSet -> [Field]
+fields = catMaybes . fmap field
+
+field :: Selection -> Maybe Field
+field (SelectionField x) = Just x
+field _ = Nothing