Class: ActiveShipping::ShipmentPacker

Inherits:
Object
  • Object
show all
Defined in:
lib/active_shipping/shipment_packer.rb

Defined Under Namespace

Classes: ExcessPackageQuantity, OverweightItem

Constant Summary collapse

EXCESS_PACKAGE_QUANTITY_THRESHOLD = 
10_000

Class Method Summary collapse

Class Method Details

.pack(items, dimensions, maximum_weight, currency) ⇒ Object

items - array of hashes containing quantity, grams and price. ex. [{:quantity => 2, :price => 1.0, :grams => 50}] dimensions - [5.0, 15.0, 30.0] maximum_weight - maximum weight in grams currency - ISO currency code



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# File 'lib/active_shipping/shipment_packer.rb', line 14

def self.pack(items, dimensions, maximum_weight, currency)
  return [] if items.empty?
  packages = []

  # Naive in that it assumes weight is equally distributed across all items
  # Should raise early enough in most cases
  total_weight = 0
  items.map!(&:symbolize_keys).each do |item|
    total_weight += item[:quantity].to_i * item[:grams].to_i

    if item[:grams].to_i > maximum_weight
      raise OverweightItem, "The item with weight of #{item[:grams]}g is heavier than the allowable package weight of #{maximum_weight}g"
    end

    if total_weight > maximum_weight * EXCESS_PACKAGE_QUANTITY_THRESHOLD
      raise ExcessPackageQuantity, "Unable to pack more than #{EXCESS_PACKAGE_QUANTITY_THRESHOLD} packages"
    end
  end

  items = items.map(&:dup).sort_by! { |i| i[:grams].to_i }

  state = :package_empty
  while state != :packing_finished
    case state
    when :package_empty
      package_weight, package_value = 0, 0
      state = :filling_package
    when :filling_package
      items.each do |item|
        quantity = if item[:grams].to_i <= 0
          item[:quantity].to_i
        else
          # Grab the max amount of this item we can fit into this package
          # Or, if there are fewer than the max for this item, put
          # what is left into this package
          [(maximum_weight - package_weight) / item[:grams].to_i, item[:quantity].to_i].min
        end

        item_weight = quantity * item[:grams].to_i
        item_value = quantity * Package.cents_from(item[:price])

        package_weight += item_weight
        package_value += item_value

        item[:quantity] = item[:quantity].to_i - quantity
      end

      items.reject! { |i| i[:quantity].to_i == 0 }

      state = :package_full
    when :package_full
      packages << ActiveShipping::Package.new(package_weight, dimensions, :value => package_value, :currency => currency)
      state = items.any? ? :package_empty : :packing_finished
    end
  end

  packages
end