@@ -1,312 +1,243 @@
1−{-# LANGUAGE CPP #-}
2−{-# LANGUAGE DeriveTraversable #-}
31{-# LANGUAGE FlexibleContexts #-}
4−{-# LANGUAGE FlexibleInstances #-}
5−{-# LANGUAGE GeneralizedNewtypeDeriving #-}
62{-# LANGUAGE LambdaCase #-}
7−{-# LANGUAGE MultiParamTypeClasses #-}
83{-# LANGUAGE PatternGuards #-}
9−{-# LANGUAGE PatternSynonyms #-}
104{-# LANGUAGE ScopedTypeVariables #-}
115{-# LANGUAGE StandaloneDeriving #-}
12−{-# LANGUAGE TemplateHaskell #-}
13−{-# LANGUAGE TypeApplications #-}
146{-# LANGUAGE TypeFamilies #-}
15−{-# LANGUAGE ViewPatterns #-}
16−
7+{-# LANGUAGE UndecidableInstances #-}
178-- | 'Patch'es on 'Map' that can insert, delete, and move values from one key to
189-- 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
10+module Reflex.Patch.MapWithMove where
5811
59− -- * To
60− , To
61− ) where
12+import Reflex.Patch.Class
6213
63−import Data.Coerce
64−import Data.Kind (Type)
65−import Data.Patch.Class
66−import Data.Patch.MapWithPatchingMove (PatchMapWithPatchingMove(..), To)
67−import qualified Data.Patch.MapWithPatchingMove as PM -- already a transparent synonym
68−
69−import Control.Lens
14+import Control.Arrow
15+import Control.Monad.State
16+import Data.Foldable
17+import Data.Function
7018import Data.List
7119import Data.Map (Map)
7220import qualified Data.Map as Map
73−import Data.Proxy
74−#if !MIN_VERSION_base(4,11,0)
75−import Data.Semigroup (Semigroup (..))
76−#endif
77−import Data.Traversable (foldMapDefault)
78−
79−-- | Patch a Map with additions, deletions, and moves. Invariant: If key @k1@
80−-- is coming from @From_Move k2@, then key @k2@ should be going to @Just k1@,
21+import Data.Maybe
22+import Data.Semigroup
23+import qualified Data.Set as Set
24+import Data.These
25+import Data.Tuple
26+
27+-- | Patch a DMap with additions, deletions, and moves. Invariant: If key @k1@
28+-- is coming from @From_Move k@, then key @k2@ should be going to @Just k1@,
8129-- 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− )
97−
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)
30+newtype PatchMapWithMove k p = PatchMapWithMove (Map k (NodeInfo k p))
31+deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (PatchMapWithMove k p)
32+deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (PatchMapWithMove k p)
33+deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (PatchMapWithMove k p)
11934
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
35+-- | Holds the information about each key: where its new value should come from,
36+-- and where its old value should go to
37+data NodeInfo k p = NodeInfo
38+ { _nodeInfo_from :: !(From k p)
39+ -- ^ Where do we get the new value for this key?
40+ , _nodeInfo_to :: !(To k)
41+ -- ^ If the old value is being kept (i.e. moved rather than deleted or
42+ -- replaced), where is it going?
43+ }
44+deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (NodeInfo k p)
45+deriving instance (Read k, Read p, Read (PatchTarget p)) => Read (NodeInfo k p)
46+deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (NodeInfo k p)
47+deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (NodeInfo k p)
13748
13849-- | 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
50+patchMapWithMove :: Ord k => Map k (NodeInfo k p) -> Maybe (PatchMapWithMove k p)
51+patchMapWithMove m = if valid then Just $ PatchMapWithMove m else Nothing
52+ where valid = forwardLinks == backwardLinks
53+ forwardLinks = Map.mapMaybe _nodeInfo_to m
54+ backwardLinks = Map.fromList $ catMaybes $ flip fmap (Map.toList m) $ \(to, p) ->
55+ case _nodeInfo_from p of
56+ From_Move from _ -> Just (from, to)
57+ _ -> Nothing
14158
14259-- | Create a 'PatchMapWithMove' that inserts everything in the given 'Map'
143−patchMapWithMoveInsertAll :: Map k v -> PatchMapWithMove k v
144−patchMapWithMoveInsertAll = PatchMapWithMove' . PM.patchMapWithPatchingMoveInsertAll
60+patchMapWithMoveInsertAll :: Map k (PatchTarget p) -> PatchMapWithMove k p
61+patchMapWithMoveInsertAll m = PatchMapWithMove $ flip fmap m $ \v -> NodeInfo
62+ { _nodeInfo_from = From_Insert v
63+ , _nodeInfo_to = Nothing
64+ }
14565
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
66+-- | Extract the internal representation of the 'PatchMapWithMove'
67+unPatchMapWithMove :: PatchMapWithMove k p -> Map k (NodeInfo k p)
68+unPatchMapWithMove (PatchMapWithMove p) = p
14969
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:
151−--
152−-- @
153−-- 'Map.delete' src (maybe map ('Map.insert' dst) (Map.lookup src map))
154−-- @
155−moveMapKey :: Ord k => k -> k -> PatchMapWithMove k v
156−moveMapKey src dst = PatchMapWithMove' $ PM.moveMapKey src dst
70+-- | Warning: when using this function, you must ensure that the invariants of
71+-- 'PatchMapWithMove' are preserved; they will not be checked.
