106 lines
3.1 KiB
Haskell
106 lines
3.1 KiB
Haskell
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{- This Source Code Form is subject to the terms of the Mozilla Public License,
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v. 2.0. If a copy of the MPL was not distributed with this file, You can
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obtain one at https://mozilla.org/MPL/2.0/. -}
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{-# LANGUAGE OverloadedStrings #-}
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-- | ToGraphQL and FromGraphQL typeclasses used for user-defined type
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-- conversion.
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module Language.GraphQL.Class
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( FromGraphQL(..)
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, ToGraphQL(..)
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) where
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import Data.Foldable (toList)
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import Data.Int (Int8, Int16, Int32, Int64)
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import Data.Text (Text)
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import qualified Data.Text.Read as Text.Read
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import Data.Vector (Vector)
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import qualified Data.Vector as Vector
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import qualified Language.GraphQL.Type as Type
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fromGraphQLToIntegral :: Integral a => Type.Value -> Maybe a
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fromGraphQLToIntegral (Type.Int value) = Just $ fromIntegral value
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fromGraphQLToIntegral (Type.String value) =
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case Text.Read.decimal value of
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Right (converted, "") -> Just converted
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_ -> Nothing
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fromGraphQLToIntegral _ = Nothing
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-- | Instances of this typeclass can be converted to GraphQL internal
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-- representation.
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class ToGraphQL a where
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toGraphQL :: a -> Type.Value
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instance ToGraphQL Text where
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toGraphQL = Type.String
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instance ToGraphQL Int where
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toGraphQL = Type.Int . fromIntegral
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instance ToGraphQL Int8 where
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toGraphQL = Type.Int . fromIntegral
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instance ToGraphQL Int16 where
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toGraphQL = Type.Int . fromIntegral
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instance ToGraphQL Int32 where
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toGraphQL = Type.Int
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instance ToGraphQL Int64 where
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toGraphQL = Type.Int . fromIntegral
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instance ToGraphQL a => ToGraphQL [a] where
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toGraphQL = Type.List . fmap toGraphQL
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instance ToGraphQL a => ToGraphQL (Vector a) where
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toGraphQL = Type.List . toList . fmap toGraphQL
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instance ToGraphQL a => ToGraphQL (Maybe a) where
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toGraphQL (Just justValue) = toGraphQL justValue
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toGraphQL Nothing = Type.Null
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instance ToGraphQL Bool where
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toGraphQL = Type.Boolean
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-- | Instances of this typeclass can be used to convert GraphQL internal
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-- representation to user-defined type.
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class FromGraphQL a where
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fromGraphQL :: Type.Value -> Maybe a
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instance FromGraphQL Text where
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fromGraphQL (Type.String value) = Just value
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fromGraphQL _ = Nothing
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instance FromGraphQL Int where
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fromGraphQL = fromGraphQLToIntegral
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instance FromGraphQL Int8 where
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fromGraphQL = fromGraphQLToIntegral
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instance FromGraphQL Int16 where
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fromGraphQL = fromGraphQLToIntegral
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instance FromGraphQL Int32 where
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fromGraphQL = fromGraphQLToIntegral
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instance FromGraphQL Int64 where
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fromGraphQL = fromGraphQLToIntegral
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instance FromGraphQL a => FromGraphQL [a] where
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fromGraphQL (Type.List value) = traverse fromGraphQL value
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fromGraphQL _ = Nothing
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instance FromGraphQL a => FromGraphQL (Vector a) where
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fromGraphQL (Type.List value) = Vector.fromList
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<$> traverse fromGraphQL value
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fromGraphQL _ = Nothing
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instance FromGraphQL a => FromGraphQL (Maybe a) where
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fromGraphQL Type.Null = Just Nothing
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fromGraphQL value = Just <$> fromGraphQL value
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instance FromGraphQL Bool where
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fromGraphQL (Type.Boolean value) = Just value
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fromGraphQL _ = Nothing
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