Class: SolidusPromotions::Benefits::AdjustLineItemQuantityGroups

Inherits:
AdjustLineItem show all
Defined in:
app/models/solidus_promotions/benefits/adjust_line_item_quantity_groups.rb

Defined Under Namespace

Classes: Item

Instance Method Summary collapse

Methods inherited from AdjustLineItem

#possible_conditions

Methods included from LineItemBenefit

#can_discount?, #level

Methods inherited from SolidusPromotions::Benefit

#adjustment_label, #applicable_line_items, #available_calculators, #available_conditions, #can_discount?, #discount, #eligible_by_applicable_conditions?, #level, #possible_conditions, #preload_relations, #to_partial_path

Instance Method Details

#compute_amount(line_item) ⇒ Object

Computes the amount for the adjustment based on the line item and any other applicable items in the order. The conditions for this specific adjustment are as follows:

Setup

We have a quantity group promotion on t-shirts. If a user orders 3 t-shirts, they get $5 off of each. The shirts come in one size and three colours: red, blue, and white.

Scenario 1

User has 2 red shirts, 1 white shirt, and 1 blue shirt in their order. We want to compute the adjustment amount for the white shirt.

Result: -$5

Reasoning: There are a total of 4 items that are eligible for the promotion. Since that is greater than 3, we can discount the items. The white shirt has a quantity of 1, therefore it will get discounted by adjustment_amount * 1 or $5.

Scenario 1-1

What about the blue shirt? How much does it get discounted?

Result: $0

Reasoning: We have a total quantity of 4. However, we only apply the adjustment to groups of 3. Assuming the white and red shirts have already had their adjustment calculated, that means 3 units have been discounted. Leaving us with a lonely blue shirt that isn’t part of a group of 3. Therefore, it does not receive the discount.

Scenario 2

User has 4 red shirts in their order. What is the amount?

Result: -$15

Reasoning: The total quantity of eligible items is 4, so we the adjustment will be non-zero. However, we only apply it to groups of 3, therefore there is one extra item that is not eligible for the adjustment. adjustment_amount * 3 or $15.



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# File 'app/models/solidus_promotions/benefits/adjust_line_item_quantity_groups.rb', line 54

def compute_amount(line_item)
  adjustment_amount = calculator.compute(Item.new(line_item))
  return BigDecimal("0") if adjustment_amount.nil? || adjustment_amount.zero?

  adjustment_amount = adjustment_amount.abs

  order = line_item.order
  line_items = applicable_line_items(order)

  item_units = line_items.sort_by do |applicable_line_item|
    [-applicable_line_item.quantity, applicable_line_item.id]
  end.flat_map do |applicable_line_item|
    Array.new(applicable_line_item.quantity) do
      Item.new(applicable_line_item)
    end
  end

  item_units_in_groups = item_units.in_groups_of(preferred_group_size, false)
  item_units_in_groups.select! { |group| group.length == preferred_group_size }
  usable_quantity = item_units_in_groups.flatten.count { |item_unit| item_unit.line_item == line_item }

  amount = adjustment_amount * usable_quantity
  [line_item.discountable_amount, amount].min * -1
end