@@ -2,97 +2,150 @@
22{-# LANGUAGE DeriveTraversable #-}
33{-# LANGUAGE FlexibleContexts #-}
44{-# LANGUAGE FlexibleInstances #-}
5+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
56{-# LANGUAGE LambdaCase #-}
67{-# LANGUAGE MultiParamTypeClasses #-}
78{-# LANGUAGE PatternGuards #-}
9+{-# LANGUAGE PatternSynonyms #-}
810{-# LANGUAGE ScopedTypeVariables #-}
11+{-# LANGUAGE StandaloneDeriving #-}
912{-# LANGUAGE TemplateHaskell #-}
1013{-# LANGUAGE TypeApplications #-}
1114{-# LANGUAGE TypeFamilies #-}
15+{-# LANGUAGE ViewPatterns #-}
1216
1317-- | 'Patch'es on 'Map' that can insert, delete, and move values from one key to
1418-- another
15−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
1637
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
58+
59+ -- * To
60+ , To
61+ ) where
62+
63+import Data.Coerce
64+import Data.Kind (Type)
1765import Data.Patch.Class
66+import Data.Patch.MapWithPatchingMove (PatchMapWithPatchingMove(..), To)
67+import qualified Data.Patch.MapWithPatchingMove as PM -- already a transparent synonym
1868
19−import Control.Lens hiding (from, to)
20−import Data.Align
21−import Data.Foldable
22−import Data.Function
23−import Data.List (sortBy)
69+import Control.Lens
70+import Data.List
2471import Data.Map (Map)
2572import qualified Data.Map as Map
26−import Data.Maybe
73+import Data.Proxy
2774#if !MIN_VERSION_base(4,11,0)
2875import Data.Semigroup (Semigroup (..))
2976#endif
30−import Data.Set (Set)
31−import qualified Data.Set as Set
32−import Data.These (These(..))
77+import Data.Traversable (foldMapDefault)
3378
3479-- | Patch a Map with additions, deletions, and moves. Invariant: If key @k1@
3580-- is coming from @From_Move k2@, then key @k2@ should be going to @Just k1@,
3681-- and vice versa. There should never be any unpaired From/To keys.
37−newtype PatchMapWithMove k v = PatchMapWithMove
38− { -- | Extract the internal representation of the 'PatchMapWithMove'
39− unPatchMapWithMove :: Map k (NodeInfo k v)
82+newtype PatchMapWithMove k (v :: Type) = PatchMapWithMove'
83+ { -- | Extract the underlying 'PatchMapWithPatchingMove k (Proxy v)'
84+ unPatchMapWithMove' :: PatchMapWithPatchingMove k (Proxy v)
4085 }
4186 deriving ( Show, Read, Eq, Ord
42− , Functor, Foldable, Traversable
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
4396 )
4497
45−-- | Holds the information about each key: where its new value should come from,
46−-- and where its old value should go to
47−data NodeInfo k v = NodeInfo
48− { _nodeInfo_from :: !(From k v)
49− -- ^ Where do we get the new value for this key?
50− , _nodeInfo_to :: !(To k)
51− -- ^ If the old value is being kept (i.e. moved rather than deleted or
52− -- replaced), where is it going?
53− }
54− deriving (Show, Read, Eq, Ord, Functor, Foldable, Traversable)
98+pattern Coerce :: Coercible a b => a -> b
99+pattern Coerce x <- (coerce -> x)
100+ where Coerce x = coerce x
55101
56−-- | Describe how a key's new value should be produced
57−data From k v
58− = From_Insert v -- ^ Insert the given value here
59− | From_Delete -- ^ Delete the existing value, if any, from here
60− | From_Move !k -- ^ Move the value here from the given key
61− deriving (Show, Read, Eq, Ord, Functor, Foldable, Traversable)
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))
62108
63−-- | Describe where a key's old value will go. If this is 'Just', that means
64−-- the key's old value will be moved to the given other key; if it is 'Nothing',
65−-- that means it will be deleted.
