You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: database_subscriber.rb
    path of file: ./repos/ahoy_email/lib/ahoy_email
    
    the code of the file until where you have to start completion: module AhoyEmail
  class DatabaseSubscriber
    def track_send(event)
      # use has_history to store on Ahoy::Messages
    end

    def track_click(event)
      Ahoy::Click.create!(campaign: event[:campaign], token: event[:token])
    end

    def stats(campaign)
      sends = Ahoy:
    
    def stats(campaign)
      sends = Ahoy::Message.where(campaign: campaign).count

      if defined?(ActiveRecord) && Ahoy::Click < ActiveRecord::Base
        result = Ahoy::Click.where(campaign: campaign).select("COUNT(*) AS clicks, COUNT(DISTINCT token) AS unique_clicks").to_a[0]
        clicks = result.clicks
        unique_clicks = result.unique_clicks
      else
        clicks = Ahoy::Click.where(campaign: campaign).count
        # TODO use aggregation framework
        unique_clicks = Ahoy::Click.where(campaign: campaign).distinct(:token).count
      end