item_gateway.rb

module Navision
  class ItemGateway
    def initialize(options = {})
      @client = options.fetch(:client) { Navision.item_client } # item_client => Savon.client(...)
    end

    def get_product_by_number(number)
      get_result client.call :read, message: { 'No' => number }
    end

    private

    attr_reader :client

    def get_result(response)
      body = response.body || {}
      result = body.fetch(:read_result) { {} }

      result.fetch(:website_items) { {} }
    end

  end
end

item_variant_mapper.rb

module Navision
  class ItemVariantMapper

    def initialize(variant, options = {})
      @variant = variant
      @gateway = options.fetch(:gateway) { Navision.item_gateway }
    end

    def to_variant
      Variant.new(navision_key, msrp, dimensions, weight) # Variant is a Struct
    end

    private

    attr_reader :variant, :gateway
    delegate :mpn, to: :variant

    def gateway_attributes
      @_gateway_attributes ||= gateway.get_product_by_number mpn
    end

    def navision_key
      gateway_attributes[:key]
    end

    def msrp
      gateway_attributes[:msrp]
    end

    def dimensions
      dims = gateway_attributes.values_at(:item_uom_length, :item_uom_width, :item_uom_height)
      dims.join('x') if dims.all?
    end

    def weight
      gateway_attributes[:item_uom_weight]
    end

  end
end