Prevent duplication of mention on post update

and delete mentions and notifications of user no longer mentioned

plume-models/src/mentions.rs

@@ -102,6 +102,12 @@ impl Mention {
             })
         }
     }
+
+    pub fn delete(&self, conn: &Connection) {
+        //find related notifications and delete them
+        Notification::find(conn, notification_kind::MENTION, self.id).map(|n| n.delete(conn));
+        diesel::delete(self).execute(conn).expect("Mention::delete: mention deletion error");
+    }
 }
 
 impl Notify<Connection> for Mention {

plume-models/src/notifications.rs

@@ -106,4 +106,8 @@ impl Notification {
         });
         json
     }
+
+    pub fn delete(&self, conn: &Connection) {
+        diesel::delete(self).execute(conn).expect("Notification::delete: notification deletion error");
+    }
 }

src/routes/posts.rs

@@ -210,8 +210,15 @@ fn update(blog: String, slug: String, user: User, conn: DbConn, data: LenientFor
             let post = post.update_ap_url(&*conn);
 
             if post.published {
-                for m in mentions.into_iter() {
+                let old_mentions = Mention::list_for_post(&conn, post.id);
-                    Mention::from_activity(&*conn, Mention::build_activity(&*conn, m), post.id, true, true);
+                let old_user_mentioned = old_mentions.iter()
+                    .filter_map(|m| User::get(&conn, m.mentioned_id).map(|u| u.get_fqn(&conn)))
+                    .collect::<HashSet<_>>();
+                for m in mentions.difference(&old_user_mentioned).into_iter() {
+                    Mention::from_activity(&*conn, Mention::build_activity(&*conn, m.clone()), post.id, true, true);
+                }
+                for m in old_mentions.iter().filter(|m| !User::get(&conn, m.mentioned_id).map(|u| mentions.contains(&u.get_fqn(&conn))).unwrap_or(false)) {
+                    m.delete(&conn);
                 }
             }