has_policy initialization

has_policy.rb

module HasPolicy
  extend ActiveSupport::Concerns
  
  included do
    delegate :default_policy, to: :'self.class', allow_nil: true, prefix: false
  end
  
  module ClassMethods
    def has_policy(policy_name = nil)
      @@policy_class =
          if policy_name.is_a?(Class)
            policy_name
          elsif policy_name.is_a?(Symbol) || policy_name.is_a?(String)
            policy_name.constantize
          else
            default_policy
          end

      include HasPolicy::PolicyMethods
    end
  
    def default_policy
      if @@default_policy
        @@default_policy
      else
        @@default_policy = "#{self.class.name}Policy".constantize
      end
    end
  end

policy_methods.rb

module HasPolicy::Methods
  extend ActiveSupport::Concerns
  
  include do
    
  end
  
  def policy(policy_name = nil)
    if policy_name
      if policy_name.is_a? Class
        policy_name
      elsif policy_name.is_a?(Simbol) || policy_name.is_a?(String)
        name = policy_name.to_s.camelize
        
        if name[/Policy$/]
          name
        else
          "#{name}Policy"
        end.constantize
      else
        default_policy
      end
    else
      @@policy_class || default_policy
    end.new(current_user, self) # for pundit gem
  end
  
private
  
  def current_user
    User.respond_to?(:current) && User.current # It work for Redmine only
  end
end