Add YARD docs to SolidusPromotions::Benefit

promotions/app/models/solidus_promotions/benefit.rb

@@ -1,29 +1,90 @@
 # frozen_string_literal: true
 
 module SolidusPromotions
-  # Base class for all types of benefit.
+  # Base class for all promotion benefits.
   #
-  # Benefits perform the necessary tasks when a promotion is activated
-  # by an event and determined to be eligible.
+  # A Benefit is the active part of a promotion: once a promotion becomes
+  # eligible for a given promotable (order, line item, or shipment), the benefit
+  # determines how much discount to apply and produces the corresponding
+  # adjustments.
+  #
+  # Subclasses specialize the discounting target (orders, line items, or
+  # shipments) and usually include one of the following mixins to integrate with
+  # Solidus' adjustment system:
+  # - SolidusPromotions::Benefits::OrderBenefit
+  # - SolidusPromotions::Benefits::LineItemBenefit
+  # - SolidusPromotions::Benefits::ShipmentBenefit
+  #
+  # A benefit can discount any object for which {#can_discount?} returns true.
+  # Implementors must provide a calculator via Spree::CalculatedAdjustments and
+  # may override methods such as {#adjustment_label}.
+  #
+  # Usage example
+  #
+  #   benefit = SolidusPromotions::Benefits::AdjustLineItem.new(promotion: promo)
+  #   if benefit.can_discount?(line_item)
+  #     discount = benefit.discount(line_item)
+  #     # => #<SolidusPromotions::ItemDiscount ...>
+  #   end
+  #
+  # @see SolidusPromotions::Promotion
+  # @see Spree::CalculatedAdjustments
   class Benefit < Spree::Base
     include Spree::Preferences::Persistable
     include Spree::CalculatedAdjustments
     include Spree::AdjustmentSource
+
     before_destroy :remove_adjustments_from_incomplete_orders
     before_destroy :raise_for_adjustments_for_completed_orders
 
+    # @!attribute [rw] promotion
+    #   The owning promotion.
+    #   @return [SolidusPromotions::Promotion]
     belongs_to :promotion, inverse_of: :benefits
+    # @!attribute [rw] original_promotion_action
+    #   Back-reference to the original Solidus (Spree) promotion action, when migrated.
+    #   @return [Spree::PromotionAction, nil]
     belongs_to :original_promotion_action, class_name: "Spree::PromotionAction", optional: true
+    # @!attribute [r] adjustments
+    #   Adjustments created by this benefit.
+    #   @return [ActiveRecord::Associations::CollectionProxy<Spree::Adjustment>]
     has_many :adjustments, class_name: "Spree::Adjustment", as: :source, dependent: :restrict_with_error
+    # @!attribute [r] shipping_rate_discounts
+    #   Shipping-rate-level discounts generated by this benefit.
+    #   @return [ActiveRecord::Associations::CollectionProxy<SolidusPromotions::ShippingRateDiscount>]
     has_many :shipping_rate_discounts, class_name: "SolidusPromotions::ShippingRateDiscount", inverse_of: :benefit, dependent: :restrict_with_error
+    # @!attribute [r] conditions
+    #   Conditions attached to this benefit.
+    #   @return [ActiveRecord::Associations::CollectionProxy<SolidusPromotions::Condition>]
     has_many :conditions, class_name: "SolidusPromotions::Condition", inverse_of: :benefit, dependent: :destroy
 
+    # @!method self.of_type(type)
+    #   Restricts benefits to the given STI type(s).
+    #   @param type [String, Symbol, Class, Array<String,Symbol,Class>] a single type or list of types
+    #   @return [ActiveRecord::Relation<SolidusPromotions::Benefit>]
     scope :of_type, ->(type) { where(type: Array.wrap(type).map(&:to_s)) }
 
+    # Returns relations that should be preloaded for this condition.
+    #
+    # Override this method in subclasses to specify associations that should be eager loaded
+    # to avoid N+1 queries when evaluating conditions.
+    #
+    # @return [Array<Symbol>] An array of association names to preload
     def preload_relations
       [:calculator]
     end
 
