about summary refs log tree commit diff
path: root/app/lib/feed_manager.rb
blob: 6398aa6d66a04307ace2c0716352f6ca47de1e33 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
# frozen_string_literal: true

require 'singleton'

class FeedManager
  include Singleton

  MAX_ITEMS = 400

  # 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)
    if timeline_type == :home
      filter_from_home?(status, receiver_id)
    elsif timeline_type == :mentions
      filter_from_mentions?(status, receiver_id)
    else
      false
    end
  end

  def push(timeline_type, account, status)
    return false unless add_to_feed(timeline_type, account, status)

    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)
    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)
    timeline_type != :home || redis.get("subscribed:timeline:#{account_id}").present?
  end

  def merge_into_timeline(from_account, into_account)
    timeline_key = key(:home, into_account.id)
    query        = from_account.statuses.limit(FeedManager::MAX_ITEMS / 4)

    if redis.zcard(timeline_key) >= FeedManager::MAX_ITEMS / 4
      oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true)&.first&.last&.to_i || 0
      query = query.where('id > ?', oldest_home_score)
    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)
  end

  def unmerge_from_timeline(from_account, into_account)
    timeline_key = key(:home, into_account.id)
    oldest_home_score = redis.zrange(timeline_key, 0, 0, with_scores: true)&.first&.last&.to_i || 0

    from_account.statuses.select('id, reblog_of_id').where('id > ?', oldest_home_score).reorder(nil).find_each do |status|
      unpush(:home, into_account, status)
    end
  end

  def clear_from_timeline(account, target_account)
    timeline_key = key(:home, account.id)
    timeline_status_ids = redis.zrange(timeline_key, 0, -1)
    target_statuses = Status.where(id: timeline_status_ids, account: target_account)

    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

  def redis
    Redis.current
  end

  def filter_from_home?(status, receiver_id)
    return true if status.reply? && (status.in_reply_to_id.nil? || status.in_reply_to_account_id.nil?)

    check_for_mutes = [status.account_id]
    check_for_mutes.concat([status.reblog.account_id]) if status.reblog?

    return true if Mute.where(account_id: receiver_id, target_account_id: check_for_mutes).any?

    check_for_blocks = status.mentions.pluck(:account_id)
    check_for_blocks.concat([status.reblog.account_id]) if status.reblog?

    return true if Block.where(account_id: receiver_id, target_account_id: check_for_blocks).any?

    if status.reply? && !status.in_reply_to_account_id.nil?                                                              # Filter out if it's a reply
      should_filter   = !Follow.where(account_id: receiver_id, target_account_id: status.in_reply_to_account_id).exists? # and I'm not following the person it's a reply to
      should_filter &&= receiver_id != status.in_reply_to_account_id                                                     # and it's not a reply to me
      should_filter &&= status.account_id != status.in_reply_to_account_id                                               # and it's not a self-reply
      return should_filter
    elsif status.reblog?                                                                                                 # Filter out a reblog
      should_filter   = Block.where(account_id: status.reblog.account_id, target_account_id: receiver_id).exists?        # or if the author of the reblogged status is blocking me
      should_filter ||= AccountDomainBlock.where(account_id: receiver_id, domain: status.reblog.account.domain).exists?  # or the author's domain is blocked
      return should_filter
    end

    false
  end

  def filter_from_mentions?(status, receiver_id)
    return true if receiver_id == status.account_id

    check_for_blocks = [status.account_id]
    check_for_blocks.concat(status.mentions.pluck(:account_id))
    check_for_blocks.concat([status.in_reply_to_account]) if status.reply? && !status.in_reply_to_account_id.nil?

    should_filter   = Block.where(account_id: receiver_id, target_account_id: check_for_blocks).any?                                     # Filter if it's from someone I blocked, in reply to someone I blocked, or mentioning someone I blocked
    should_filter ||= (status.account.silenced? && !Follow.where(account_id: receiver_id, target_account_id: status.account_id).exists?) # of if the account is silenced and I'm not following them

    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