forked from OSS/graphql
52 lines
1.7 KiB
Haskell
52 lines
1.7 KiB
Haskell
{-# LANGUAGE CPP #-}
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{-# LANGUAGE OverloadedStrings #-}
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module Data.GraphQL.Execute (execute) where
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#if !MIN_VERSION_base(4,8,0)
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import Control.Applicative ((<$>))
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#endif
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import Control.Applicative (Alternative)
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import Data.Maybe (catMaybes)
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import qualified Data.Aeson as Aeson
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import Data.GraphQL.AST
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import Data.GraphQL.Schema (Schema(..))
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import qualified Data.GraphQL.Schema as Schema
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import Data.GraphQL.Error
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{- | Takes a schema, a substitution and a GraphQL document.
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The substition is applied to the document using rootFields, and
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the schema's resolvers are applied to the resulting fields.
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Returns the result of the query against the schema wrapped in a
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"data" field, or errors wrapped in a "errors field".
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-}
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execute :: Alternative m
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=> Schema.Schema m -> Schema.Subs -> Document -> m Aeson.Value
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execute (Schema resolvs) subs doc = runCollectErrs res
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where res = Schema.resolvers resolvs $ rootFields subs doc
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rootFields :: Schema.Subs -> Document -> [Field]
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rootFields subs (Document [DefinitionOperation (Query (Node _varDefs _ _ sels))]) =
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Schema.fields $ substitute subs <$> sels
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rootFields _ _ = []
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substitute :: Schema.Subs -> Selection -> Selection
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substitute subs (SelectionField (Field alias name args directives sels)) =
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SelectionField $ Field
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alias
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name
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-- TODO: Get rid of `catMaybes`, invalid arguments should raise an error
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(catMaybes $ subsArg subs <$> args)
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directives
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(substitute subs <$> sels)
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substitute _ sel = sel
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-- TODO: Support different value types
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subsArg :: Schema.Subs -> Argument -> Maybe Argument
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subsArg subs (Argument n (ValueVariable (Variable v))) =
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Argument n . ValueString <$> subs v
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subsArg _ arg = Just arg
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