Calculate trends in temporary sets to avoid having to manage items that go below the decay threshold while not having any moments where a half-processed set is accessible to end-users
		
			
				
	
	
		
			115 lines
		
	
	
		
			3.4 KiB
		
	
	
	
		
			Ruby
		
	
	
	
	
	
			
		
		
	
	
			115 lines
		
	
	
		
			3.4 KiB
		
	
	
	
		
			Ruby
		
	
	
	
	
	
# frozen_string_literal: true
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class Trends::Links < Trends::Base
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  PREFIX = 'trending_links'
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  self.default_options = {
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    threshold: 5,
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    review_threshold: 3,
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    max_score_cooldown: 2.days.freeze,
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    max_score_halflife: 8.hours.freeze,
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    decay_threshold: 1,
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  }
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  def register(status, at_time = Time.now.utc)
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    original_status = status.proper
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    return unless (original_status.public_visibility? && status.public_visibility?) &&
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                  !(original_status.account.silenced? || status.account.silenced?) &&
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                  !(original_status.spoiler_text? || original_status.sensitive?)
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    original_status.preview_cards.each do |preview_card|
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      add(preview_card, status.account_id, at_time) if preview_card.appropriate_for_trends?
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    end
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  end
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  def add(preview_card, account_id, at_time = Time.now.utc)
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    preview_card.history.add(account_id, at_time)
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    record_used_id(preview_card.id, at_time)
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  end
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  def refresh(at_time = Time.now.utc)
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    preview_cards = PreviewCard.where(id: (recently_used_ids(at_time) + currently_trending_ids(false, -1)).uniq)
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    calculate_scores(preview_cards, at_time)
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  end
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  def request_review
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    preview_cards = PreviewCard.where(id: currently_trending_ids(false, -1))
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    preview_cards.filter_map do |preview_card|
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      next unless would_be_trending?(preview_card.id) && !preview_card.trendable? && preview_card.requires_review_notification?
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      if preview_card.provider.nil?
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        preview_card.provider = PreviewCardProvider.create(domain: preview_card.domain, requested_review_at: Time.now.utc)
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      else
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        preview_card.provider.touch(:requested_review_at)
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      end
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      preview_card
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    end
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  end
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  protected
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  def key_prefix
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    PREFIX
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  end
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  def klass
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    PreviewCard
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  end
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  private
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  def calculate_scores(preview_cards, at_time)
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    global_items = []
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    locale_items = Hash.new { |h, key| h[key] = [] }
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    preview_cards.each do |preview_card|
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      expected  = preview_card.history.get(at_time - 1.day).accounts.to_f
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      expected  = 1.0 if expected.zero?
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      observed  = preview_card.history.get(at_time).accounts.to_f
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      max_time  = preview_card.max_score_at
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      max_score = preview_card.max_score
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      max_score = 0 if max_time.nil? || max_time < (at_time - options[:max_score_cooldown])
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      score = begin
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        if expected > observed || observed < options[:threshold]
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          0
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        else
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          ((observed - expected)**2) / expected
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        end
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      end
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      if score > max_score
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        max_score = score
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        max_time  = at_time
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        # Not interested in triggering any callbacks for this
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        preview_card.update_columns(max_score: max_score, max_score_at: max_time)
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      end
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      decaying_score = max_score * (0.5**((at_time.to_f - max_time.to_f) / options[:max_score_halflife].to_f))
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      next unless decaying_score >= options[:decay_threshold]
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      global_items << { score: decaying_score, item:  preview_card }
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      locale_items[preview_card.language] << { score: decaying_score, item: preview_card } if valid_locale?(preview_card.language)
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    end
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    replace_items('', global_items)
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    Trends.available_locales.each do |locale|
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      replace_items(":#{locale}", locale_items[locale])
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    end
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  end
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  def filter_for_allowed_items(items)
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    items.select { |item| item[:item].trendable? }
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  end
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  def would_be_trending?(id)
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    score(id) > score_at_rank(options[:review_threshold] - 1)
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  end
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end
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