discourse/app/models/user_archived_message.rb

class UserArchivedMessage < ActiveRecord::Base
  belongs_to :user
  belongs_to :topic

  def self.move_to_inbox!(user_id, topic_id)
    return if (TopicUser.where(
      user_id: user_id,
      topic_id: topic_id,
      notification_level: TopicUser.notification_levels[:muted]
    ).exists?)

    UserArchivedMessage.where(user_id: user_id, topic_id: topic_id).destroy_all
    MessageBus.publish("/topic/#{topic_id}", {type: "move_to_inbox"}, user_ids: [user_id])
  end

  def self.archive!(user_id, topic_id)
    UserArchivedMessage.where(user_id: user_id, topic_id: topic_id).destroy_all
    UserArchivedMessage.create!(user_id: user_id, topic_id: topic_id)
    MessageBus.publish("/topic/#{topic_id}", {type: "archived"}, user_ids: [user_id])
  end
end

# == Schema Information
#
# Table name: user_archived_messages
#
#  id         :integer          not null, primary key
#  user_id    :integer          not null
#  topic_id   :integer          not null
#  created_at :datetime
#  updated_at :datetime
#
# Indexes
#
#  index_user_archived_messages_on_user_id_and_topic_id  (user_id,topic_id) UNIQUE
#