module CacheableFlash
  module Controller
    def self.included(base)
      base.prepend_around_action :write_flash_to_cookie
    end

    def write_flash_to_cookie
      yield self

      cookie_flash = begin
        JSON.parse(cookies["flash"] || "{}")
      rescue JSON::ParserError
        {}
      end

      flash.each do |key, value|
        if cookie_flash[key.to_s].blank?
          cookie_flash[key.to_s] = value
        else
          cookie_flash[key.to_s] << "<br/>#{value}" # TODO should be an array
        end
      end

      cookies['flash'] = cookie_flash.to_json
      flash.clear
    end
  end
end