discourse/lib/topics_filter.rb

# frozen_string_literal: true

class TopicsFilter
  def initialize(guardian:, scope: Topic, category_id: nil)
    @guardian = guardian
    @scope = scope
    @category = category_id.present? ? Category.find_by(id: category_id) : nil
  end

  def filter_tags(tag_names:, match_all: true, exclude: false)
    return @scope if !SiteSetting.tagging_enabled?
    return @scope if tag_names.blank?

    tag_ids =
      DiscourseTagging
        .filter_visible(Tag, @guardian)
        .where_name(tag_names)
        .pluck(:id, :target_tag_id)

    tag_ids.flatten!
    tag_ids.uniq!
    tag_ids.compact!

    return @scope.none if match_all && tag_ids.length != tag_names.length
    return @scope if tag_ids.empty?

    self.send(
      "#{exclude ? "exclude" : "include"}_topics_with_#{match_all ? "all" : "any"}_tags",
      tag_ids,
    )

    @scope
  end

  def filter_status(status:)
    case status
    when "open"
      @scope = @scope.where("NOT topics.closed AND NOT topics.archived")
    when "closed"
      @scope = @scope.where("topics.closed")
    when "archived"
      @scope = @scope.where("topics.archived")
    when "listed"
      @scope = @scope.where("topics.visible")
    when "unlisted"
      @scope = @scope.where("NOT topics.visible")
    when "deleted"
      if @guardian.can_see_deleted_topics?(@category)
        @scope = @scope.unscope(where: :deleted_at).where("topics.deleted_at IS NOT NULL")
      end
    end

    @scope
  end

  private

  def exclude_topics_with_all_tags(tag_ids)
    where_clause = []

    tag_ids.each_with_index do |tag_id, index|
      sql_alias = "tt#{index}"

      @scope =
        @scope.joins(
          "LEFT JOIN topic_tags #{sql_alias} ON #{sql_alias}.topic_id = topics.id AND #{sql_alias}.tag_id = #{tag_id}",
        )

      where_clause << "#{sql_alias}.topic_id IS NULL"
    end

    @scope = @scope.where(where_clause.join(" OR "))
  end

  def exclude_topics_with_any_tags(tag_ids)
    @scope =
      @scope.where(
        "topics.id NOT IN (SELECT DISTINCT topic_id FROM topic_tags WHERE topic_tags.tag_id IN (?))",
        tag_ids,
      )
  end

  def include_topics_with_all_tags(tag_ids)
    tag_ids.each_with_index do |tag_id, index|
      @scope =
        @scope.joins(
          "INNER JOIN topic_tags tt#{index} ON tt#{index}.topic_id = topics.id AND tt#{index}.tag_id = #{tag_id}",
        )
    end
  end

  def include_topics_with_any_tags(tag_ids)
    @scope = @scope.joins(:topic_tags).where("topic_tags.tag_id IN (?)", tag_ids).distinct(:id)
  end
end