@@ -1,318 +1,312 @@
11{-# LANGUAGE CPP #-}
2+{-# LANGUAGE DeriveTraversable #-}
23{-# LANGUAGE FlexibleContexts #-}
4+{-# LANGUAGE FlexibleInstances #-}
5+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
36{-# LANGUAGE LambdaCase #-}
7+{-# LANGUAGE MultiParamTypeClasses #-}
48{-# LANGUAGE PatternGuards #-}
9+{-# LANGUAGE PatternSynonyms #-}
510{-# LANGUAGE ScopedTypeVariables #-}
611{-# LANGUAGE StandaloneDeriving #-}
12+{-# LANGUAGE TemplateHaskell #-}
13+{-# LANGUAGE TypeApplications #-}
714{-# LANGUAGE TypeFamilies #-}
8−{-# LANGUAGE UndecidableInstances #-}
15+{-# LANGUAGE ViewPatterns #-}
16+
917-- | 'Patch'es on 'Map' that can insert, delete, and move values from one key to
1018-- another
11−module Data.Patch.MapWithMove where
19+module Data.Patch.MapWithMove
20+ ( PatchMapWithMove
21+ ( PatchMapWithMove
22+ , unPatchMapWithMove
23+ , ..
24+ )
25+ , patchMapWithMove
26+ , patchMapWithMoveInsertAll
27+ , insertMapKey
28+ , moveMapKey
29+ , swapMapKey
30+ , deleteMapKey
31+ , unsafePatchMapWithMove
32+ , patchMapWithMoveNewElements
33+ , patchMapWithMoveNewElementsMap
34+ , patchThatSortsMapWith
35+ , patchThatChangesAndSortsMapWith
36+ , patchThatChangesMap
37+
38+ -- * Node Info
39+ , NodeInfo
40+ ( NodeInfo
41+ , _nodeInfo_to
42+ , _nodeInfo_from
43+ , ..
44+ )
45+ , bitraverseNodeInfo
46+ , nodeInfoMapFrom
47+ , nodeInfoMapMFrom
48+ , nodeInfoSetTo
49+
50+ -- * From
51+ , From
52+ ( From_Insert
53+ , From_Delete
54+ , From_Move
55+ , ..
56+ )
57+ , bitraverseFrom
1258
59+ -- * To
60+ , To
61+ ) where
62+
63+import Data.Coerce
64+import Data.Kind (Type)
1365import Data.Patch.Class
66+import Data.Patch.MapWithPatchingMove (PatchMapWithPatchingMove(..), To)
67+import qualified Data.Patch.MapWithPatchingMove as PM -- already a transparent synonym
1468
15−import Control.Arrow
16−import Control.Monad.Trans.State
17−import Data.Foldable
18−import Data.Function
69+import Control.Lens
1970import Data.List
2071import Data.Map (Map)
2172import qualified Data.Map as Map
22−import Data.Maybe
23−#if !MIN_VERSION_base(4,9,0)
24−import Data.Semigroup (Semigroup (..), (<>))
73+import Data.Proxy
74+#if !MIN_VERSION_base(4,11,0)
75+import Data.Semigroup (Semigroup (..))
2576#endif
26−import Data.Monoid.DecidablyEmpty
27−import qualified Data.Set as Set
28−import Data.These (These (..))
29−import Data.Tuple
77+import Data.Traversable (foldMapDefault)
3078
3179-- | Patch a Map with additions, deletions, and moves. Invariant: If key @k1@
3280-- is coming from @From_Move k2@, then key @k2@ should be going to @Just k1@,
3381-- and vice versa. There should never be any unpaired From/To keys.
34−newtype PatchMapWithMove k p = PatchMapWithMove (Map k (NodeInfo k p))
35−deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (PatchMapWithMove k p)
36−deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (PatchMapWithMove k p)
37−deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (PatchMapWithMove k p)
38−
39−-- | Holds the information about each key: where its new value should come from,
40−-- and where its old value should go to
41−data NodeInfo k p = NodeInfo
42− { _nodeInfo_from :: !(From k p)
43− -- ^ Where do we get the new value for this key?
44− , _nodeInfo_to :: !(To k)
45− -- ^ If the old value is being kept (i.e. moved rather than deleted or
46− -- replaced), where is it going?
