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{-# LANGUAGE CPP #-}
module Data.GraphQL.Execute (execute) where
#if !MIN_VERSION_base(4,8,0)
import Control.Applicative ((<$>), pure)
import Data.Traversable (traverse)
#endif
import Control.Applicative (Alternative, empty)
import Data.Foldable (fold)
import Data.Maybe (catMaybes)
import qualified Data.Aeson as Aeson
import qualified Data.HashMap.Strict as HashMap
import qualified Data.Text as T
import Data.GraphQL.AST
import Data.GraphQL.Schema (Resolver, Schema(..))
import qualified Data.GraphQL.Schema as Schema
execute
:: (Alternative m, Monad m)
=> Schema m -> Schema.Subs -> Document -> m Aeson.Value
execute (Schema resolv) f doc = selectionSet f resolv =<< query doc
query :: Alternative f => Document -> f SelectionSet
query (Document [DefinitionOperation (Query (Node _varDefs _ _ sels))]) = pure sels
query _ = empty
selectionSet
:: Alternative f
=> Schema.Subs -> Resolver f -> SelectionSet -> f Aeson.Value
selectionSet f resolv = fmap (Aeson.Object . fold)
. traverse (selection f resolv)
selection
:: Alternative f
=> Schema.Subs -> Resolver f -> Selection -> f Aeson.Object
selection f resolv (SelectionField field@(Field alias name _ _ _)) =
fmap (HashMap.singleton aliasOrName)
$ Aeson.toJSON
<$> resolv (fieldToInput f field)
where
aliasOrName = if T.null alias then name else alias
selection _ _ _ = empty
-- * AST/Schema conversions
argument :: Schema.Subs -> Argument -> Maybe Schema.Argument
argument f (Argument n (ValueVariable (Variable v))) =
maybe Nothing (\v' -> Just (n, v')) $ f v
argument _ (Argument n (ValueInt v)) =
Just (n, Schema.ScalarInt $ fromIntegral v)
argument _ (Argument n (ValueString (StringValue v))) =
Just (n, Schema.ScalarString v)
argument _ _ = error "argument: not implemented yet"
fieldToInput :: Schema.Subs -> Field -> Schema.Input
fieldToInput f (Field _ n as _ sels) =
-- TODO: Get rid of `catMaybes`, invalid arguments should raise an error
Schema.InputField n (catMaybes $ argument f <$> as)
(fieldToInput f . selectionToField <$> sels)
selectionToField :: Selection -> Field
selectionToField (SelectionField x) = x
selectionToField _ = error "selectionField: not implemented yet"
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