module Neo4j::ActiveRel
  module Persistence
    extend ActiveSupport::Concern
    include Neo4j::Shared::Persistence

    class RelInvalidError < RuntimeError; end

    class ModelClassInvalidError < RuntimeError; end

    def clear_association_cache; end

    def save(*)
      update_magic_properties
      create_or_update
    end

    def save!(*args)
      raise RelInvalidError.new(self) unless save(*args)
    end

    def create_model(*)
      confirm_node_classes
      create_magic_properties
      set_timestamps
      properties = convert_properties_to :db, props
      rel = _create_rel(from_node, to_node, properties)
      init_on_load(rel._persisted_obj, from_node, to_node, @rel_type)
      true
    end

    module ClassMethods

      # Creates a new relationship between objects
      # @param [Hash] props the properties the new relationship should have
      def create(props = {})
        relationship_props = extract_association_attributes!(props) || {}
        new(props).tap do |obj|
          relationship_props.each do |prop, value|
            obj.send("#{prop}=", value)
          end
          obj.save
        end
      end

      # Same as #create, but raises an error if there is a problem during save.
      def create!(*args)
        raise RelInvalidError.new(self) unless create(*args)
      end
    end

    private

    def confirm_node_classes
      [from_node, to_node].each do |node|
        type = from_node == node ? :_from_class : :_to_class
        next if allows_any_class?(type)
        raise ModelClassInvalidError, "Node class was #{node.class}, expected #{self.class.send(type)}" unless class_as_constant(type) == node.class
      end
    end

    def _create_rel(from_node, to_node, *args)
      props = self.class.default_property_values(self)
      props.merge!(args[0]) if args[0].is_a?(Hash)
      set_classname(props)
      _rel_creation_query(from_node, to_node, props)
    end

    def class_as_constant(type)
      given_class = self.class.send(type)
      case given_class
      when String
        given_class.constantize
      when Symbol
        given_class.to_s.constantize
      else
        given_class
      end
    end

    def allows_any_class?(type)
      self.class.send(type) == :any || self.class.send(type) == false
    end

    private

    def _rel_creation_query(from_node, to_node, props)
      from_class = from_node.class
      to_class = to_node.class
      Neo4j::Session.query.match(n1: from_class.mapped_label_name, n2: to_class.mapped_label_name)
        .where("n1.#{from_class.primary_key} = {from_node_id}")
        .where("n2.#{to_class.primary_key} = {to_node_id}")
        .params(from_node_id: from_node.id, to_node_id: to_node.id)
        .create("(n1)-[r:`#{type}`]->(n2)")
        .with('r').set(r: props).return(:r).first.r
    end

  end
end