82+newtype PatchMapWithMove k (v :: Type) = PatchMapWithMove'
83+ { -- | Extract the underlying 'PatchMapWithPatchingMove k (Proxy v)'
84+ unPatchMapWithMove' :: PatchMapWithPatchingMove k (Proxy v)
4785 }
48−deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (NodeInfo k p)
49−deriving instance (Read k, Read p, Read (PatchTarget p)) => Read (NodeInfo k p)
50−deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (NodeInfo k p)
51−deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (NodeInfo k p)
86+ deriving ( Show, Read, Eq, Ord
87+-- Haddock cannot handle documentation here before GHC 8.6
88+ ,
89+#if __GLASGOW_HASKELL__ >= 806
90+ -- | Compose patches having the same effect as applying the
91+ -- patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p .
92+ -- 'applyAlways' q@
93+#endif
94+ Semigroup
95+ , Monoid
96+ )
5297
53−-- | Describe how a key's new value should be produced
54−data From k p
55− = From_Insert (PatchTarget p) -- ^ Insert the given value here
56− | From_Delete -- ^ Delete the existing value, if any, from here
57− | From_Move !k !p -- ^ Move the value here from the given key, and apply the given patch
98+pattern Coerce :: Coercible a b => a -> b
99+pattern Coerce x <- (coerce -> x)
100+ where Coerce x = coerce x
101+
102+{-# COMPLETE PatchMapWithMove #-}
103+pattern PatchMapWithMove :: Map k (NodeInfo k v) -> PatchMapWithMove k v
104+-- | Extract the representation of the 'PatchMapWithMove' as a map of
105+-- 'NodeInfo'.
106+unPatchMapWithMove :: PatchMapWithMove k v -> Map k (NodeInfo k v)
107+pattern PatchMapWithMove { unPatchMapWithMove } = PatchMapWithMove' (PatchMapWithPatchingMove (Coerce unPatchMapWithMove))
108+
109+_PatchMapWithMove
110+ :: Iso
111+ (PatchMapWithMove k0 v0)
112+ (PatchMapWithMove k1 v1)
113+ (Map k0 (NodeInfo k0 v0))
114+ (Map k1 (NodeInfo k1 v1))
115+_PatchMapWithMove = iso unPatchMapWithMove PatchMapWithMove
58116
59−deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (From k p)
60−deriving instance (Read k, Read p, Read (PatchTarget p)) => Read (From k p)
61−deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (From k p)
62−deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (From k p)
117+instance Functor (PatchMapWithMove k) where
118+ fmap f = runIdentity . traverse (Identity . f)
63119
64−-- | Describe where a key's old value will go. If this is 'Just', that means
65−-- the key's old value will be moved to the given other key; if it is 'Nothing',
66−-- that means it will be deleted.
67−type To = Maybe
120+instance Foldable (PatchMapWithMove k) where
121+ foldMap = foldMapDefault
122+
123+instance Traversable (PatchMapWithMove k) where
124+ traverse =
125+ _PatchMapWithMove .
126+ traverse .
127+ traverse
128+
129+instance FunctorWithIndex k (PatchMapWithMove k)
130+instance FoldableWithIndex k (PatchMapWithMove k)
131+instance TraversableWithIndex k (PatchMapWithMove k) where
132+ itraverse = itraversed . Indexed
133+ itraversed =
134+ _PatchMapWithMove .>
135+ itraversed <.
