try delete follower too

app/DB.hs

@@ -17,6 +17,7 @@ data DB
   , getNote :: DB.Int64 -> IO (Maybe Note)
   , insertNote :: NoteEntry -> IO (DB.Int64, Note)
   , insertFollower :: FollowerEntry -> IO DB.Int64
+  , deleteFollower :: FollowerEntry -> IO DB.Int64
   , getFollowers :: IO [Follower]
   }
 
@@ -61,6 +62,8 @@ mkDB connstr details = do
           \note -> DB.withPool pool (insertNoteToDb (actorUrl details) note)
       , insertFollower =
           \follower -> DB.withPool pool (insertFollowerToDb follower)
+      , deleteFollower =
+          \follower -> DB.withPool pool (deleteFollowerFromDb follower)
       , getFollowers =
           DB.withPool pool (getFollowersFromDb $ actorUrl details)
       }
@@ -139,6 +142,11 @@ insertFollowerToDb follower = do
   [n] <- map decodeIntRow <$> uncurry DB.runWith (insertFollowerSQL follower)
   pure n
 
+deleteFollowerFromDb :: FollowerEntry -> DB.SQLite DB.Int64
+deleteFollowerFromDb follower = do
+  [n] <- map decodeIntRow <$> uncurry DB.runWith (deleteFollowerSQL follower)
+  pure n
+
 getFollowersFromDb :: Url -> DB.SQLite [Follower]
 getFollowersFromDb url =
   map decodeFollowerRow <$> uncurry DB.runWith (getFollowersSQL url)
@@ -211,7 +219,7 @@ insertNoteSQL actor note =
 insertFollowerSQL :: FollowerEntry -> (DB.SQL, [DB.SQLData])
 insertFollowerSQL follower =
   ( [r|
-      INSERT INTO note(follow_id, actor)
+      INSERT INTO follower(follow_id, actor)
       VALUES (?, ?)
       RETURNING id
     |]
@@ -221,6 +229,19 @@ insertFollowerSQL follower =
     ]
   )
 
+deleteFollowerSQL :: FollowerEntry -> (DB.SQL, [DB.SQLData])
+deleteFollowerSQL follower =
+  ( [r|
+      DELETE FROM follower
+      WHERE followId = ? AND actor = ?
+      RETURNING followId
+    |]
+  ,
+    [ DB.SQLText follower.followId
+    , DB.SQLText follower.actorId
+    ]
+  )
+
 getFollowersSQL :: Url -> (DB.SQL, [DB.SQLData])
 getFollowersSQL url =
   ( [r|

app/Routes.hs

@@ -150,6 +150,32 @@ handleInbox db detailsFile activity = do
             else Twain.next
         Nothing ->
           Twain.next
+    Fedi.ActivityUndo
+      ( Fedi.Object
+        { otype = Fedi.TypeActivity
+          { atype = Fedi.TypeUndo
+            { object = Fedi.ActivityFollow follow
+            }
+          }
+        }) -> do
+      let
+        id' = follow.id
+        actor = follow.otype.actor
+        object = follow.otype.atype.object
+      case id' of
+        Just id'' -> do
+          if object == Fedi.LLink (Fedi.Link $ Fedi.actorUrl details)
+            then do
+              liftIO do
+                deletedId <- db.deleteFollower FollowerEntry
+                  { actorId = fromString actor.unwrap
+                  , followId = fromString id''.unwrap
+                  }
+                print ("deleted follower: " <> show deletedId)
+                pure $ Fedi.jsonLD "{}"
+            else Twain.next
+        Nothing ->
+          Twain.next
     _ -> do
       liftIO (print activity)
       Twain.next

src/Fedi/Types.hs

@@ -322,6 +322,30 @@ instance A.FromJSON TypeFollow where
       object <- value A..: "object"
       pure TypeFollow {..}
 
+-- | Undo
+type Undo = Activity TypeUndo
+
+data TypeUndo
+  = TypeUndo
+  { object :: AnyActivity
+  }
+  deriving (Show, Eq)
+
+instance ToObject TypeUndo where
+  toObject undo =
+    [ "type" A..= ("Undo" :: String)
+    , "object" A..= undo.object
+    ]
+
+instance A.FromJSON TypeUndo where
+  parseJSON =
+    A.withObject "TypeUndo" \value -> do
+      typ :: String <- value A..: "type"
+      guard (typ == "Undo")
+      object <- value A..: "object"
+      pure TypeUndo {..}
+
+
 --
 type Like = Object (TypeActivity TypeLike)
 
@@ -342,6 +366,7 @@ instance A.FromJSON TypeLike where
 data AnyActivity
   = -- ActivityAnnounce Announce
     ActivityCreate Create
+  | ActivityUndo Undo
   | ActivityFollow Follow
   | --  | ActivityLike Like
     ActivityAccept Accept
@@ -352,6 +377,7 @@ instance A.ToJSON AnyActivity where
   toJSON = \case
     --    ActivityAnnounce obj -> A.toJSON obj
     ActivityCreate obj -> A.toJSON obj
+    ActivityUndo obj -> A.toJSON obj
     ActivityFollow obj -> A.toJSON obj
     --    ActivityLike obj -> A.toJSON obj
     ActivityAccept obj -> A.toJSON obj
@@ -363,6 +389,7 @@ instance A.FromJSON AnyActivity where
       typ :: String <- v A..: "type"
       case typ of
         "Create" -> ActivityCreate <$> A.parseJSON value
+        "Undo" -> ActivityUndo <$> A.parseJSON value
         "Follow" -> ActivityFollow <$> A.parseJSON value
         "Accept" -> ActivityAccept <$> A.parseJSON value
         "Reject" -> ActivityReject <$> A.parseJSON value