class E  < ActiveOrient::Model
  ## class methods
  class << self
      def naming_convention name=nil
          name.present? ? name.upcase : ref_name.upcase
      end

=begin
Establish constrains on Edges

After applying this method Edges are uniq!

Creates individual indices for child-classes if applied to the class itself.
=end
			def  uniq_index
				create_property  :in,  type: :link, linked_class: :V
				create_property  :out, type: :link, linked_class: :V
				create_index "#{ref_name}_idx", on: [ :in, :out ]
			end

=begin
 Instantiate a new Edge between two Vertices 

 Properties can be placed using the :set-directive or simply by adding key: value- parameter-pairs

 if the creation of an edged is not possible, due to constrains (uniq_index), the already
 connecting edge is returned 

 the method is thread safe, if transaction and update_cache are set to false
=end
			def create from:, to: , set: {}, transaction:  false, update_cache: false, **attributes
				return nil if from.blank? || to.blank?
				set.merge!(attributes) 
				content =  set.empty? ? "" : "content #{set.to_orient.to_json}" 
				statement = "CREATE EDGE #{ref_name} from #{from.to_or} to #{to.to_or} #{content}"
				transaction = true if [:fire, :complete, :run].include?(transaction)
				ir= db.execute( transaction: transaction, process_error: false ){ statement  }
				if update_cache
					from.reload! # get last version 
					to.is_a?(Array)? to.each( &:reload! )  : to.reload!
				end
				to.is_a?(Array)  ? ir : ir.first   # return the plain edge, if only one is created
			rescue RestClient::InternalServerError => e
				sentence=  JSON.parse( e.response)['errors'].last['content']
				if sentence =~ /found duplicated key/
					ref_rid =  sentence.split.last.expand  # return expanded rid
				else
					raise
				end
			rescue ArgumentError => e
				logger.error{ "wrong parameters  #{keyword_arguments} \n\t\t required: from: , to: , attributes:\n\t\t Edge is NOT created"}
			end

=begin
Fires a "delete edge" command to the database.


The where statement can be empty ( "" or {}"), then all edges are removed 

The rid-cache is resetted


to_do: Implement :all=> true directive
       support from: , to: syntax

  :call-seq:
  delete where: 
=end
			def delete where:  

				db.execute { "delete edge #{ref_name} #{db.compose_where(where)}" }
				reset_rid_store

			end


			def connect dir= "-" , **args #  arguments: direction: :both, 
				                 #             count: 1, 
				#                #             as: nil
				
				direction = case dir
										when "-"
											:both
										when '->'
											:out
										when '<-'
											:in
										when Symbol
											dir
										end
				args[:direction] ||= direction


				OrientSupport::MatchConnection.new self, **args
			end

	end   # class methods

	###  instance methods  ###

=begin
Deletes the actual ActiveOrient::Model-Edge-Object

=end

	def delete
		db.execute{ "delete edge #{ref_name} #{rrid}" }
	end
	def to_human
		displayed_attributes =  attributes.reject{|k,_| [:in, :out].include?(k) }
		"<#{self.class.to_s.demodulize}[#{rrid}] :.: #{ attributes[:out].rid}->#{displayed_attributes.to_human}->#{attributes[:in].rid}>"
	end

end