- # frozen_string_literal: true
-
- class TrendingTags
- KEY = 'trending_tags'
- EXPIRE_HISTORY_AFTER = 7.days.seconds
- EXPIRE_TRENDS_AFTER = 1.day.seconds
- THRESHOLD = 5
- LIMIT = 10
- REVIEW_THRESHOLD = 3
- MAX_SCORE_COOLDOWN = 2.days.freeze
- MAX_SCORE_HALFLIFE = 2.hours.freeze
-
- class << self
- include Redisable
-
- def record_use!(tag, account, at_time = Time.now.utc)
- return if account.silenced? || account.bot? || !tag.usable? || !(tag.trendable? || tag.requires_review?)
-
- increment_historical_use!(tag.id, at_time)
- increment_unique_use!(tag.id, account.id, at_time)
- increment_use!(tag.id, at_time)
-
- tag.update(last_status_at: Time.now.utc) if tag.last_status_at.nil? || tag.last_status_at < 12.hours.ago
- end
-
- def update!(at_time = Time.now.utc)
- tag_ids = redis.smembers("#{KEY}:used:#{at_time.beginning_of_day.to_i}") + redis.zrange(KEY, 0, -1)
- tags = Tag.where(id: tag_ids.uniq)
-
- # First pass to calculate scores and update the set
-
- tags.each do |tag|
- expected = redis.pfcount("activity:tags:#{tag.id}:#{(at_time - 1.day).beginning_of_day.to_i}:accounts").to_f
- expected = 1.0 if expected.zero?
- observed = redis.pfcount("activity:tags:#{tag.id}:#{at_time.beginning_of_day.to_i}:accounts").to_f
- max_time = tag.max_score_at
- max_score = tag.max_score
- max_score = 0 if max_time.nil? || max_time < (at_time - MAX_SCORE_COOLDOWN)
-
- score = begin
- if expected > observed || observed < THRESHOLD
- 0
- else
- ((observed - expected)**2) / expected
- end
- end
-
- if score > max_score
- max_score = score
- max_time = at_time
-
- # Not interested in triggering any callbacks for this
- tag.update_columns(max_score: max_score, max_score_at: max_time)
- end
-
- decaying_score = max_score * (0.5**((at_time.to_f - max_time.to_f) / MAX_SCORE_HALFLIFE.to_f))
-
- if decaying_score.zero?
- redis.zrem(KEY, tag.id)
- else
- redis.zadd(KEY, decaying_score, tag.id)
- end
- end
-
- users_for_review = User.staff.includes(:account).to_a.select(&:allows_trending_tag_emails?)
-
- # Second pass to notify about previously unreviewed trends
-
- tags.each do |tag|
- current_rank = redis.zrevrank(KEY, tag.id)
- needs_review_notification = tag.requires_review? && !tag.requested_review?
- rank_passes_threshold = current_rank.present? && current_rank <= REVIEW_THRESHOLD
-
- next unless !tag.trendable? && rank_passes_threshold && needs_review_notification
-
- tag.touch(:requested_review_at)
-
- users_for_review.each do |user|
- AdminMailer.new_trending_tag(user.account, tag).deliver_later!
- end
- end
-
- # Trim older items
-
- redis.zremrangebyrank(KEY, 0, -(LIMIT + 1))
- redis.zremrangebyscore(KEY, '(0.3', '-inf')
- end
-
- def get(limit, filtered: true)
- tag_ids = redis.zrevrange(KEY, 0, LIMIT - 1).map(&:to_i)
-
- tags = Tag.where(id: tag_ids)
- tags = tags.trendable if filtered
- tags = tags.index_by(&:id)
-
- tag_ids.map { |tag_id| tags[tag_id] }.compact.take(limit)
- end
-
- def trending?(tag)
- rank = redis.zrevrank(KEY, tag.id)
- rank.present? && rank < LIMIT
- end
-
- private
-
- def increment_historical_use!(tag_id, at_time)
- key = "activity:tags:#{tag_id}:#{at_time.beginning_of_day.to_i}"
- redis.incrby(key, 1)
- redis.expire(key, EXPIRE_HISTORY_AFTER)
- end
-
- def increment_unique_use!(tag_id, account_id, at_time)
- key = "activity:tags:#{tag_id}:#{at_time.beginning_of_day.to_i}:accounts"
- redis.pfadd(key, account_id)
- redis.expire(key, EXPIRE_HISTORY_AFTER)
- end
-
- def increment_use!(tag_id, at_time)
- key = "#{KEY}:used:#{at_time.beginning_of_day.to_i}"
- redis.sadd(key, tag_id)
- redis.expire(key, EXPIRE_HISTORY_AFTER)
- end
- end
- end
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