package_fitting_checker.rb

module Delivery
  class PackageFittingChecker
    def self.fit?(shipping_method_id, quantities_with_max_units_and_shipping_package_categories)
      case shipping_method_id
      when "correos", "d_post"
        max_units_per_package = :max_units_per_correos_package
      when "ups_envelope"
        max_units_per_package = :max_units_per_ups_package
      when "dhl", "ups_express_saver", "ups_standard"
        return true
      else
        raise "Unknown shipping method!"
      end

      return false unless quantities_with_max_units_and_shipping_package_categories.map{|elem| elem[:shipping_package_category]}.compact.uniq.size == 1

      sum = 0
      quantities_with_max_units_and_shipping_package_categories.each do |elem|
        return false unless elem[max_units_per_package] > 0
        sum += filling_ratio(elem[:quantity], elem[max_units_per_package])
        return false if sum > 100
      end
      true
    end

    private

    def self.filling_ratio(quantity, max_units)
      (quantity / max_units.to_f) * 100
    end
  end
end