discourse/lib/suggested_topics_builder.rb

require_dependency 'topic_list'

class SuggestedTopicsBuilder

  attr_reader :excluded_topic_ids
  attr_reader :results

  def initialize(topic)
    @excluded_topic_ids = [topic.id]
    @results = []
  end

  def add_results(results)

    # WARNING .blank? will execute an Active Record query
    return unless results

    # Only add results if we don't have those topic ids already
    results = results.where('topics.id NOT IN (?)', @excluded_topic_ids)
                     .where(closed: false, archived: false, visible: true)
                     .to_a

    unless results.empty?
      # Keep track of the ids we've added
      @excluded_topic_ids.concat results.map {|r| r.id}
      @results.concat results
    end
  end

  def results_left
    SiteSetting.suggested_topics - @results.size
  end

  def full?
    results_left == 0
  end

  def size
    @results.size
  end

end