1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
|
{-# LANGUAGE ExplicitForAll #-}
{-# LANGUAGE TupleSections #-}
-- | After the document is parsed, before getting executed the AST is
-- transformed into a similar, simpler AST. This module is responsible for
-- this transformation.
module Language.GraphQL.Execute.Transform
( document
) where
import Control.Arrow (first)
import Control.Monad (foldM, unless)
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.Reader (ReaderT, ask, runReaderT)
import Control.Monad.Trans.State (StateT, evalStateT, gets, modify)
import Data.HashMap.Strict (HashMap)
import qualified Data.HashMap.Strict as HashMap
import qualified Data.List.NonEmpty as NonEmpty
import Data.Sequence (Seq, (<|), (><))
import qualified Language.GraphQL.AST as Full
import qualified Language.GraphQL.AST.Core as Core
import Language.GraphQL.AST.Document (Definition(..), Document)
import qualified Language.GraphQL.Schema as Schema
import qualified Language.GraphQL.Type.Directive as Directive
-- | Associates a fragment name with a list of 'Core.Field's.
data Replacement = Replacement
{ fragments :: HashMap Core.Name Core.Fragment
, fragmentDefinitions :: HashMap Full.Name Full.FragmentDefinition
}
type TransformT a = StateT Replacement (ReaderT Schema.Subs Maybe) a
liftJust :: forall a. a -> TransformT a
liftJust = lift . lift . Just
-- | Rewrites the original syntax tree into an intermediate representation used
-- for query execution.
document :: Schema.Subs -> Document -> Maybe Core.Document
document subs document' =
flip runReaderT subs
$ evalStateT (collectFragments >> operations operationDefinitions)
$ Replacement HashMap.empty fragmentTable
where
(fragmentTable, operationDefinitions) = foldr defragment mempty document'
defragment (ExecutableDefinition (Full.DefinitionOperation definition)) acc =
(definition :) <$> acc
defragment (ExecutableDefinition (Full.DefinitionFragment definition)) acc =
let (Full.FragmentDefinition name _ _ _) = definition
in first (HashMap.insert name definition) acc
defragment _ acc = acc
-- * Operation
operations :: [Full.OperationDefinition] -> TransformT Core.Document
operations operations' = do
coreOperations <- traverse operation operations'
lift . lift $ NonEmpty.nonEmpty coreOperations
operation :: Full.OperationDefinition -> TransformT Core.Operation
operation (Full.SelectionSet sels)
= operation $ Full.OperationDefinition Full.Query mempty mempty mempty sels
-- TODO: Validate Variable definitions with substituter
operation (Full.OperationDefinition Full.Query name _vars _dirs sels)
= Core.Query name <$> appendSelection sels
operation (Full.OperationDefinition Full.Mutation name _vars _dirs sels)
= Core.Mutation name <$> appendSelection sels
-- * Selection
selection ::
Full.Selection ->
TransformT (Either (Seq Core.Selection) Core.Selection)
selection (Full.Field alias name arguments' directives' selections) =
maybe (Left mempty) (Right . Core.SelectionField) <$> do
fieldArguments <- traverse argument arguments'
fieldSelections <- appendSelection selections
fieldDirectives <- Directive.selection <$> directives directives'
let field' = Core.Field alias name fieldArguments fieldSelections
pure $ field' <$ fieldDirectives
selection (Full.FragmentSpread name directives') =
maybe (Left mempty) (Right . Core.SelectionFragment) <$> do
spreadDirectives <- Directive.selection <$> directives directives'
fragments' <- gets fragments
fragment <- maybe lookupDefinition liftJust (HashMap.lookup name fragments')
pure $ fragment <$ spreadDirectives
where
lookupDefinition = do
fragmentDefinitions' <- gets fragmentDefinitions
found <- lift . lift $ HashMap.lookup name fragmentDefinitions'
fragmentDefinition found
selection (Full.InlineFragment type' directives' selections) = do
fragmentDirectives <- Directive.selection <$> directives directives'
case fragmentDirectives of
Nothing -> pure $ Left mempty
_ -> do
fragmentSelectionSet <- appendSelection selections
pure $ maybe Left selectionFragment type' fragmentSelectionSet
where
selectionFragment typeName = Right
. Core.SelectionFragment
. Core.Fragment typeName
appendSelection ::
Traversable t =>
t Full.Selection ->
TransformT (Seq Core.Selection)
appendSelection = foldM go mempty
where
go acc sel = append acc <$> selection sel
append acc (Left list) = list >< acc
append acc (Right one) = one <| acc
directives :: [Full.Directive] -> TransformT [Core.Directive]
directives = traverse directive
where
directive (Full.Directive directiveName directiveArguments) =
Core.Directive directiveName <$> arguments directiveArguments
-- * Fragment replacement
-- | Extract fragment definitions into a single 'HashMap'.
collectFragments :: TransformT ()
collectFragments = do
fragDefs <- gets fragmentDefinitions
let nextValue = head $ HashMap.elems fragDefs
unless (HashMap.null fragDefs) $ do
_ <- fragmentDefinition nextValue
collectFragments
fragmentDefinition ::
Full.FragmentDefinition ->
TransformT Core.Fragment
fragmentDefinition (Full.FragmentDefinition name type' _ selections) = do
modify deleteFragmentDefinition
fragmentSelection <- appendSelection selections
let newValue = Core.Fragment type' fragmentSelection
modify $ insertFragment newValue
liftJust newValue
where
deleteFragmentDefinition (Replacement fragments' fragmentDefinitions') =
Replacement fragments' $ HashMap.delete name fragmentDefinitions'
insertFragment newValue (Replacement fragments' fragmentDefinitions') =
let newFragments = HashMap.insert name newValue fragments'
in Replacement newFragments fragmentDefinitions'
arguments :: [Full.Argument] -> TransformT Core.Arguments
arguments = fmap Core.Arguments . foldM go HashMap.empty
where
go arguments' argument' = do
(Core.Argument name value') <- argument argument'
return $ HashMap.insert name value' arguments'
argument :: Full.Argument -> TransformT Core.Argument
argument (Full.Argument n v) = Core.Argument n <$> value v
value :: Full.Value -> TransformT Core.Value
value (Full.Variable n) = do
substitute' <- lift ask
lift . lift $ substitute' n
value (Full.Int i) = pure $ Core.Int i
value (Full.Float f) = pure $ Core.Float f
value (Full.String x) = pure $ Core.String x
value (Full.Boolean b) = pure $ Core.Boolean b
value Full.Null = pure Core.Null
value (Full.Enum e) = pure $ Core.Enum e
value (Full.List l) =
Core.List <$> traverse value l
value (Full.Object o) =
Core.Object . HashMap.fromList <$> traverse objectField o
objectField :: Full.ObjectField -> TransformT (Core.Name, Core.Value)
objectField (Full.ObjectField name value') = (name,) <$> value value'
|
