Class: SolidusPromotions::Calculators::PercentWithCap

Inherits:
Spree::Calculator
  • Object
show all
Includes:
PromotionCalculator
Defined in:
app/models/solidus_promotions/calculators/percent_with_cap.rb

Overview

A calculator that applies a percentage-based discount with a maximum cap.

This calculator computes a discount as a percentage of the line item’s discountable amount, but limits the total discount to a maximum amount distributed across all applicable line items. The actual discount applied is the lesser of the percentage discount and the proportional share of the maximum cap.

Examples:

calculator = PercentWithCap.new(preferred_percent: 20, preferred_max_amount: 50)
# Line item with $100 discountable amount
# Percentage would be $20 (20% of $100)
# But if the max cap distributes only $15 to this item, it gets $15

Instance Method Summary collapse

Methods included from PromotionCalculator

#description

Instance Method Details

#compute_line_item(line_item) ⇒ BigDecimal

Computes the discount for a line item, capped at a maximum amount.

Calculates both a percentage-based discount and a distributed maximum discount, then returns whichever is smaller. This ensures the discount never exceeds the line item’s proportional share of the maximum cap, even if the percentage would result in a larger discount.

Examples:

Computing discount when percentage is lower than cap

calculator = PercentWithCap.new(preferred_percent: 10, preferred_max_amount: 100)
line_item.discountable_amount # => 50.00
# Percent discount: $5 (10% of $50)
# Max distributed: $25 (assuming equal distribution)
calculator.compute_line_item(line_item) # => 5.00

Computing discount when cap is lower than percentage

calculator = PercentWithCap.new(preferred_percent: 50, preferred_max_amount: 10)
line_item.discountable_amount # => 100.00
# Percent discount: $50 (50% of $100)
# Max distributed: $10 (assuming single line item)
calculator.compute_line_item(line_item) # => 10.00

Parameters:

  • line_item (Spree::LineItem) —

    The line item to calculate the discount for

Returns:

  • (BigDecimal) —

    The discount amount, limited by both the percentage and the max cap

See Also:



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# File 'app/models/solidus_promotions/calculators/percent_with_cap.rb', line 49

def compute_line_item(line_item)
  percent_discount = round_to_currency(line_item.discountable_amount * preferred_percent / 100, line_item.order.currency)
  max_discount = DistributedAmount.new(
    calculable:,
    preferred_amount: preferred_max_amount
  ).compute_line_item(line_item)

  [percent_discount, max_discount].min
end