graphql/Data/GraphQL/Execute.hs

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{-# LANGUAGE OverloadedStrings #-}
-- | This module provides the function to execute a @GraphQL@ request --
-- according to a 'Schema'.
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module Data.GraphQL.Execute (execute) where
import Control.Applicative (Alternative, empty)
import qualified Data.List.NonEmpty as NE
import Data.List.NonEmpty (NonEmpty((:|)))
import qualified Data.Aeson as Aeson
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import qualified Data.HashMap.Strict as HashMap
import qualified Data.GraphQL.AST as AST
import qualified Data.GraphQL.AST.Core as AST.Core
import qualified Data.GraphQL.AST.Transform as Transform
import Data.GraphQL.Schema (Schema)
import qualified Data.GraphQL.Schema as Schema
-- | Takes a 'Schema', a variable substitution function ('Schema.Subs'), and a
-- @GraphQL@ 'document'. The substitution is applied to the document using
-- 'rootFields', and the 'Schema''s resolvers are applied to the resulting fields.
--
-- Returns the result of the query against the 'Schema' wrapped in a /data/ field, or
-- errors wrapped in an /errors/ field.
execute
:: (Alternative f, Monad f)
=> Schema f -> Schema.Subs -> AST.Document -> f Aeson.Value
execute schema subs doc = document schema =<< maybe empty pure (Transform.document subs doc)
document :: Alternative f => Schema f -> AST.Core.Document -> f Aeson.Value
document schema (op :| []) = operation schema op
document _ _ = error "Multiple operations not supported yet"
operation :: Alternative f => Schema f -> AST.Core.Operation -> f Aeson.Value
operation schema (AST.Core.Query flds) =
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Aeson.Object . HashMap.singleton "data"
<$> Schema.resolve (NE.toList schema) (NE.toList flds)
operation _ _ = error "Mutations not supported yet"