66−type To = Maybe
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
67116
68−makeWrapped ''PatchMapWithMove
117+instance Functor (PatchMapWithMove k) where
118+ fmap f = runIdentity . traverse (Identity . f)
119+
120+instance Foldable (PatchMapWithMove k) where
121+ foldMap = foldMapDefault
122+
123+instance Traversable (PatchMapWithMove k) where
124+ traverse =
125+ _PatchMapWithMove .
126+ traverse .
127+ traverse
69128
70129instance FunctorWithIndex k (PatchMapWithMove k)
71130instance FoldableWithIndex k (PatchMapWithMove k)
72131instance TraversableWithIndex k (PatchMapWithMove k) where
73132 itraverse = itraversed . Indexed
74− itraversed = _Wrapped .> itraversed <. traversed
133+ itraversed =
134+ _PatchMapWithMove .>
135+ itraversed <.
136+ traverse
75137
76138-- | Create a 'PatchMapWithMove', validating it
77139patchMapWithMove :: Ord k => Map k (NodeInfo k v) -> Maybe (PatchMapWithMove k v)
78−patchMapWithMove m = if valid then Just $ PatchMapWithMove m else Nothing
79− where valid = forwardLinks == backwardLinks
80− forwardLinks = Map.mapMaybe _nodeInfo_to m
81− backwardLinks = Map.fromList $ catMaybes $ flip fmap (Map.toList m) $ \(to, v) ->
82− case _nodeInfo_from v of
83− From_Move from -> Just (from, to)
84− _ -> Nothing
140+patchMapWithMove = fmap PatchMapWithMove' . PM.patchMapWithPatchingMove . coerce
85141
86142-- | Create a 'PatchMapWithMove' that inserts everything in the given 'Map'
87143patchMapWithMoveInsertAll :: Map k v -> PatchMapWithMove k v
88−patchMapWithMoveInsertAll m = PatchMapWithMove $ flip fmap m $ \v -> NodeInfo
89− { _nodeInfo_from = From_Insert v
90− , _nodeInfo_to = Nothing
91− }
144+patchMapWithMoveInsertAll = PatchMapWithMove' . PM.patchMapWithPatchingMoveInsertAll
92145
93146-- | Make a @'PatchMapWithMove' k v@ which has the effect of inserting or updating a value @v@ to the given key @k@, like 'Map.insert'.
94147insertMapKey :: k -> v -> PatchMapWithMove k v
95−insertMapKey k v = PatchMapWithMove . Map.singleton k $ NodeInfo (From_Insert v) Nothing
148+insertMapKey k v = PatchMapWithMove' $ PM.insertMapKey k v
96149
97150-- |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:
98151--
@@ -100,188 +153,160 @@ insertMapKey k v = PatchMapWithMove . Map.singleton k $ NodeInfo (From_Insert v)
100153-- 'Map.delete' src (maybe map ('Map.insert' dst) (Map.lookup src map))
101154-- @
102155moveMapKey :: Ord k => k -> k -> PatchMapWithMove k v
103−moveMapKey src dst
104− | src == dst = mempty
105− | otherwise =
106− PatchMapWithMove $ Map.fromList
107− [ (dst, NodeInfo (From_Move src) Nothing)
108− , (src, NodeInfo From_Delete (Just dst))
109− ]
156+moveMapKey src dst = PatchMapWithMove' $ PM.moveMapKey src dst
110157
111158-- |Make a @'PatchMapWithMove' k v@ which has the effect of swapping two keys in the mapping, equivalent to:
112159--
113160-- @
114161-- let aMay = Map.lookup a map
115162-- bMay = Map.lookup b map
116−-- in maybe id (Map.insert a) (bMay `mplus` aMay)
117−-- . 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)
118165-- . Map.delete a . Map.delete b $ map
119166-- @
120167swapMapKey :: Ord k => k -> k -> PatchMapWithMove k v
121−swapMapKey src dst
122− | src == dst = mempty
123− | otherwise =
124− PatchMapWithMove $ Map.fromList
125− [ (dst, NodeInfo (From_Move src) (Just src))
126− , (src, NodeInfo (From_Move dst) (Just dst))
127− ]
168+swapMapKey src dst = PatchMapWithMove' $ PM.swapMapKey src dst
128169
129170-- |Make a @'PatchMapWithMove' k v@ which has the effect of deleting a key in the mapping, equivalent to 'Map.delete'.
