discourse/lib/topics_filter.rb

# frozen_string_literal: true

class TopicsFilter
  def initialize(guardian:, scope: Topic)
    @guardian = guardian
    @scope = scope
    @notification_levels = Set.new
    @registered_scopes = {}
  end

  def topic_notification_levels
    @registered_scopes.dig(:topic_notification_levels, :params, :notification_levels) || []
  end

  def filter_from_query_string(query_string)
    return @scope if query_string.blank?

    query_string.scan(
      /(?<key_prefix>[-=])?(?<key>[\w-]+):(?<value>[^\s]+)/,
    ) do |key_prefix, key, value|
      case key
      when "created-by"
        filter_created_by_user(usernames: value.split(","))
      when "in"
        @scope = filter_state(state: value)
      when "status"
        @scope = filter_status(status: value)
      when "tags"
        value.scan(
          /^(?<tag_names>([a-zA-Z0-9\-]+)(?<delimiter>[,+])?([a-zA-Z0-9\-]+)?(\k<delimiter>[a-zA-Z0-9\-]+)*)$/,
        ) do |tag_names, delimiter|
          break if key_prefix && key_prefix != "-"

          match_all =
            if delimiter == ","
              false
            else
              true
            end

          @scope =
            filter_tags(
              tag_names: tag_names.split(delimiter),
              exclude: key_prefix.presence,
              match_all: match_all,
            )
        end
      when "category", "categories"
        value.scan(
          /^(?<category_slugs>([a-zA-Z0-9\-:]+)(?<delimiter>[,])?([a-zA-Z0-9\-:]+)?(\k<delimiter>[a-zA-Z0-9\-:]+)*)$/,
        ) do |category_slugs, delimiter|
          break if key_prefix && key_prefix != "="

          @scope =
            filter_categories(
              category_slugs: category_slugs.split(delimiter),
              exclude_subcategories: key_prefix.presence,
            )
        end
      end
    end

    @registered_scopes.each_value { |value| @scope = value[:block].call(*value[:params].values) }

    @scope
  end

  def filter_status(status:, category_id: nil)
    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"
      category = category_id.present? ? Category.find_by(id: category_id) : nil

      if @guardian.can_see_deleted_topics?(category)
        @scope = @scope.unscope(where: :deleted_at).where("topics.deleted_at IS NOT NULL")
      end
    when "public"
      @scope = @scope.joins(:category).where("NOT categories.read_restricted")
    end

    @scope
  end

  private

  def filter_created_by_user(usernames:)
    register_scope(
      key: :created_by_user,
      params: {
        usernames: usernames.map(&:downcase),
      },
    ) do |usernames_lower|
      @scope.joins(:user).where("users.username_lower IN (?)", usernames_lower)
    end
  end

  def filter_state(state:)
    case state
    when "pinned"
      @scope.where(
        "topics.pinned_at IS NOT NULL AND topics.pinned_until > topics.pinned_at AND ? < topics.pinned_until",
        Time.zone.now,
      )
    when "bookmarked"
      return @scope.none unless @guardian.user

      @scope.joins(:topic_users).where(
        "topic_users.bookmarked AND topic_users.user_id = ?",
        @guardian.user.id,
      )
    else
      return @scope.none if !@guardian.user

      topic_notification_levels = Set.new

      state
        .split(",")
        .each do |topic_notification_level|
          if level = TopicUser.notification_levels[topic_notification_level.to_sym]
            topic_notification_levels << level
          end
        end

      register_scope(
        key: :topic_notification_levels,
        params: {
          notification_levels: topic_notification_levels.to_a,
        },
      ) do |notification_levels|
        @scope.joins(:topic_users).where(
          "topic_users.notification_level IN (:topic_notification_levels) AND topic_users.user_id = :user_id",
          topic_notification_levels: notification_levels,
          user_id: @guardian.user.id,
        )
      end

      @scope
    end
  end

  def filter_categories(category_slugs:, exclude_subcategories: false)
    category_ids = Category.ids_from_slugs(category_slugs)

    category_ids =
      Category
        .where(id: category_ids)
        .filter { |category| @guardian.can_see_category?(category) }
        .map(&:id)

    # Don't return any records if the user does not have access to any of the categories
    return @scope.none if category_ids.length < category_slugs.length

    if !exclude_subcategories
      category_ids = category_ids.flat_map { |category_id| Category.subcategory_ids(category_id) }
    end

    register_scope(key: :categories, params: { category_ids: category_ids }) do |in_category_ids|
      @scope.joins(:category).where(
        "categories.id IN (:category_ids)",
        category_ids: in_category_ids,
      )
    end

    @scope
  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 topic_tags_alias
    @topic_tags_alias ||= 0
    "tt#{@topic_tags_alias += 1}"
  end

  def exclude_topics_with_all_tags(tag_ids)
    where_clause = []

    tag_ids.each do |tag_id|
      sql_alias = "tt#{topic_tags_alias}"

      @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 do |tag_id|
      sql_alias = "tt#{topic_tags_alias}"

      @scope =
        @scope.joins(
          "INNER JOIN topic_tags #{sql_alias} ON #{sql_alias}.topic_id = topics.id AND #{sql_alias}.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

  def register_scope(key:, params:, &block)
    if registered_scope = @registered_scopes[key]
      registered_scope[:params].each do |param_name, param_value|
        if param_value.is_a?(Array)
          registered_scope[:params][param_name].concat(params[param_name]).tap(&:uniq!)
        else
          registered_scope[:params][param_name] = params[param_name]
        end
      end
    else
      @registered_scopes[key] = { block: block, params: params }
    end
  end
end