forked from OSS/graphql
72 lines
3.1 KiB
Haskell
72 lines
3.1 KiB
Haskell
{-# LANGUAGE OverloadedStrings #-}
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-- | This module provides the function to execute a @GraphQL@ request --
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-- according to a 'Schema'.
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module Data.GraphQL.Execute (execute) where
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import Control.Applicative (Alternative, empty)
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import qualified Data.List.NonEmpty as NE
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import Data.List.NonEmpty (NonEmpty((:|)))
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import qualified Data.Aeson as Aeson
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import qualified Data.HashMap.Strict as HashMap
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import qualified Data.GraphQL.AST as AST
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import qualified Data.GraphQL.AST.Core as AST.Core
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import qualified Data.GraphQL.AST.Transform as Transform
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import Data.GraphQL.Schema (Schema)
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import qualified Data.GraphQL.Schema as Schema
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-- | Takes a 'Schema', a variable substitution function ('Schema.Subs'), and a
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-- @GraphQL@ 'document'. The substitution is applied to the document using
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-- 'rootFields', and the 'Schema''s resolvers are applied to the resulting fields.
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--
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-- Returns the result of the query against the 'Schema' wrapped in a /data/ field, or
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-- errors wrapped in an /errors/ field.
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execute
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:: (Alternative f, Monad f)
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=> Schema f -> Schema.Subs -> AST.Document -> f Aeson.Value
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execute schema subs doc = document schema =<< maybe empty pure (Transform.document subs doc)
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document :: Alternative f => Schema f -> AST.Core.Document -> f Aeson.Value
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document schema (op :| []) = operation schema op
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document _ _ = error "Multiple operations not supported yet"
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operation :: Alternative f => Schema f -> AST.Core.Operation -> f Aeson.Value
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operation schema (AST.Core.Query flds) =
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Aeson.Object . HashMap.singleton "data"
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<$> Schema.resolve (NE.toList schema) (NE.toList flds)
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operation _ _ = error "Mutations not supported yet"
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-- | Takes a variable substitution function and a @GraphQL@ document.
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-- If the document contains one query (and no other definitions)
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-- it applies the substitution to the query's set of selections
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-- and then returns their fields.
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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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-- | Takes a variable substitution function and a selection. If the
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-- selection is a field it applies the substitution to the field's
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-- arguments using 'subsArg', and recursively applies the substitution to
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-- the arguments of fields nested in the primary field.
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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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-- | Takes a variable substitution function and an argument. If the
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-- argument's value is a variable the substitution is applied to the
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-- variable's name.
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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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