130171deleteMapKey :: k -> PatchMapWithMove k v
131−deleteMapKey k = PatchMapWithMove . Map.singleton k $ NodeInfo From_Delete Nothing
172+deleteMapKey = PatchMapWithMove' . PM.deleteMapKey
132173
133174-- | Wrap a @'Map' k (NodeInfo k v)@ representing patch changes into a @'PatchMapWithMove' k v@, without checking any invariants.
134175--
135176-- __Warning:__ when using this function, you must ensure that the invariants of 'PatchMapWithMove' are preserved; they will not be checked.
136177unsafePatchMapWithMove :: Map k (NodeInfo k v) -> PatchMapWithMove k v
137−unsafePatchMapWithMove = PatchMapWithMove
178+unsafePatchMapWithMove = coerce PM.unsafePatchMapWithPatchingMove
138179
139180-- | Apply the insertions, deletions, and moves to a given 'Map'
140181instance Ord k => Patch (PatchMapWithMove k v) where
141182 type PatchTarget (PatchMapWithMove k v) = Map k v
142− apply (PatchMapWithMove p) 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?
143− where insertions = flip Map.mapMaybeWithKey p $ \_ ni -> case _nodeInfo_from ni of
144− From_Insert v -> Just v
145− From_Move k -> Map.lookup k old
146− From_Delete -> Nothing
147− deletions = flip Map.mapMaybeWithKey p $ \_ ni -> case _nodeInfo_from ni of
148− From_Delete -> Just ()
149− _ -> Nothing
183+ apply (PatchMapWithMove' p) = apply p
150184
151185-- | Returns all the new elements that will be added to the 'Map'.
152186patchMapWithMoveNewElements :: PatchMapWithMove k v -> [v]
153−patchMapWithMoveNewElements = Map.elems . patchMapWithMoveNewElementsMap
187+patchMapWithMoveNewElements = PM.patchMapWithPatchingMoveNewElements . unPatchMapWithMove'
154188
155189-- | Return a @'Map' k v@ with all the inserts/updates from the given @'PatchMapWithMove' k v@.
156190patchMapWithMoveNewElementsMap :: PatchMapWithMove k v -> Map k v
157−patchMapWithMoveNewElementsMap (PatchMapWithMove p) = Map.mapMaybe f p
158− where f ni = case _nodeInfo_from ni of
159− From_Insert v -> Just v
160− From_Move _ -> Nothing
161− From_Delete -> Nothing
191+patchMapWithMoveNewElementsMap = PM.patchMapWithPatchingMoveNewElementsMap . unPatchMapWithMove'
162192
163193-- | Create a 'PatchMapWithMove' that, if applied to the given 'Map', will sort
164194-- its values using the given ordering function. The set keys of the 'Map' is
165195-- not changed.
166196patchThatSortsMapWith :: Ord k => (v -> v -> Ordering) -> Map k v -> PatchMapWithMove k v
167−patchThatSortsMapWith cmp m = PatchMapWithMove $ Map.fromList $ catMaybes $ zipWith g unsorted sorted
168− where unsorted = Map.toList m
169− sorted = sortBy (cmp `on` snd) unsorted
170− f (to, _) (from, _) = if to == from then Nothing else
171− Just (from, to)
172− reverseMapping = Map.fromList $ catMaybes $ zipWith f unsorted sorted
173− g (to, _) (from, _) = if to == from then Nothing else
174− let Just movingTo = Map.lookup to reverseMapping
175− in Just (to, NodeInfo (From_Move from) $ Just movingTo)
197+patchThatSortsMapWith cmp = PatchMapWithMove' . PM.patchThatSortsMapWith cmp
176198
177199-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
178200-- will produce a 'Map' with the same values as the second 'Map' but with the
179201-- values sorted with the given ordering function.
