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# frozen_string_literal: true
class Trends::Tags < Trends::Base
PREFIX = 'trending_tags'
# Minimum amount of uses by unique accounts to begin calculating the score
THRESHOLD = 15
# Minimum rank (lower = better) before requesting a review
REVIEW_THRESHOLD = 10
# For this amount of time, the peak score (if bigger than current score) is decayed-from
MAX_SCORE_COOLDOWN = 2.days.freeze
# How quickly a peak score decays
MAX_SCORE_HALFLIFE = 4.hours.freeze
def register(status, at_time = Time.now.utc)
original_status = status.reblog? ? status.reblog : status
return unless original_status.public_visibility? && status.public_visibility? &&
!original_status.account.silenced? && !status.account.silenced?
original_status.tags.each do |tag|
add(tag, status.account_id, at_time) if tag.usable?
end
end
def add(tag, account_id, at_time = Time.now.utc)
tag.history.add(account_id, at_time)
record_used_id(tag.id, at_time)
end
def refresh(at_time = Time.now.utc)
tags = Tag.where(id: (recently_used_ids(at_time) + currently_trending_ids(false, -1)).uniq)
calculate_scores(tags, at_time)
trim_older_items
end
def get(allowed, limit)
tag_ids = currently_trending_ids(allowed, limit)
tags = Tag.where(id: tag_ids).index_by(&:id)
tag_ids.map { |id| tags[id] }.compact
end
def request_review
tags = Tag.where(id: currently_trending_ids(false, -1))
tags_requiring_review = tags.filter_map do |tag|
next unless would_be_trending?(tag.id) && !tag.trendable? && tag.requires_review_notification?
tag.touch(:requested_review_at)
tag
end
return if tags_requiring_review.empty?
User.staff.includes(:account).find_each do |user|
AdminMailer.new_trending_tags(user.account, tags_requiring_review).deliver_later! if user.allows_trending_tag_emails?
end
end
protected
def key_prefix
PREFIX
end
private
def calculate_scores(tags, at_time)
tags.each do |tag|
expected = tag.history.get(at_time - 1.day).accounts.to_f
expected = 1.0 if expected.zero?
observed = tag.history.get(at_time).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("#{PREFIX}:all", tag.id)
redis.zrem("#{PREFIX}:allowed", tag.id)
else
redis.zadd("#{PREFIX}:all", decaying_score, tag.id)
if tag.trendable?
redis.zadd("#{PREFIX}:allowed", decaying_score, tag.id)
else
redis.zrem("#{PREFIX}:allowed", tag.id)
end
end
end
end
def would_be_trending?(id)
score(id) > score_at_rank(REVIEW_THRESHOLD - 1)
end
end
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