72+unsafePatchMapWithMove :: Map k (NodeInfo k p) -> PatchMapWithMove k p
73+unsafePatchMapWithMove = PatchMapWithMove
15774
158−-- |Make a @'PatchMapWithMove' k v@ which has the effect of swapping two keys in the mapping, equivalent to:
159−--
160−-- @
161−-- let aMay = Map.lookup a map
162−-- bMay = Map.lookup b map
163−-- in maybe id (Map.insert a) (bMay <> aMay)
164−-- . maybe id (Map.insert b) (aMay <> bMay)
165−-- . Map.delete a . Map.delete b $ map
166−-- @
167−swapMapKey :: Ord k => k -> k -> PatchMapWithMove k v
168−swapMapKey src dst = PatchMapWithMove' $ PM.swapMapKey src dst
75+-- | Describe how a key's new value should be produced
76+data From k p
77+ = From_Insert (PatchTarget p) -- ^ Insert the given value here
78+ | From_Delete -- ^ Delete the existing value, if any, from here
79+ | From_Move !k !p -- ^ Move the value here from the given key, and apply the given patch
16980
170−-- |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
81+deriving instance (Show k, Show p, Show (PatchTarget p)) => Show (From k p)
82+deriving instance (Read k, Read p, Read (PatchTarget p)) => Read (From k p)
83+deriving instance (Eq k, Eq p, Eq (PatchTarget p)) => Eq (From k p)
84+deriving instance (Ord k, Ord p, Ord (PatchTarget p)) => Ord (From k p)
17385
174−-- | Wrap a @'Map' k (NodeInfo k v)@ representing patch changes into a @'PatchMapWithMove' k v@, without checking any invariants.
175−--
176−-- __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
86+-- | Describe where a key's old value will go. If this is 'Just', that means
87+-- the key's old value will be moved to the given other key; if it is 'Nothing',
88+-- that means it will be deleted.
89+type To = Maybe
17990
18091-- | 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'
188−
189−-- | 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'
92+instance (Ord k, Patch p) => Patch (PatchMapWithMove k p) where
93+ type PatchTarget (PatchMapWithMove k p) = Map k (PatchTarget p)
94+ 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?
95+ where insertions = flip Map.mapMaybeWithKey m $ \_ ni -> case _nodeInfo_from ni of
96+ From_Insert v -> Just v
97+ From_Move k p -> applyAlways p <$> Map.lookup k old
98+ From_Delete -> Nothing
99+ deletions = flip Map.mapMaybeWithKey m $ \_ ni -> case _nodeInfo_from ni of
100+ From_Delete -> Just ()
101+ _ -> Nothing
102+
103+-- | Returns all the new elements that will be added to the 'Map'
104+patchMapWithMoveNewElements :: PatchMapWithMove k p -> [PatchTarget p]
105+patchMapWithMoveNewElements = Map.elems . patchMapWithMoveNewElementsMap
106+
107+patchMapWithMoveNewElementsMap :: PatchMapWithMove k p -> Map k (PatchTarget p)
108+patchMapWithMoveNewElementsMap (PatchMapWithMove p) = Map.mapMaybe f p
109+ where f ni = case _nodeInfo_from ni of
110+ From_Insert v -> Just v
111+ From_Move _ _ -> Nothing
112+ From_Delete -> Nothing
192113
193114-- | Create a 'PatchMapWithMove' that, if applied to the given 'Map', will sort
194115-- its values using the given ordering function. The set keys of the 'Map' is
195116-- not changed.
