discourse/app/models/topic_converter.rb

# frozen_string_literal: true

class TopicConverter

  attr_reader :topic

  def initialize(topic, user)
    @topic = topic
    @user = user
  end

  def convert_to_public_topic(category_id = nil)
    Topic.transaction do
      category_id =
        if category_id
          category_id
        elsif SiteSetting.allow_uncategorized_topics
          SiteSetting.uncategorized_category_id
        else
          Category.where(read_restricted: false)
            .where.not(id: SiteSetting.uncategorized_category_id)
            .order('id asc')
            .pluck_first(:id)
        end

      PostRevisor.new(@topic.first_post, @topic).revise!(
        @user,
        category_id: category_id,
        archetype: Archetype.default
      )

      update_user_stats
      update_post_uploads_secure_status
      Jobs.enqueue(:topic_action_converter, topic_id: @topic.id)
      Jobs.enqueue(:delete_inaccessible_notifications, topic_id: @topic.id)
      watch_topic(topic)
    end
    @topic
  end

  def convert_to_private_message
    Topic.transaction do
      @topic.update_category_topic_count_by(-1)

      PostRevisor.new(@topic.first_post, @topic).revise!(
        @user,
        category_id: nil,
        archetype: Archetype.private_message
      )

      add_allowed_users
      update_post_uploads_secure_status

      Jobs.enqueue(:topic_action_converter, topic_id: @topic.id)
      Jobs.enqueue(:delete_inaccessible_notifications, topic_id: @topic.id)

      watch_topic(topic)
    end
    @topic
  end

  private

  def posters
    @posters ||= @topic.posts.distinct.pluck(:user_id).to_a
  end

  def update_user_stats
    # update posts count. NOTE that DirectoryItem.refresh will overwrite this by counting UserAction records.
    # update topics count
    UserStat.where(user_id: posters).update_all('post_count = post_count + 1')
    UserStat.where(user_id: @topic.user_id).update_all('topic_count = topic_count + 1')
  end

  def add_allowed_users
    # update posts count. NOTE that DirectoryItem.refresh will overwrite this by counting UserAction records.
    # update topics count
    UserStat.where(user_id: posters).update_all('post_count = post_count - 1')
    UserStat.where(user_id: @topic.user_id).update_all('topic_count = topic_count - 1')

    existing_allowed_users = @topic.topic_allowed_users.pluck(:user_id)
    users_to_allow = posters << @user.id

    (users_to_allow - existing_allowed_users).uniq.each do |user_id|
      @topic.topic_allowed_users.build(user_id: user_id)
    end

    @topic.save!
  end

  def watch_topic(topic)
    @topic.notifier.watch_topic!(topic.user_id)

    @topic.reload.topic_allowed_users.each do |tau|
      next if tau.user_id < 0 || tau.user_id == topic.user_id
      topic.notifier.watch!(tau.user_id)
    end
  end

  def update_post_uploads_secure_status
    @topic.posts.each do |post|
      next if post.uploads.empty?
      post.update_uploads_secure_status
      post.rebake!
    end
  end
end