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# 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.each_with_object({}) { |tag, h| h[tag.id] = tag }
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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