136+ traverse
68137
69138-- | Create a 'PatchMapWithMove', validating it
70−patchMapWithMove
71− :: Ord k => Map k (NodeInfo k p) -> Maybe (PatchMapWithMove k p)
72−patchMapWithMove m = if valid then Just $ PatchMapWithMove m else Nothing
73− where valid = forwardLinks == backwardLinks
74− forwardLinks = Map.mapMaybe _nodeInfo_to m
75− backwardLinks = Map.fromList $ catMaybes $ flip fmap (Map.toList m) $ \(to, p) ->
76− case _nodeInfo_from p of
77− From_Move from _ -> Just (from, to)
78− _ -> Nothing
139+patchMapWithMove :: Ord k => Map k (NodeInfo k v) -> Maybe (PatchMapWithMove k v)
140+patchMapWithMove = fmap PatchMapWithMove' . PM.patchMapWithPatchingMove . coerce
79141
80142-- | Create a 'PatchMapWithMove' that inserts everything in the given 'Map'
81−patchMapWithMoveInsertAll
82− :: Map k (PatchTarget p) -> PatchMapWithMove k p
83−patchMapWithMoveInsertAll m = PatchMapWithMove $ flip fmap m $ \v -> NodeInfo
84− { _nodeInfo_from = From_Insert v
85− , _nodeInfo_to = Nothing
86− }
143+patchMapWithMoveInsertAll :: Map k v -> PatchMapWithMove k v
144+patchMapWithMoveInsertAll = PatchMapWithMove' . PM.patchMapWithPatchingMoveInsertAll
87145
88−-- | Extract the internal representation of the 'PatchMapWithMove'
89−unPatchMapWithMove
90− :: PatchMapWithMove k p -> Map k (NodeInfo k p)
91−unPatchMapWithMove (PatchMapWithMove p) = p
146+-- | Make a @'PatchMapWithMove' k v@ which has the effect of inserting or updating a value @v@ to the given key @k@, like 'Map.insert'.
147+insertMapKey :: k -> v -> PatchMapWithMove k v
148+insertMapKey k v = PatchMapWithMove' $ PM.insertMapKey k v
92149
93−-- | Make a @'PatchMapWithMove' k p@ which has the effect of inserting or updating a value @v@ to the given key @k@, like 'Map.insert'.
94−insertMapKey
95− :: k -> PatchTarget p -> PatchMapWithMove k p
96−insertMapKey k v = PatchMapWithMove . Map.singleton k $ NodeInfo (From_Insert v) Nothing
97−
98−-- |Make a @'PatchMapWithMove' k p@ which has the effect of moving the value from the first key @k@ to the second key @k@, equivalent to:
150+-- |Make a @'PatchMapWithMove' k v@ which has the effect of moving the value from the first key @k@ to the second key @k@, equivalent to:
99151--
100152-- @
101153-- 'Map.delete' src (maybe map ('Map.insert' dst) (Map.lookup src map))
102154-- @
103−moveMapKey
104− :: (DecidablyEmpty p, Patch p) => Ord k => k -> k -> PatchMapWithMove k p
105−moveMapKey src dst
106− | src == dst = mempty
107− | otherwise =
108− PatchMapWithMove $ Map.fromList
109− [ (dst, NodeInfo (From_Move src mempty) Nothing)
110− , (src, NodeInfo From_Delete (Just dst))
111− ]
112−
113−-- |Make a @'PatchMapWithMove' k p@ which has the effect of swapping two keys in the mapping, equivalent to:
155+moveMapKey :: Ord k => k -> k -> PatchMapWithMove k v
156+moveMapKey src dst = PatchMapWithMove' $ PM.moveMapKey src dst
157+
158+-- |Make a @'PatchMapWithMove' k v@ which has the effect of swapping two keys in the mapping, equivalent to:
114159--
115160-- @
116161-- let aMay = Map.lookup a map
117162-- bMay = Map.lookup b map
118−-- in maybe id (Map.insert a) (bMay `mplus` aMay)
119−-- . maybe id (Map.insert b) (aMay `mplus` bMay)
163+-- in maybe id (Map.insert a) (bMay <> aMay)
164+-- . maybe id (Map.insert b) (aMay <> bMay)
120165-- . Map.delete a . Map.delete b $ map
121166-- @
122−swapMapKey
123− :: (DecidablyEmpty p, Patch p) => Ord k => k -> k -> PatchMapWithMove k p
124−swapMapKey src dst
125− | src == dst = mempty
126− | otherwise =
127− PatchMapWithMove $ Map.fromList
128− [ (dst, NodeInfo (From_Move src mempty) (Just src))
129− , (src, NodeInfo (From_Move dst mempty) (Just dst))
130− ]
167+swapMapKey :: Ord k => k -> k -> PatchMapWithMove k v
168+swapMapKey src dst = PatchMapWithMove' $ PM.swapMapKey src dst
131169
132170-- |Make a @'PatchMapWithMove' k v@ which has the effect of deleting a key in the mapping, equivalent to 'Map.delete'.