180−patchThatChangesAndSortsMapWith :: forall k v. (Ord k, Ord v) => (v -> v -> Ordering) -> Map k v -> Map k v -> PatchMapWithMove k v
202+patchThatChangesAndSortsMapWith :: (Ord k, Ord v) => (v -> v -> Ordering) -> Map k v -> Map k v -> PatchMapWithMove k v
181203patchThatChangesAndSortsMapWith cmp oldByIndex newByIndexUnsorted = patchThatChangesMap oldByIndex newByIndex
182204 where newList = Map.toList newByIndexUnsorted
183205 newByIndex = Map.fromList $ zip (fst <$> newList) $ sortBy cmp $ snd <$> newList
184206
185207-- | Create a 'PatchMapWithMove' that, if applied to the first 'Map' provided,
186208-- will produce the second 'Map'.
187−patchThatChangesMap :: forall k v. (Ord k, Ord v) => Map k v -> Map k v -> PatchMapWithMove k v
188−patchThatChangesMap oldByIndex newByIndex = patch
189− where invert :: Map k v -> Map v (Set k)
190− invert = Map.fromListWith (<>) . fmap (\(k, v) -> (v, Set.singleton k)) . Map.toList
191− -- In the places where we use unionDistinct, a non-distinct key indicates a bug in this function
192− unionDistinct :: forall k' v'. Ord k' => Map k' v' -> Map k' v' -> Map k' v'
193− unionDistinct = Map.unionWith (error "patchThatChangesMap: non-distinct keys")
194− unionPairDistinct :: (Map k (From k v), Map k (To k)) -> (Map k (From k v), Map k (To k)) -> (Map k (From k v), Map k (To k))
195− unionPairDistinct (oldFroms, oldTos) (newFroms, newTos) = (unionDistinct oldFroms newFroms, unionDistinct oldTos newTos)
196− -- Generate patch info for a single value
197− -- Keys that are found in both the old and new sets will not be patched
198− -- Keys that are found in only the old set will be moved to a new position if any are available; otherwise they will be deleted
199− -- Keys that are found in only the new set will be populated by moving an old key if any are available; otherwise they will be inserted
200− patchSingleValue :: v -> Set k -> Set k -> (Map k (From k v), Map k (To k))
201− patchSingleValue v oldKeys newKeys = foldl' unionPairDistinct mempty $ align (toList $ oldKeys `Set.difference` newKeys) (toList $ newKeys `Set.difference` oldKeys) <&> \case
202− This oldK -> (mempty, Map.singleton oldK Nothing) -- There's nowhere for this value to go, so we know we are deleting it
203− That newK -> (Map.singleton newK $ From_Insert v, mempty) -- There's nowhere fo this value to come from, so we know we are inserting it
204− These oldK newK -> (Map.singleton newK $ From_Move oldK, Map.singleton oldK $ Just newK)
205− -- Run patchSingleValue on a These. Missing old or new sets are considered empty
206− patchSingleValueThese :: v -> These (Set k) (Set k) -> (Map k (From k v), Map k (To k))
207− patchSingleValueThese v = \case
208− This oldKeys -> patchSingleValue v oldKeys mempty
209− That newKeys -> patchSingleValue v mempty newKeys
210− These oldKeys newKeys -> patchSingleValue v oldKeys newKeys
211− -- Generate froms and tos for all values, then merge them together
212− (froms, tos) = foldl' unionPairDistinct mempty $ Map.mapWithKey patchSingleValueThese $ align (invert oldByIndex) (invert newByIndex)
213− patch = unsafePatchMapWithMove $ align froms tos <&> \case
214− This from -> NodeInfo from Nothing -- Since we don't have a 'to' record for this key, that must mean it isn't being moved anywhere, so it should be deleted.
