discourse/plugins/chat/app/services/chat_message_destroyer.rb

# frozen_string_literal: true

class ChatMessageDestroyer
  def destroy_in_batches(chat_messages_query, batch_size: 200)
    chat_messages_query
      .in_batches(of: batch_size)
      .each do |relation|
        destroyed_ids = relation.destroy_all.pluck(:id)
        reset_last_read(destroyed_ids)
        delete_flags(destroyed_ids)
      end
  end

  private

  def reset_last_read(message_ids)
    UserChatChannelMembership.where(last_read_message_id: message_ids).update_all(
      last_read_message_id: nil,
    )
  end

  def delete_flags(message_ids)
    ReviewableChatMessage.where(target_id: message_ids).destroy_all
  end
end