196−patchThatSortsMapWith :: Ord k => (v -> v -> Ordering) -> Map k v -> PatchMapWithMove k v
197−patchThatSortsMapWith cmp = PatchMapWithMove' . PM.patchThatSortsMapWith cmp
117+patchThatSortsMapWith :: (Ord k, Monoid p) => (PatchTarget p -> PatchTarget p -> Ordering) -> Map k (PatchTarget p) -> PatchMapWithMove k p
118+patchThatSortsMapWith cmp m = PatchMapWithMove $ Map.fromList $ catMaybes $ zipWith g unsorted sorted
119+ where unsorted = Map.toList m
120+ sorted = sortBy (cmp `on` snd) unsorted
121+ f (to, _) (from, _) = if to == from then Nothing else
122+ Just (from, to)
123+ reverseMapping = Map.fromList $ catMaybes $ zipWith f unsorted sorted
124+ g (to, _) (from, _) = if to == from then Nothing else
125+ let Just movingTo = Map.lookup from reverseMapping
126+ in Just (to, NodeInfo (From_Move from mempty) $ Just movingTo)
198127
199128-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
200129-- will produce a 'Map' with the same values as the second 'Map' but with the
201130-- 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
131+patchThatChangesAndSortsMapWith :: forall k p. (Ord k, Ord (PatchTarget p), Monoid p) => (PatchTarget p -> PatchTarget p -> Ordering) -> Map k (PatchTarget p) -> Map k (PatchTarget p) -> PatchMapWithMove k p
203132patchThatChangesAndSortsMapWith cmp oldByIndex newByIndexUnsorted = patchThatChangesMap oldByIndex newByIndex
204133 where newList = Map.toList newByIndexUnsorted
205134 newByIndex = Map.fromList $ zip (fst <$> newList) $ sortBy cmp $ snd <$> newList
206135
207136-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
208137-- 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
138+patchThatChangesMap :: (Ord k, Ord (PatchTarget p), Monoid p) => Map k (PatchTarget p) -> Map k (PatchTarget p) -> PatchMapWithMove k p
139+patchThatChangesMap oldByIndex newByIndex = patch
140+ where oldByValue = Map.fromListWith Set.union $ swap . first Set.singleton <$> Map.toList oldByIndex
141+ (insertsAndMoves, unusedValuesByValue) = flip runState oldByValue $ do
142+ let f k v = do
143+ remainingValues <- get
144+ let putRemainingKeys remainingKeys = put $ if Set.null remainingKeys
145+ then Map.delete v remainingValues
146+ else Map.insert v remainingKeys remainingValues
147+ case Map.lookup v remainingValues of
148+ Nothing -> return $ NodeInfo (From_Insert v) $ Just undefined -- There's no existing value we can take
149+ Just fromKs ->
150+ if k `Set.member` fromKs
151+ then do
152+ putRemainingKeys $ Set.delete k fromKs
153+ return $ NodeInfo (From_Move k mempty) $ Just undefined -- There's an existing value, and it's here, so no patch necessary
154+ else do
155+ (fromK, remainingKeys) <- return . fromJust $ Set.minView fromKs -- There's an existing value, but it's not here; move it here
156+ putRemainingKeys remainingKeys
157+ return $ NodeInfo (From_Move fromK mempty) $ Just undefined
158+ Map.traverseWithKey f newByIndex
159+ unusedOldKeys = fold unusedValuesByValue
160+ pointlessMove k = \case
161+ From_Move k' _ | k == k' -> True
162+ _ -> False
163+ keyWasMoved k = if k `Map.member` oldByIndex && not (k `Set.member` unusedOldKeys)
164+ then Just undefined
165+ else Nothing
166+ 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
261167
262168-- | Change the 'From' value of a 'NodeInfo'
263169nodeInfoMapFrom :: (From k v -> From k v) -> NodeInfo k v -> NodeInfo k v
264−nodeInfoMapFrom f = coerce $ PM.nodeInfoMapFrom (unFrom' . f . From')
170+nodeInfoMapFrom f ni = ni { _nodeInfo_from = f $ _nodeInfo_from ni }
265171
266172-- | Change the 'From' value of a 'NodeInfo', using a 'Functor' (or
267173-- 'Applicative', 'Monad', etc.) action to get the new value
268−nodeInfoMapMFrom
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
174+nodeInfoMapMFrom :: Functor f => (From k v -> f (From k v)) -> NodeInfo k v -> f (NodeInfo k v)
175+nodeInfoMapMFrom f ni = fmap (\result -> ni { _nodeInfo_from = result }) $ f $ _nodeInfo_from ni
275176
276177-- | Set the 'To' field of a 'NodeInfo'
277178nodeInfoSetTo :: 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
179+nodeInfoSetTo to ni = ni { _nodeInfo_to = to }
180+
181+-- |Helper data structure used for composing patches using the monoid instance.