215− That to -> NodeInfo From_Delete to -- Since we don't have a 'from' record for this key, it must be getting deleted
216− These from to -> NodeInfo from to
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
217261
218262-- | Change the 'From' value of a 'NodeInfo'
219263nodeInfoMapFrom :: (From k v -> From k v) -> NodeInfo k v -> NodeInfo k v
220−nodeInfoMapFrom f ni = ni { _nodeInfo_from = f $ _nodeInfo_from ni }
264+nodeInfoMapFrom f = coerce $ PM.nodeInfoMapFrom (unFrom' . f . From')
221265
222266-- | Change the 'From' value of a 'NodeInfo', using a 'Functor' (or
223267-- 'Applicative', 'Monad', etc.) action to get the new value
224−nodeInfoMapMFrom :: Functor f => (From k v -> f (From k v)) -> NodeInfo k v -> f (NodeInfo k v)
225−nodeInfoMapMFrom f ni = fmap (\result -> ni { _nodeInfo_from = result }) $ f $ _nodeInfo_from ni
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
226275
227276-- | Set the 'To' field of a 'NodeInfo'
228277nodeInfoSetTo :: To k -> NodeInfo k v -> NodeInfo k v
229−nodeInfoSetTo to ni = ni { _nodeInfo_to = to }
230−
231−-- |Helper data structure used for composing patches using the monoid instance.
232−data Fixup k v
233− = Fixup_Delete
234− | Fixup_Update (These (From k v) (To k))
235−
236−-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
237−instance Ord k => Semigroup (PatchMapWithMove k v) where
238− PatchMapWithMove ma <> PatchMapWithMove mb = PatchMapWithMove m
239− where
240− connections = Map.toList $ Map.intersectionWithKey (\_ a b -> (_nodeInfo_to a, _nodeInfo_from b)) ma mb
241− h :: (k, (Maybe k, From k v)) -> [(k, Fixup k v)]
242− h (_, (mToAfter, editBefore)) = case (mToAfter, editBefore) of
243− (Just toAfter, From_Move fromBefore)
244− | fromBefore == toAfter
245− -> [(toAfter, Fixup_Delete)]
246− | otherwise
247− -> [ (toAfter, Fixup_Update (This editBefore))
248− , (fromBefore, Fixup_Update (That mToAfter))
249− ]
250− (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
251− (Just toAfter, _) -> [(toAfter, Fixup_Update (This editBefore))]
252− (Nothing, _) -> []
253− mergeFixups _ Fixup_Delete Fixup_Delete = Fixup_Delete
254− mergeFixups _ (Fixup_Update a) (Fixup_Update b)
255− | This x <- a, That y <- b
256− = Fixup_Update $ These x y
257− | That y <- a, This x <- b
258− = Fixup_Update $ These x y
259− mergeFixups _ _ _ = error "PatchMapWithMove: incompatible fixups"
260− fixups = Map.fromListWithKey mergeFixups $ concatMap h connections
261− combineNodeInfos _ nia nib = NodeInfo
262− { _nodeInfo_from = _nodeInfo_from nia
263− , _nodeInfo_to = _nodeInfo_to nib
264− }
265− applyFixup _ ni = \case
266− Fixup_Delete -> Nothing
267− Fixup_Update u -> Just $ NodeInfo
268− { _nodeInfo_from = fromMaybe (_nodeInfo_from ni) $ getHere u
269− , _nodeInfo_to = fromMaybe (_nodeInfo_to ni) $ getThere u
270− }
271− m = Map.differenceWithKey applyFixup (Map.unionWithKey combineNodeInfos ma mb) fixups
272− getHere :: These a b -> Maybe a
273− getHere = \case
274− This a -> Just a
275− These a _ -> Just a
276− That _ -> Nothing
277− getThere :: These a b -> Maybe b
278− getThere = \case
279− This _ -> Nothing
280− These _ b -> Just b
281− That b -> Just b
282−
283−--TODO: Figure out how to implement this in terms of PatchDMapWithMove rather than duplicating it here
284−-- |Compose patches having the same effect as applying the patches in turn: @'applyAlways' (p <> q) == 'applyAlways' p . 'applyAlways' q@
285−instance Ord k => Monoid (PatchMapWithMove k v) where
286− mempty = PatchMapWithMove mempty
287− mappend = (<>)
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