module Securable
  def self.included(base)
    base.extend(ClassMethods)
  end
  class Secured
    def initialize(p, o)
      @o = o
      @o.class.methods_with_permissions(p) {|m| define_proxy_method(m)}
    end

    def self.is_permission_match?(p, min_p)
      case min_p
        when :guest
          true
        when :admin
          (p == :admin)
        when :owner
          (p == :admin || p == :owner)
        else
          false
      end
    end

    private

    def define_proxy_method(m)
      (class << self; self; end).class_eval do
        define_method m do |*args|
          @o.send m, *args
        end
      end
    end
  end
  module ClassMethods
    def methods_with_permissions(p)
      (@method_permissions ||= {}).each do |k, v|
        yield k if Securable::Secured.is_permission_match?(p, v)
      end
      nil
    end
    private
    def attr_accessor_secure(p, *args)
      args.each do |a|
        require_permissions_for_method(a, p)
        attr_reader a
      end
    end

    def require_permissions_for_method(m, p)
      (@method_permissions ||= {})[m] = p
    end
  end
end

class User
  include Securable
  attr_accessor_secure :guest, :username
  attr_accessor_secure :owner, :email, :password
  attr_accessor_secure :admin, :role
end

u = User.new
u.username = 'kurt'
u.password = 'test'
u.email = 'kurt@mubble.net'

s = User::Secured.new(:guest, u)