# module Locomotive
#   module Extensions
#     module Page
#       module Templatized
#
#         extend ActiveSupport::Concern
#
#         included do
#
#           ## fields ##
#           field :templatized,             :type => Boolean, :default => false
#           field :templatized_from_parent, :type => Boolean, :default => false
#           field :target_klass_name
#
#           ## validations ##
#           validates_presence_of :target_klass_name, :if => :templatized?
#           validate              :ensure_target_klass_name_security
#
#           ## callbacks ##
#           before_validation :get_templatized_from_parent
#           before_validation :set_slug_if_templatized
#           before_validation :ensure_target_klass_name_security
#           after_save        :propagate_templatized
#
#           ## scopes ##
#           scope :templatized, :where => { :templatized => true }
#
#           ## virtual attributes ##
#           attr_accessor :content_entry
#         end
#
#         # Returns the class specified by the target_klass_name property
#         #
#         # @example
#         #
#         #   page.target_klass_name = 'Locomotive::Entry12345'
#         #   page.target_klass = Locomotive::Entry12345
#         #
#         # @return [ Class ] The target class
#         #
#         def target_klass
#           target_klass_name.constantize
#         end
#
#         # Gives the name which can be used in a liquid template in order
#         # to reference an entry. It uses the slug property if the target klass
#         # is a Locomotive content type or the class name itself for the other classes.
#         #
#         # @example
#         #
#         #   page.target_klass_name = 'Locomotive::Entry12345' # related to the content type Articles
#         #   page.target_entry_name = 'article'
#         #
#         #   page.target_klass_name = 'OurProduct'
#         #   page.target_entry_name = 'our_product'
#         #
#         # @return [ String ] The name in lowercase and underscored
#         #
#         def target_entry_name
#           if self.target_klass_name =~ /^Locomotive::Entry([a-z0-9]+)$/
#             @content_type ||= self.site.content_types.find($1)
#             @content_type.slug.singularize
#           else
#             self.target_klass_name.underscore
#           end
#         end
#
#         # Finds the entry both specified by the target klass and identified by the permalink
#         #
#         # @param [ String ] permalink The permalink of the entry
#         #
#         # @return [ Object ] The document
#         #
#         def fetch_target_entry(permalink)
#           target_klass.find_by_permalink(permalink)
#         end
#
#         protected
#
#         def get_templatized_from_parent
#           return if self.parent.nil?
#
#           if self.parent.templatized?
#             self.templatized        = self.templatized_from_parent = true
#             self.target_klass_name  = self.parent.target_klass_name
#           elsif !self.templatized?
#             self.templatized        = self.templatized_from_parent = false
#             self.target_klass_name  = nil
#           end
#         end
#
#         def set_slug_if_templatized
#           self.slug = 'content_type_template' if self.templatized? && !self.templatized_from_parent?
#         end
#
#         # Makes sure the target_klass is owned by the site OR
#         # if it belongs to the models allowed by the application
#         # thanks to the models_for_templatization option.
#         #
#         def ensure_target_klass_name_security
#           return if !self.templatized? || self.target_klass_name.blank?
#
#           if self.target_klass_name =~ /^Locomotive::Entry([a-z0-9]+)$/
#             content_type = Locomotive::ContentType.find($1)
#
#             if content_type.site_id != self.site_id
#               self.errors.add :target_klass_name, :security
#             end
#           elsif !Locomotive.config.models_for_templatization.include?(self.target_klass_name)
#             self.errors.add :target_klass_name, :security
#           end
#         end
#
#         # Sets the templatized, templatized_from_parent properties of
#         # the children of the current page ONLY IF the templatized
#         # attribute got changed.
#         #
#         def propagate_templatized
#           return unless self.templatized_changed?
#
#           selector = { 'parent_ids' => { '$in' => [self._id] } }
#           operations  = {
#             '$set' => {
#               'templatized'             => self.templatized,
#               'templatized_from_parent' => self.templatized,
#               'target_klass_name'       => self.target_klass_name
#             }
#           }
#
#           self.collection.update selector, operations, :multi => true
#         end
#
#       end
#     end
#   end
# end