1 files changed, 103 insertions, 25 deletions
diff --git a/app/lib/feed_manager.rb b/app/lib/feed_manager.rb
index b1ae11084..c509c5702 100644
--- a/app/lib/feed_manager.rb
+++ b/app/lib/feed_manager.rb
@@ -7,8 +7,13 @@ class FeedManager
 
   MAX_ITEMS = 400
 
-  def key(type, id)
-    "feed:#{type}:#{id}"
+  # Must be <= MAX_ITEMS or the tracking sets will grow forever
+  REBLOG_FALLOFF = 40
+
+  def key(type, id, subtype = nil)
+    return "feed:#{type}:#{id}" unless subtype
+
+    "feed:#{type}:#{id}:#{subtype}"
   end
 
   def filter?(timeline_type, status, receiver_id)
@@ -22,23 +27,36 @@ class FeedManager
   end
 
   def push(timeline_type, account, status)
-    timeline_key = key(timeline_type, account.id)
+    return false unless add_to_feed(timeline_type, account, status)
 
-    if status.reblog?
-      # If the original status is within 40 statuses from top, do not re-insert it into the feed
-      rank = redis.zrevrank(timeline_key, status.reblog_of_id)
-      return if !rank.nil? && rank < 40
-      redis.zadd(timeline_key, status.id, status.reblog_of_id)
-    else
-      redis.zadd(timeline_key, status.id, status.id)
-      trim(timeline_type, account.id)
-    end
+    trim(timeline_type, account.id)
 
     PushUpdateWorker.perform_async(account.id, status.id) if push_update_required?(timeline_type, account.id)
+
+    true
+  end
+
+  def unpush(timeline_type, account, status)
+    return false unless remove_from_feed(timeline_type, account, status)
+
+    payload = Oj.dump(event: :delete, payload: status.id.to_s)
+    Redis.current.publish("timeline:#{account.id}", payload)
+
+    true
   end
 
   def trim(type, account_id)
-    redis.zremrangebyrank(key(type, account_id), '0', (-(FeedManager::MAX_ITEMS + 1)).to_s)
+    timeline_key = key(type, account_id)
+    reblog_key = key(type, account_id, 'reblogs')
+    # Remove any items past the MAX_ITEMS'th entry in our feed
+    redis.zremrangebyrank(timeline_key, '0', (-(FeedManager::MAX_ITEMS + 1)).to_s)
+
+    # Get the score of the REBLOG_FALLOFF'th item in our feed, and stop
+    # tracking anything after it for deduplication purposes.
+    falloff_rank = FeedManager::REBLOG_FALLOFF - 1
+    falloff_range = redis.zrevrange(timeline_key, falloff_rank, falloff_rank, with_scores: true)
+    falloff_score = falloff_range&.first&.last&.to_i || 0
+    redis.zremrangebyscore(reblog_key, 0, falloff_score)
   end
 
   def push_update_required?(timeline_type, account_id)
@@ -54,11 +72,9 @@ class FeedManager
       query = query.where('id > ?', oldest_home_score)
     end
 
-    redis.pipelined do
-      query.each do |status|
-        next if status.direct_visibility? || filter?(:home, status, into_account)
-        redis.zadd(timeline_key, status.id, status.id)
-      end
+    query.each do |status|
+      next if status.direct_visibility? || filter?(:home, status, into_account)
+      add_to_feed(:home, into_account, status)
     end
 
     trim(:home, into_account.id)
@@ -69,11 +85,8 @@ class FeedManager
     oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true)&.first&.last&.to_i || 0
 
     from_account.statuses.select('id').where('id > ?', oldest_home_score).reorder(nil).find_in_batches do |statuses|
-      redis.pipelined do
-        statuses.each do |status|
-          redis.zrem(timeline_key, status.id)
-          redis.zremrangebyscore(timeline_key, status.id, status.id)
-        end
+      statuses.each do |status|
+        unpush(:home, into_account, status)
       end
     end
   end
@@ -81,9 +94,20 @@ class FeedManager
   def clear_from_timeline(account, target_account)
     timeline_key = key(:home, account.id)
     timeline_status_ids = redis.zrange(timeline_key, 0, -1)
-    target_status_ids = Status.where(id: timeline_status_ids, account: target_account).ids
+    target_statuses = Status.where(id: timeline_status_ids, account: target_account)
 
-    redis.zrem(timeline_key, target_status_ids) if target_status_ids.present?
+    target_statuses.each do |status|
+      unpush(:home, account, status)
+    end
+  end
+
+  def populate_feed(account)
+    prepopulate_limit = FeedManager::MAX_ITEMS / 4
+    statuses = Status.as_home_timeline(account).order(account_id: :desc).limit(prepopulate_limit)
+    statuses.reverse_each do |status|
+      next if filter_from_home?(status, account)
+      add_to_feed(:home, account, status)
+    end
   end
 
   private
@@ -131,4 +155,58 @@ class FeedManager
 
     should_filter
   end
+
+  # Adds a status to an account's feed, returning true if a status was
+  # added, and false if it was not added to the feed. Note that this is
+  # an internal helper: callers must call trim or push updates if
+  # either action is appropriate.
+  def add_to_feed(timeline_type, account, status)
+    timeline_key = key(timeline_type, account.id)
+    reblog_key = key(timeline_type, account.id, 'reblogs')
+
+    if status.reblog?
+      # If the original status or a reblog of it is within
+      # REBLOG_FALLOFF statuses from the top, do not re-insert it into
+      # the feed
+      rank = redis.zrevrank(timeline_key, status.reblog_of_id)
+      return false if !rank.nil? && rank < FeedManager::REBLOG_FALLOFF
+
+      reblog_rank = redis.zrevrank(reblog_key, status.reblog_of_id)
+      return false unless reblog_rank.nil?
+
+      redis.zadd(timeline_key, status.id, status.id)
+      redis.zadd(reblog_key, status.id, status.reblog_of_id)
+    else
+      redis.zadd(timeline_key, status.id, status.id)
+    end
+
+    true
+  end
+
+  # Removes an individual status from a feed, correctly handling cases
+  # with reblogs, and returning true if a status was removed. As with
+  # `add_to_feed`, this does not trigger push updates, so callers must
+  # do so if appropriate.
+  def remove_from_feed(timeline_type, account, status)
+    timeline_key = key(timeline_type, account.id)
+    reblog_key = key(timeline_type, account.id, 'reblogs')
+
+    if status.reblog?
+      # 1. If the reblogging status is not in the feed, stop.
+      status_rank = redis.zrevrank(timeline_key, status.id)
+      return false if status_rank.nil?
+
+      # 2. Remove the reblogged status from the `:reblogs` zset.
+      redis.zrem(reblog_key, status.reblog_of_id)
+
+      # 3. Add the reblogged status to the feed using the reblogging
+      # status' ID as its score, and the reblogged status' ID as its
+      # value.
+      redis.zadd(timeline_key, status.id, status.reblog_of_id)
+
+      # 4. Remove the reblogging status from the feed (as normal)
+    end
+
+    redis.zrem(timeline_key, status.id)
+  end
 end