+    # Whether this benefit can discount the given object.
+    #
+    # Subclasses must implement this according to the kinds
+    # of objects they are able to discount.
+    #
+    # @param object [Object] a potential adjustable (order, line item, or shipment)
+    # @return [Boolean]
+    # @raise [NotImplementedError] when not implemented by the subclass/mixin
+    # @see SolidusPromotions::Benefits::OrderBenefit,
+    #      SolidusPromotions::Benefits::LineItemBenefit,
+    #      SolidusPromotions::Benefits::ShipmentBenefit
     def can_discount?(object)
       raise NotImplementedError, "Please implement the correct interface, or include one of the `SolidusPromotions::Benefits::OrderBenefit`, " \
         "`SolidusPromotions::Benefits::LineItemBenefit` or `SolidusPromotions::Benefits::ShipmentBenefit` modules"
@@ -57,12 +118,23 @@ def discount(adjustable, ...)
       )
     end
 
-    # Ensure a negative amount which does not exceed the object's amount
+    # Computes the discount amount for the given adjustable.
+    #
+    # Ensures the returned amount is negative and does not exceed the
+    # adjustable's discountable amount.
+    #
+    # @param adjustable [#discountable_amount] the adjustable to compute for
+    # @param ... [args, kwargs] additional arguments forwarded to the calculator
+    # @return [BigDecimal] a negative amount suitable for creating an adjustment
     def compute_amount(adjustable, ...)
       promotion_amount = calculator.compute(adjustable, ...) || Spree::ZERO
       [adjustable.discountable_amount, promotion_amount.abs].min * -1
     end
 
+    # Builds the localized label for adjustments created by this benefit.
+    #
+    # @param adjustable [Object]
+    # @return [String]
     def adjustment_label(adjustable)
       I18n.t(
         "solidus_promotions.adjustment_labels.#{adjustable.class.name.demodulize.underscore}",
@@ -71,6 +143,9 @@ def adjustment_label(adjustable)
       )
     end
 
+    # Partial path used for admin forms for this benefit type.
+    #
+    # @return [String]
     def to_partial_path
       "solidus_promotions/admin/benefit_fields/#{model_name.element}"
     end
@@ -80,14 +155,30 @@ def level
         "`SolidusPromotions::Benefits::LineItemBenefit` or `SolidusPromotions::Benefits::ShipmentBenefit` modules"
     end
 
+    # Returns the set of condition classes that can still be attached to this benefit.
+    # Already-persisted conditions are excluded.
+    #
+    # @return [Set<Class<SolidusPromotions::Condition>>]
     def available_conditions
       possible_conditions - conditions.select(&:persisted?)
     end
 
+    # Returns the calculators allowed for this benefit type.
+    #
+    # @return [Array<Class>] calculator classes
     def available_calculators
       SolidusPromotions.config.promotion_calculators[self.class] || []
     end
 
+    # Verifies if the promotable satisfies all applicable conditions of this benefit.
+    #
+    # When dry_run is true, an {SolidusPromotions::EligibilityResults} entry is
+    # recorded for each condition with success/error details; otherwise, the
+    # evaluation short-circuits on the first failure.
+    #
+    # @param promotable [Object] the entity being evaluated (e.g., Spree::Order, Spree::LineItem)
+    # @param dry_run [Boolean] whether to collect detailed eligibility information
+    # @return [Boolean] true when all applicable conditions are eligible
     def eligible_by_applicable_conditions?(promotable, dry_run: false)
       applicable_conditions = conditions.select do |condition|
         condition.applicable?(promotable)
@@ -116,18 +207,35 @@ def eligible_by_applicable_conditions?(promotable, dry_run: false)
       end.all?
     end
 
+    # All line items of the order that are eligible for this benefit.
+    #
+    # @param order [Spree::Order]
+    # @return [Array<Spree::LineItem>] eligible line items
     def applicable_line_items(order)
       order.discountable_line_items.select do |line_item|
         eligible_by_applicable_conditions?(line_item)
       end
     end
 
+    # Base set of order-level condition classes available to all benefits.
+    #
+    # These generic order conditions apply regardless of the concrete benefit
+    # type, as every benefit ultimately operates within the context of an order.
+    # Concrete benefit subclasses may extend or override this to include
+    # additional applicable conditions that are specific to their discount
+    # target (e.g., line-item or shipment conditions).
+    #
+    # @return [Set<Class<SolidusPromotions::Condition>>]
     def possible_conditions
       Set.new(SolidusPromotions.config.order_conditions)
     end
 
     private
 
+    # Prevents destroying a benefit when it has adjustments on completed orders.
+    #
+    # Adds an error and aborts the destroy callback chain when such adjustments exist.
+    # @api private
     def raise_for_adjustments_for_completed_orders
       if adjustments.joins(:order).merge(Spree::Order.complete).any?
         errors.add(:base, :cannot_destroy_if_order_completed)