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{-# LANGUAGE CPP #-}
{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE LambdaCase #-}
module Data.GraphQL.Execute where
#if !MIN_VERSION_base(4,8,0)
import Control.Applicative (Applicative, (<$>), pure)
#endif
import Control.Applicative (Alternative, empty)
import qualified Data.Aeson as Aeson
import Data.GraphQL.AST
import Data.GraphQL.Schema
type Response = Aeson.Value
execute :: (Alternative f, Monad f) => Schema f -> Document -> f Response
execute (Schema resolv0) doc = go resolv0 =<< root doc
where
root :: Applicative f => Document -> f Selection
root (Document [DefinitionOperation (Query (Node _ _ _ [sel]))]) = pure sel
root _ = error "root: Not implemented yet"
go :: (Alternative f, Monad f) => Resolver f -> Selection -> f Response
go resolv (SelectionField (Field _ n _ _ sfs)) =
resolv (InputField n) >>= \case
(OutputScalar s) ->
if null sfs
then (\s' -> Aeson.Object [(n, Aeson.toJSON s')]) <$> s
else empty
(OutputResolver resolv') -> (\r-> Aeson.Object [(n, r)]) <$> go resolv' (head sfs)
_ -> error "go case resolv: Not implemented yet"
go _ _ = error "go: Not implemented yet"
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