expired.rb

class SitesController < ApplicationController
  
  ...
    
  private

    def find_site
      @slug = params[:id].downcase
      @site = Site.find_by(name: @slug)
      if @site.present?
        expired?
      end
    end
    
    def expired?
      last_post = @site.posts.last
      if last_post.present?
        activity_limit = 31
        @days_til_expire = activity_limit - (Time.zone.now - last_post.updated_at)/(3600*24)
        if @days_til_expire < 0
          @site.destroy
          redirect_to main_path(@site.name), notice: 'Previous site here was deleted due to inactivity.'
        end
      end
    end
end