133−deleteMapKey
134− :: k -> PatchMapWithMove k v
135−deleteMapKey k = PatchMapWithMove . Map.singleton k $ NodeInfo From_Delete Nothing
171+deleteMapKey :: k -> PatchMapWithMove k v
172+deleteMapKey = PatchMapWithMove' . PM.deleteMapKey
136173
137174-- | Wrap a @'Map' k (NodeInfo k v)@ representing patch changes into a @'PatchMapWithMove' k v@, without checking any invariants.
138175--
139176-- __Warning:__ when using this function, you must ensure that the invariants of 'PatchMapWithMove' are preserved; they will not be checked.
140−unsafePatchMapWithMove
141− :: Map k (NodeInfo k p) -> PatchMapWithMove k p
142−unsafePatchMapWithMove = PatchMapWithMove
177+unsafePatchMapWithMove :: Map k (NodeInfo k v) -> PatchMapWithMove k v
178+unsafePatchMapWithMove = coerce PM.unsafePatchMapWithPatchingMove
143179
144180-- | Apply the insertions, deletions, and moves to a given 'Map'
145−instance (Ord k, Patch p) => Patch (PatchMapWithMove k p) where
146− type PatchTarget (PatchMapWithMove k p) = Map k (PatchTarget p)
147− apply (PatchMapWithMove m) old = Just $! insertions `Map.union` (old `Map.difference` deletions) --TODO: return Nothing sometimes --Note: the strict application here is critical to ensuring that incremental merges don't hold onto all their prerequisite events forever; can we make this more robust?
148− where insertions = flip Map.mapMaybeWithKey m $ \_ ni -> case _nodeInfo_from ni of
149− From_Insert v -> Just v
150− From_Move k p -> applyAlways p <$> Map.lookup k old
151− From_Delete -> Nothing
152− deletions = flip Map.mapMaybeWithKey m $ \_ ni -> case _nodeInfo_from ni of
153− From_Delete -> Just ()
154− _ -> Nothing
155−
156−-- | Returns all the new elements that will be added to the 'Map'
157−patchMapWithMoveNewElements
158− :: PatchMapWithMove k p -> [PatchTarget p]
159−patchMapWithMoveNewElements = Map.elems . patchMapWithMoveNewElementsMap
181+instance Ord k => Patch (PatchMapWithMove k v) where
182+ type PatchTarget (PatchMapWithMove k v) = Map k v
183+ apply (PatchMapWithMove' p) = apply p
184+
185+-- | Returns all the new elements that will be added to the 'Map'.
186+patchMapWithMoveNewElements :: PatchMapWithMove k v -> [v]
187+patchMapWithMoveNewElements = PM.patchMapWithPatchingMoveNewElements . unPatchMapWithMove'
160188
161189-- | Return a @'Map' k v@ with all the inserts/updates from the given @'PatchMapWithMove' k v@.
162−patchMapWithMoveNewElementsMap
163− :: PatchMapWithMove k p -> Map k (PatchTarget p)
164−patchMapWithMoveNewElementsMap (PatchMapWithMove p) = Map.mapMaybe f p
165− where f ni = case _nodeInfo_from ni of
166− From_Insert v -> Just v
167− From_Move _ _ -> Nothing
168− From_Delete -> Nothing
190+patchMapWithMoveNewElementsMap :: PatchMapWithMove k v -> Map k v
191+patchMapWithMoveNewElementsMap = PM.patchMapWithPatchingMoveNewElementsMap . unPatchMapWithMove'
169192
170193-- | Create a 'PatchMapWithMove' that, if applied to the given 'Map', will sort
171194-- its values using the given ordering function. The set keys of the 'Map' is
172195-- not changed.
173−patchThatSortsMapWith
174− :: (Ord k, Monoid p)
175− => (PatchTarget p -> PatchTarget p -> Ordering)
176− -> Map k (PatchTarget p) -> PatchMapWithMove k p
177−patchThatSortsMapWith cmp m = PatchMapWithMove $ Map.fromList $ catMaybes $ zipWith g unsorted sorted
178− where unsorted = Map.toList m
179− sorted = sortBy (cmp `on` snd) unsorted
180− f (to, _) (from, _) = if to == from then Nothing else
181− Just (from, to)
182− reverseMapping = Map.fromList $ catMaybes $ zipWith f unsorted sorted
183− g (to, _) (from, _) = if to == from then Nothing else
184− let Just movingTo = Map.lookup from reverseMapping
185− in Just (to, NodeInfo (From_Move from mempty) $ Just movingTo)
196+patchThatSortsMapWith :: Ord k => (v -> v -> Ordering) -> Map k v -> PatchMapWithMove k v
197+patchThatSortsMapWith cmp = PatchMapWithMove' . PM.patchThatSortsMapWith cmp
186198
187199-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
188200-- will produce a 'Map' with the same values as the second 'Map' but with the
189201-- values sorted with the given ordering function.
