@@ -1,312 +1,318 @@
11{-# LANGUAGE CPP #-}
2−{-# LANGUAGE DeriveTraversable #-}
32{-# LANGUAGE FlexibleContexts #-}
4−{-# LANGUAGE FlexibleInstances #-}
5−{-# LANGUAGE GeneralizedNewtypeDeriving #-}
63{-# LANGUAGE LambdaCase #-}
7−{-# LANGUAGE MultiParamTypeClasses #-}
84{-# LANGUAGE PatternGuards #-}
9−{-# LANGUAGE PatternSynonyms #-}
105{-# LANGUAGE ScopedTypeVariables #-}
116{-# LANGUAGE StandaloneDeriving #-}
12−{-# LANGUAGE TemplateHaskell #-}
13−{-# LANGUAGE TypeApplications #-}
147{-# LANGUAGE TypeFamilies #-}
15−{-# LANGUAGE ViewPatterns #-}
16−
8+{-# LANGUAGE UndecidableInstances #-}
179-- | 'Patch'es on 'Map' that can insert, delete, and move values from one key to
1810-- another
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
11+module Data.Patch.MapWithMove where
5812
59− -- * To
60− , To
61− ) where
62−
63−import Data.Coerce
64−import Data.Kind (Type)
6513import Data.Patch.Class
66−import Data.Patch.MapWithPatchingMove (PatchMapWithPatchingMove(..), To)
67−import qualified Data.Patch.MapWithPatchingMove as PM -- already a transparent synonym
6814
69−import Control.Lens
15+import Control.Arrow
16+import Control.Monad.Trans.State
17+import Data.Foldable
18+import Data.Function
7019import Data.List
7120import Data.Map (Map)
7221import qualified Data.Map as Map
73−import Data.Proxy
74−#if !MIN_VERSION_base(4,11,0)
75−import Data.Semigroup (Semigroup (..))
22+import Data.Maybe
23+#if !MIN_VERSION_base(4,9,0)
24+import Data.Semigroup (Semigroup (..), (<>))
7625#endif
77−import Data.Traversable (foldMapDefault)
26+import Data.Monoid.DecidablyEmpty
27+import qualified Data.Set as Set
28+import Data.These (These (..))
29+import Data.Tuple
7830
7931-- | Patch a Map with additions, deletions, and moves. Invariant: If key @k1@
8032-- is coming from @From_Move k2@, then key @k2@ should be going to @Just k1@,
8133-- and vice versa. There should never be any unpaired From/To keys.
82−newtype PatchMapWithMove k (v :: Type) = PatchMapWithMove'
83− { -- | Extract the underlying 'PatchMapWithPatchingMove k (Proxy v)'
84− unPatchMapWithMove' :: PatchMapWithPatchingMove k (Proxy v)
85− }
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− )
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)
9738
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
116−
117−instance Functor (PatchMapWithMove k) where
118− fmap f = runIdentity . traverse (Identity . f)
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?
47+ }
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)
11952
120−instance Foldable (PatchMapWithMove k) where
121− foldMap = foldMapDefault
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
12258
123−instance Traversable (PatchMapWithMove k) where
124− traverse =
125− _PatchMapWithMove .
126− traverse .
127− traverse
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)
12863
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
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
13768
13869-- | Create a 'PatchMapWithMove', validating it
139−patchMapWithMove :: Ord k => Map k (NodeInfo k v) -> Maybe (PatchMapWithMove k v)
140−patchMapWithMove = fmap PatchMapWithMove' . PM.patchMapWithPatchingMove . coerce
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
14179
14280-- | Create a 'PatchMapWithMove' that inserts everything in the given 'Map'
143−patchMapWithMoveInsertAll :: Map k v -> PatchMapWithMove k v
144−patchMapWithMoveInsertAll = PatchMapWithMove' . PM.patchMapWithPatchingMoveInsertAll
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+ }
14587
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
88+-- | Extract the internal representation of the 'PatchMapWithMove'
89+unPatchMapWithMove
90+ :: PatchMapWithMove k p -> Map k (NodeInfo k p)
91+unPatchMapWithMove (PatchMapWithMove p) = p
14992
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:
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:
15199--
152100-- @
153101-- 'Map.delete' src (maybe map ('Map.insert' dst) (Map.lookup src map))
154102-- @
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:
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:
159114--
160115-- @
161116-- let aMay = Map.lookup a map
162117-- bMay = Map.lookup b map
163−-- in maybe id (Map.insert a) (bMay <> aMay)
164−-- . maybe id (Map.insert b) (aMay <> bMay)
118+-- in maybe id (Map.insert a) (bMay `mplus` aMay)
119+-- . maybe id (Map.insert b) (aMay `mplus` bMay)
165120-- . Map.delete a . Map.delete b $ map
166121-- @
167−swapMapKey :: Ord k => k -> k -> PatchMapWithMove k v
168−swapMapKey src dst = PatchMapWithMove' $ PM.swapMapKey src dst
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+ ]
169131
170132-- |Make a @'PatchMapWithMove' k v@ which has the effect of deleting a key in the mapping, equivalent to 'Map.delete'.