182+data Fixup k v
183+ = Fixup_Delete
184+ | Fixup_Update (These (From k v) (To k))
185+
186+-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
187+instance (Ord k, Monoid p, Eq p, Patch p) => Semigroup (PatchMapWithMove k p) where
188+ PatchMapWithMove ma <> PatchMapWithMove mb = PatchMapWithMove m
189+ where
190+ connections = Map.toList $ Map.intersectionWithKey (\_ a b -> (_nodeInfo_to a, _nodeInfo_from b)) ma mb
191+ h :: (k, (Maybe k, From k p)) -> [(k, Fixup k p)]
192+ h (_, (mToAfter, editBefore)) = case (mToAfter, editBefore) of
193+ (Just toAfter, From_Move fromBefore p)
194+ | fromBefore == toAfter && p == mempty
195+ -> [(toAfter, Fixup_Delete)]
196+ | otherwise
197+ -> [ (toAfter, Fixup_Update (This editBefore))
198+ , (fromBefore, Fixup_Update (That mToAfter))
199+ ]
200+ (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
201+ (Just toAfter, _) -> [(toAfter, Fixup_Update (This editBefore))]
202+ (Nothing, _) -> []
203+ mergeFixups _ Fixup_Delete Fixup_Delete = Fixup_Delete
204+ mergeFixups _ (Fixup_Update a) (Fixup_Update b)
205+ | This x <- a, That y <- b
206+ = Fixup_Update $ These x y
207+ | That y <- a, This x <- b
208+ = Fixup_Update $ These x y
209+ mergeFixups _ _ _ = error "PatchMapWithMove: incompatible fixups"
210+ fixups = Map.fromListWithKey mergeFixups $ concatMap h connections
211+ combineNodeInfos _ nia nib = NodeInfo
212+ { _nodeInfo_from = _nodeInfo_from nia
213+ , _nodeInfo_to = _nodeInfo_to nib
214+ }
215+ applyFixup _ ni = \case
216+ Fixup_Delete -> Nothing
217+ Fixup_Update u -> Just $ NodeInfo
218+ { _nodeInfo_from = case _nodeInfo_from ni of
219+ f@(From_Move _ p') -> case getHere u of -- The `from` fixup comes from the "old" patch
220+ Nothing -> f -- If there's no `from` fixup, just use the "new" `from`
221+ Just (From_Insert v) -> From_Insert $ applyAlways p' v
222+ Just From_Delete -> From_Delete
223+ Just (From_Move oldKey p) -> From_Move oldKey $ p' <> p
224+ _ -> error "PatchMapWithMove: fixup for non-move From"
225+ , _nodeInfo_to = fromMaybe (_nodeInfo_to ni) $ getThere u
226+ }
227+ m = Map.differenceWithKey applyFixup (Map.unionWithKey combineNodeInfos ma mb) fixups
228+ getHere :: These a b -> Maybe a
229+ getHere = \case
230+ This a -> Just a
231+ These a _ -> Just a
232+ That _ -> Nothing
233+ getThere :: These a b -> Maybe b
234+ getThere = \case
235+ This _ -> Nothing
236+ These _ b -> Just b
237+ That b -> Just b
238+
239+--TODO: Figure out how to implement this in terms of PatchDMapWithMove rather than duplicating it here
240+-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
241+instance (Ord k, Monoid p, Eq p, Patch p) => Monoid (PatchMapWithMove k p) where
242+ mempty = PatchMapWithMove mempty
243+ mappend = (<>)