190−patchThatChangesAndSortsMapWith
191− :: forall k p. (Ord k, Ord (PatchTarget p), Monoid p)
192− => (PatchTarget p -> PatchTarget p -> Ordering)
193− -> Map k (PatchTarget p) -> Map k (PatchTarget p) -> PatchMapWithMove k p
202+patchThatChangesAndSortsMapWith :: (Ord k, Ord v) => (v -> v -> Ordering) -> Map k v -> Map k v -> PatchMapWithMove k v
194203patchThatChangesAndSortsMapWith cmp oldByIndex newByIndexUnsorted = patchThatChangesMap oldByIndex newByIndex
195204 where newList = Map.toList newByIndexUnsorted
196205 newByIndex = Map.fromList $ zip (fst <$> newList) $ sortBy cmp $ snd <$> newList
197206
198207-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
199208-- will produce the second 'Map'.
200−patchThatChangesMap
201− :: (Ord k, Ord (PatchTarget p), Monoid p)
202− => Map k (PatchTarget p) -> Map k (PatchTarget p) -> PatchMapWithMove k p
203−patchThatChangesMap oldByIndex newByIndex = patch
204− where oldByValue = Map.fromListWith Set.union $ swap . first Set.singleton <$> Map.toList oldByIndex
205− (insertsAndMoves, unusedValuesByValue) = flip runState oldByValue $ do
206− let f k v = do
207− remainingValues <- get
208− let putRemainingKeys remainingKeys = put $ if Set.null remainingKeys
209− then Map.delete v remainingValues
210− else Map.insert v remainingKeys remainingValues
211− case Map.lookup v remainingValues of
212− Nothing -> return $ NodeInfo (From_Insert v) $ Just undefined -- There's no existing value we can take
213− Just fromKs ->
214− if k `Set.member` fromKs
215− then do
216− putRemainingKeys $ Set.delete k fromKs
217− return $ NodeInfo (From_Move k mempty) $ Just undefined -- There's an existing value, and it's here, so no patch necessary
218− else do
219− (fromK, remainingKeys) <- return . fromJust $ Set.minView fromKs -- There's an existing value, but it's not here; move it here
220− putRemainingKeys remainingKeys
221− return $ NodeInfo (From_Move fromK mempty) $ Just undefined
222− Map.traverseWithKey f newByIndex
223− unusedOldKeys = fold unusedValuesByValue
224− pointlessMove k = \case
225− From_Move k' _ | k == k' -> True
226− _ -> False
227− keyWasMoved k = if k `Map.member` oldByIndex && not (k `Set.member` unusedOldKeys)
228− then Just undefined
229− else Nothing
230− patch = unsafePatchMapWithMove $ Map.filterWithKey (\k -> not . pointlessMove k . _nodeInfo_from) $ Map.mergeWithKey (\k a _ -> Just $ nodeInfoSetTo (keyWasMoved k) a) (Map.mapWithKey $ \k -> nodeInfoSetTo $ keyWasMoved k) (Map.mapWithKey $ \k _ -> NodeInfo From_Delete $ keyWasMoved k) insertsAndMoves oldByIndex
209+patchThatChangesMap :: (Ord k, Ord v) => Map k v -> Map k v -> PatchMapWithMove k v
210+patchThatChangesMap oldByIndex newByIndex = PatchMapWithMove' $
211+ PM.patchThatChangesMap oldByIndex newByIndex
