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{-# LANGUAGE OverloadedStrings #-}
-- | This module provides the function to execute a @GraphQL@ request --
-- according to a 'Schema'.
module Language.GraphQL.Execute
( execute
) where
import Control.Monad.IO.Class (MonadIO)
import qualified Data.List.NonEmpty as NE
import Data.List.NonEmpty (NonEmpty((:|)))
import qualified Data.Aeson as Aeson
import qualified Language.GraphQL.AST as AST
import qualified Language.GraphQL.AST.Core as AST.Core
import qualified Language.GraphQL.AST.Transform as Transform
import Language.GraphQL.Error
import Language.GraphQL.Schema (Schema)
import qualified Language.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
:: MonadIO m
=> Schema m -> Schema.Subs -> AST.Document -> m Aeson.Value
execute schema subs doc =
maybe transformError (document schema) $ Transform.document subs doc
where
transformError = return $ Aeson.object
[("errors", Aeson.toJSON
[ Aeson.object [("message", "Schema transformation error.")]
]
)]
document :: MonadIO m => Schema m -> AST.Core.Document -> m Aeson.Value
document schema (op :| []) = operation schema op
document _ _ = error "Multiple operations not supported yet"
operation :: MonadIO m => Schema m -> AST.Core.Operation -> m Aeson.Value
operation schema (AST.Core.Query flds)
= runCollectErrs (Schema.resolve (NE.toList schema) (NE.toList flds))
operation schema (AST.Core.Mutation flds)
= runCollectErrs (Schema.resolve (NE.toList schema) (NE.toList flds))
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