171−deleteMapKey :: k -> PatchMapWithMove k v
172−deleteMapKey = PatchMapWithMove' . PM.deleteMapKey
133+deleteMapKey
134+ :: k -> PatchMapWithMove k v
135+deleteMapKey k = PatchMapWithMove . Map.singleton k $ NodeInfo From_Delete Nothing
173136
174137-- | Wrap a @'Map' k (NodeInfo k v)@ representing patch changes into a @'PatchMapWithMove' k v@, without checking any invariants.
175138--
176139-- __Warning:__ when using this function, you must ensure that the invariants of 'PatchMapWithMove' are preserved; they will not be checked.
177−unsafePatchMapWithMove :: Map k (NodeInfo k v) -> PatchMapWithMove k v
178−unsafePatchMapWithMove = coerce PM.unsafePatchMapWithPatchingMove
140+unsafePatchMapWithMove
141+ :: Map k (NodeInfo k p) -> PatchMapWithMove k p
142+unsafePatchMapWithMove = PatchMapWithMove
179143
180144-- | Apply the insertions, deletions, and moves to a given 'Map'
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'
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
188160
189161-- | Return a @'Map' k v@ with all the inserts/updates from the given @'PatchMapWithMove' k v@.
190−patchMapWithMoveNewElementsMap :: PatchMapWithMove k v -> Map k v
191−patchMapWithMoveNewElementsMap = PM.patchMapWithPatchingMoveNewElementsMap . unPatchMapWithMove'
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
192169
193170-- | Create a 'PatchMapWithMove' that, if applied to the given 'Map', will sort
194171-- its values using the given ordering function. The set keys of the 'Map' is
195172-- not changed.
196−patchThatSortsMapWith :: Ord k => (v -> v -> Ordering) -> Map k v -> PatchMapWithMove k v
197−patchThatSortsMapWith cmp = PatchMapWithMove' . PM.patchThatSortsMapWith cmp
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)
198186
199187-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
200188-- will produce a 'Map' with the same values as the second 'Map' but with the
201189-- values sorted with the given ordering function.
202−patchThatChangesAndSortsMapWith :: (Ord k, Ord v) => (v -> v -> Ordering) -> Map k v -> Map k v -> PatchMapWithMove k v
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
203194patchThatChangesAndSortsMapWith cmp oldByIndex newByIndexUnsorted = patchThatChangesMap oldByIndex newByIndex
204195 where newList = Map.toList newByIndexUnsorted
205196 newByIndex = Map.fromList $ zip (fst <$> newList) $ sortBy cmp $ snd <$> newList
206197
207198-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
208199-- will produce the second 'Map'.
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
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
261231
262232-- | Change the 'From' value of a 'NodeInfo'
263−nodeInfoMapFrom :: (From k v -> From k v) -> NodeInfo k v -> NodeInfo k v
264−nodeInfoMapFrom f = coerce $ PM.nodeInfoMapFrom (unFrom' . f . From')
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 }
265236
266237-- | Change the 'From' value of a 'NodeInfo', using a 'Functor' (or
267238-- 'Applicative', 'Monad', etc.) action to get the new value
268239nodeInfoMapMFrom
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
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
275242
276243-- | Set the 'To' field of a 'NodeInfo'
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
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 = (<>)