212+
213+--
214+-- NodeInfo
215+--
216+
217+-- | Holds the information about each key: where its new value should come from,
218+-- and where its old value should go to
219+newtype NodeInfo k (v :: Type) = NodeInfo' { unNodeInfo' :: PM.NodeInfo k (Proxy v) }
220+
221+deriving instance (Show k, Show p) => Show (NodeInfo k p)
222+deriving instance (Read k, Read p) => Read (NodeInfo k p)
223+deriving instance (Eq k, Eq p) => Eq (NodeInfo k p)
224+deriving instance (Ord k, Ord p) => Ord (NodeInfo k p)
225+
226+{-# COMPLETE NodeInfo #-}
227+pattern NodeInfo :: To k -> From k v -> NodeInfo k v
228+_nodeInfo_to :: NodeInfo k v -> To k
229+_nodeInfo_from :: NodeInfo k v -> From k v
230+pattern NodeInfo { _nodeInfo_to, _nodeInfo_from } = NodeInfo'
231+ PM.NodeInfo
232+ { PM._nodeInfo_to = _nodeInfo_to
233+ , PM._nodeInfo_from = Coerce _nodeInfo_from
234+ }
235+
236+_NodeInfo
237+ :: Iso
238+ (NodeInfo k0 v0)
239+ (NodeInfo k1 v1)
240+ (PM.NodeInfo k0 (Proxy v0))
241+ (PM.NodeInfo k1 (Proxy v1))
242+_NodeInfo = iso unNodeInfo' NodeInfo'
243+
244+instance Functor (NodeInfo k) where
245+ fmap f = runIdentity . traverse (Identity . f)
246+
247+instance Foldable (NodeInfo k) where
248+ foldMap = foldMapDefault
249+
250+instance Traversable (NodeInfo k) where
251+ traverse = bitraverseNodeInfo pure
252+
253+bitraverseNodeInfo
254+ :: Applicative f
255+ => (k0 -> f k1)
256+ -> (v0 -> f v1)
257+ -> NodeInfo k0 v0 -> f (NodeInfo k1 v1)
258+bitraverseNodeInfo fk fv = fmap NodeInfo'
259+ . PM.bitraverseNodeInfo fk (\ ~Proxy -> pure Proxy) fv
260+ . coerce
231261
232262-- | Change the 'From' value of a 'NodeInfo'
233−nodeInfoMapFrom
234− :: (From k v -> From k v) -> NodeInfo k v -> NodeInfo k v
235−nodeInfoMapFrom f ni = ni { _nodeInfo_from = f $ _nodeInfo_from ni }
263+nodeInfoMapFrom :: (From k v -> From k v) -> NodeInfo k v -> NodeInfo k v
264+nodeInfoMapFrom f = coerce $ PM.nodeInfoMapFrom (unFrom' . f . From')
236265
237266-- | Change the 'From' value of a 'NodeInfo', using a 'Functor' (or
238267-- 'Applicative', 'Monad', etc.) action to get the new value
239268nodeInfoMapMFrom
240− :: Functor f => (From k v -> f (From k v)) -> NodeInfo k v -> f (NodeInfo k v)
241−nodeInfoMapMFrom f ni = fmap (\result -> ni { _nodeInfo_from = result }) $ f $ _nodeInfo_from ni
269+ :: Functor f
270+ => (From k v -> f (From k v))
271+ -> NodeInfo k v -> f (NodeInfo k v)
272+nodeInfoMapMFrom f = fmap NodeInfo'
273+ . PM.nodeInfoMapMFrom (fmap unFrom' . f . From')
274+ . coerce
242275
243276-- | Set the 'To' field of a 'NodeInfo'
244−nodeInfoSetTo
245− :: To k -> NodeInfo k v -> NodeInfo k v
246−nodeInfoSetTo to ni = ni { _nodeInfo_to = to }
247−
248−-- |Helper data structure used for composing patches using the monoid instance.
