99 lines
3.5 KiB
Haskell
99 lines
3.5 KiB
Haskell
module Data.GraphQL.AST.Transform where
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import Control.Applicative (empty)
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import Control.Monad ((<=<))
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import Data.Bifunctor (first)
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import Data.Either (partitionEithers)
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import qualified Data.List.NonEmpty as NonEmpty
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import Data.Maybe (maybeToList)
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import Data.Monoid (Alt(Alt,getAlt))
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import Data.Foldable (foldMap)
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import Data.Text (Text)
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import qualified Data.GraphQL.AST as Full
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import qualified Data.GraphQL.AST.Core as Core
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import qualified Data.GraphQL.Schema as Schema
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type Name = Text
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-- | Replaces a fragment name by a list of 'Field'. If the name doesn't match an
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-- empty list is returned.
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type Fragmenter = Name -> [Core.Field]
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-- TODO: Replace Maybe by Either CustomError
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document :: Schema.Subs -> Full.Document -> Maybe Core.Document
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document subs defs = operations subs fr ops
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where
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(fr, ops) = first foldFrags . partitionEithers . NonEmpty.toList $ defrag <$> defs
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foldFrags :: [Fragmenter] -> Fragmenter
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foldFrags fs n = getAlt $ foldMap (Alt . ($ n)) fs
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-- * Operation
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operations
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:: Schema.Subs
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-> Fragmenter
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-> [Full.OperationDefinition]
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-> Maybe Core.Document
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operations subs fr = NonEmpty.nonEmpty <=< traverse (operation subs fr)
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operation
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:: Schema.Subs
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-> Fragmenter
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-> Full.OperationDefinition
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-> Maybe Core.Operation
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operation subs fr (Full.OperationSelectionSet sels) =
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operation subs fr $ Full.OperationDefinition Full.Query empty empty empty sels
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operation _subs fr (Full.OperationDefinition ot _n _vars _dirs sels) =
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case ot of
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Full.Query -> Core.Query <$> node
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Full.Mutation -> Core.Mutation <$> node
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where
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node = traverse (hush <=< selection fr) sels
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selection :: Fragmenter -> Full.Selection -> Maybe (Either [Core.Field] Core.Field)
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selection fr (Full.SelectionField _fld) = Right <$> field fr _fld
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selection fr (Full.SelectionFragmentSpread (Full.FragmentSpread n _dirs)) = Just . Left $ fr n
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selection _ (Full.SelectionInlineFragment _) = error "Inline fragments not supported yet"
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-- * Fragment replacement
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-- | Extract Fragments into a single Fragmenter function and a Operation
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-- Definition.
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defrag :: Full.Definition -> Either Fragmenter Full.OperationDefinition
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defrag (Full.DefinitionOperation op) = Right op
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defrag (Full.DefinitionFragment fragDef) = Left $ fragmentDefinition fragDef
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fragmentDefinition :: Full.FragmentDefinition -> Fragmenter
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fragmentDefinition (Full.FragmentDefinition name _tc _dirs sels) name' =
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-- TODO: Support fragments within fragments. Fold instead of map.
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if name == name'
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then either id pure =<< maybeToList =<< NonEmpty.toList (selection mempty <$> sels)
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else empty
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field :: Fragmenter -> Full.Field -> Maybe Core.Field
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field fr (Full.Field a n args _ sels) =
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Core.Field a n (argument <$> args) <$> traverse (hush <=< selection fr) sels
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argument :: Full.Argument -> Core.Argument
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argument (Full.Argument n v) = Core.Argument n (value v)
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value :: Full.Value -> Core.Value
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value (Full.ValueVariable _) = error "Variables within fragments not supported yet"
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value (Full.ValueInt i) = Core.ValueInt i
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value (Full.ValueFloat f) = Core.ValueFloat f
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value (Full.ValueString x) = Core.ValueString x
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value (Full.ValueBoolean b) = Core.ValueBoolean b
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value Full.ValueNull = Core.ValueNull
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value (Full.ValueEnum e) = Core.ValueEnum e
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value (Full.ValueList l) = Core.ValueList (value <$> l)
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value (Full.ValueObject o) = Core.ValueObject (objectField <$> o)
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objectField :: Full.ObjectField -> Core.ObjectField
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objectField (Full.ObjectField n v) = Core.ObjectField n (value v)
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hush :: Either a b -> Maybe b
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hush = either (const Nothing) Just
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