module Data.GraphQL.Schema where

import Data.Maybe (catMaybes)
import Text.Show.Functions ()

import Data.Text (Text)
import Data.Aeson (ToJSON(toJSON))

-- TODO: Support side-effects

data Schema = Schema QueryRoot -- (Maybe  MutationRoot)

type QueryRoot = Resolver

type Resolver = Input -> Output

data Output = OutputResolver Resolver
            | OutputList [Output]
            | OutputScalar Scalar
         -- | OutputUnion [Output]
         -- | OutputEnum [Scalar]
         -- | OutputNonNull (Output)
            | OutputError
              deriving (Show)

data Input = InputScalar Scalar
           | InputField Text
           | InputList [Input]
             deriving (Show)

field :: Input -> Maybe Text
field (InputField x) = Just x
field _ = Nothing

fields :: [Input] -> [Text]
fields = catMaybes . fmap field

data Scalar = ScalarInt     Int
            | ScalarFloat   Double
            | ScalarString  Text
            | ScalarBoolean Bool
            | ScalarID      Text
              deriving (Show)

instance ToJSON Scalar where
    toJSON (ScalarInt     x) = toJSON x
    toJSON (ScalarFloat   x) = toJSON x
    toJSON (ScalarString  x) = toJSON x
    toJSON (ScalarBoolean x) = toJSON x
    toJSON (ScalarID      x) = toJSON x