249−data Fixup k v
250− = Fixup_Delete
251− | Fixup_Update (These (From k v) (To k))
252−
253−-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
254−instance ( Ord k
255− , Monoid p
256− , DecidablyEmpty p
257− , Patch p
258− ) => Semigroup (PatchMapWithMove k p) where
259− PatchMapWithMove ma <> PatchMapWithMove mb = PatchMapWithMove m
260− where
261− connections = Map.toList $ Map.intersectionWithKey (\_ a b -> (_nodeInfo_to a, _nodeInfo_from b)) ma mb
262− h :: (k, (Maybe k, From k p)) -> [(k, Fixup k p)]
263− h (_, (mToAfter, editBefore)) = case (mToAfter, editBefore) of
264− (Just toAfter, From_Move fromBefore p)
265− | fromBefore == toAfter && isNull p
266− -> [(toAfter, Fixup_Delete)]
267− | otherwise
268− -> [ (toAfter, Fixup_Update (This editBefore))
269− , (fromBefore, Fixup_Update (That mToAfter))
270− ]
271− (Nothing, From_Move fromBefore _) -> [(fromBefore, Fixup_Update (That mToAfter))] -- The item is destroyed in the second patch, so indicate that it is destroyed in the source map
272− (Just toAfter, _) -> [(toAfter, Fixup_Update (This editBefore))]
273− (Nothing, _) -> []
274− mergeFixups _ Fixup_Delete Fixup_Delete = Fixup_Delete
275− mergeFixups _ (Fixup_Update a) (Fixup_Update b)
276− | This x <- a, That y <- b
277− = Fixup_Update $ These x y
278− | That y <- a, This x <- b
279− = Fixup_Update $ These x y
280− mergeFixups _ _ _ = error "PatchMapWithMove: incompatible fixups"
281− fixups = Map.fromListWithKey mergeFixups $ concatMap h connections
282− combineNodeInfos _ nia nib = NodeInfo
283− { _nodeInfo_from = _nodeInfo_from nia
284− , _nodeInfo_to = _nodeInfo_to nib
285− }
286− applyFixup _ ni = \case
287− Fixup_Delete -> Nothing
288− Fixup_Update u -> Just $ NodeInfo
289− { _nodeInfo_from = case _nodeInfo_from ni of
290− f@(From_Move _ p') -> case getHere u of -- The `from` fixup comes from the "old" patch
291− Nothing -> f -- If there's no `from` fixup, just use the "new" `from`
292− Just (From_Insert v) -> From_Insert $ applyAlways p' v
293− Just From_Delete -> From_Delete
294− Just (From_Move oldKey p) -> From_Move oldKey $ p' <> p
295− _ -> error "PatchMapWithMove: fixup for non-move From"
296− , _nodeInfo_to = fromMaybe (_nodeInfo_to ni) $ getThere u
297− }
298− m = Map.differenceWithKey applyFixup (Map.unionWithKey combineNodeInfos ma mb) fixups
299− getHere :: These a b -> Maybe a
300− getHere = \case
301− This a -> Just a
302− These a _ -> Just a
303− That _ -> Nothing
304− getThere :: These a b -> Maybe b
305− getThere = \case
306− This _ -> Nothing
307− These _ b -> Just b
308− That b -> Just b
309−
310−--TODO: Figure out how to implement this in terms of PatchDMapWithMove rather than duplicating it here
311−-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
312−instance ( Ord k
313− , Monoid p
314− , DecidablyEmpty p
315− , Patch p
316− ) => Monoid (PatchMapWithMove k p) where
317− mempty = PatchMapWithMove mempty
318− mappend = (<>)
277+nodeInfoSetTo :: To k -> NodeInfo k v -> NodeInfo k v
278+nodeInfoSetTo = coerce . PM.nodeInfoSetTo
279+
280+--
281+-- From
282+--
283+
284+-- | Describe how a key's new value should be produced
285+newtype From k (v :: Type) = From' { unFrom' :: PM.From k (Proxy v) }
286+
287+{-# COMPLETE From_Insert, From_Delete, From_Move #-}
288+
289+-- | Insert the given value here
290+pattern From_Insert :: v -> From k v
291+pattern From_Insert v = From' (PM.From_Insert v)
292+
293+-- | Delete the existing value, if any, from here
294+pattern From_Delete :: From k v
295+pattern From_Delete = From' PM.From_Delete
296+
297+-- | Move the value here from the given key
298+pattern From_Move :: k -> From k v
299+pattern From_Move k = From' (PM.From_Move k Proxy)
300+
301+bitraverseFrom
302+ :: Applicative f
303+ => (k0 -> f k1)
304+ -> (v0 -> f v1)
305+ -> From k0 v0 -> f (From k1 v1)
306+bitraverseFrom fk fv = fmap From'
307+ . PM.bitraverseFrom fk (\ ~Proxy -> pure Proxy) fv
308+ . coerce
309+
310+makeWrapped ''PatchMapWithMove
311+makeWrapped ''NodeInfo
312+makeWrapped ''From