pallastrade-promotions

name

pallastrade-promotions

description

Use when the user is working with PallasTrade promotions, discounts, or coupon codes — configuring a promo, writing a custom promotion rule, building a custom action, applying a discount programmatically. Common phrasings include "create promotion", "coupon code", "discount", "BOGO", "free shipping promotion", "promotion not applying", "custom promotion rule", "stack promotions". Provides the Promotion / PromotionRule / PromotionAction / Calculator graph and the customization points documented at `docs/developer/how-to/custom-promotion.mdx`.

PallasTrade Promotions

A promotion is "if X is true about the cart, do Y." PallasTrade breaks that into:

Promotion           — the campaign (name, dates, code, usage limits)
  ├── PromotionRule × n        — eligibility checks: "if X is true"
  ├── PromotionAction × n      — what to do: "create a discount", "free shipping"
  │     └── Calculator         — how much (flat $, %, per-item, etc.)
  └── PromotionCategory        — admin grouping

A promo can have multiple rules (ANDed or ORed via match_policy) and multiple actions (all fire when eligible).

Promotion attributes

PallasTrade::Promotion.create!(
  name: 'Summer Sale 2026',
  code: 'SUMMER20',                 # required for the default kind: :coupon_code; pass kind: :automatic for no-code promos
  starts_at: Date.new(2026, 6, 1),
  expires_at: Date.new(2026, 9, 1),
  usage_limit: 1000,                # max total redemptions; nil = unlimited
  match_policy: 'all',              # 'all' (AND) or 'any' (OR) for rule matching
  advertise: true                   # show in store header / banners
)

• Coupon codes vs automatic: promotions have a kind enum — coupon_code (default) or automatic. Coupon-code promos require code (normalized to lowercase; matched case-insensitively). For promos that apply automatically when rules match, pass kind: :automatic — leaving code nil without it fails validation, since kind defaults to coupon_code.
• Bulk codes: for many unique single-use codes (one per email blast, influencer, etc.), set multi_codes: true + number_of_codes: (optionally code_prefix:) — PallasTrade generates PallasTrade::CouponCode records (promotion.coupon_codes) instead of using the single code column, and usage_limit doesn't apply.
• Console caveat: store is validated as present and auto-filled from PallasTrade::Current.store — in a bare console/rake context set it explicitly (store: PallasTrade::Store.default) or the create! above raises.
• Per-customer limits: add a PallasTrade::Promotion::Rules::OneUsePerUser rule. The customer must be logged in (anonymous orders can't enforce per-customer limits — no identity).

Built-in PromotionRule subclasses

Each rule subclasses PallasTrade::PromotionRule and implements eligible?(promotable, options = {}).

Rule	Eligibility
Channel	The order's channel is in a configured set of channels
Country	The order's shipping country is in the configured ISO code list (defaults to the store's default country)
Currency	The cart's currency matches
CustomerGroup	The customer is in a specific group
FirstOrder	The customer hasn't completed an order before
ItemTotal	Order subtotal meets a threshold (configurable operator)
Market	The order's market matches
OneUsePerUser	The customer hasn't used this promo before
OptionValue	At least one variant in the cart has a matching option value
Product	At least one matching product is in the cart
Taxon	At least one matching category is in the cart
User	The specific customer is on the order
UserLoggedIn	The customer is authenticated

Rules combine via the promo's match_policy:

• all — every rule must be eligible (default)
• any — at least one rule must be eligible

Built-in PromotionAction subclasses

Each action subclasses PallasTrade::PromotionAction and implements perform(options = {}).

Action	Effect
CreateAdjustment	One adjustment on the whole order (e.g. $10 off the total)
CreateItemAdjustments	One adjustment per eligible line item (e.g. 20% off matching products)
CreateLineItems	Auto-add configured variants to the cart when eligible (added at normal price — pair with a discount action to make them free / BOGO)
FreeShipping	Zero out shipping cost

Discount actions consult a Calculator for the amount. PallasTrade::Calculator::FlatRate gives a flat amount off; PallasTrade::Calculator::PercentOnLineItem gives a percentage off matching items; PallasTrade::Calculator::FlatPercentItemTotal gives a percentage off the cart total. The full calculator catalog lives at PallasTrade::Calculator subclasses in pallastrade_core/app/models/pallastrade/calculator/.

Custom PromotionRule

Subclass PallasTrade::PromotionRule, implement applicable? + eligible?, register in an initializer, add an admin partial:

# app/models/pallastrade/promotion/rules/minimum_quantity.rb
module PallasTrade
  class Promotion
    module Rules
      class MinimumQuantity < PallasTrade::PromotionRule
        preference :quantity, :integer, default: 5

        def applicable?(promotable)
          promotable.is_a?(PallasTrade::Order)
        end

        def eligible?(order, options = {})
          total_quantity = order.line_items.sum(&:quantity)
          return true if total_quantity >= preferred_quantity

          eligibility_errors.add(:base, "Order must contain at least #{preferred_quantity} items")
          false
        end
      end
    end
  end
end

# config/initializers/pallastrade.rb
Rails.application.config.after_initialize do
  PallasTrade.promotions.rules << PallasTrade::Promotion::Rules::MinimumQuantity
end

# app/views/pallastrade/admin/promotion_rules/forms/_minimum_quantity.html.erb
# The partial name must match the rule's `key` (`api_type` — demodulized, underscored class name by default).
# Action partials go in app/views/pallastrade/admin/promotion_actions/forms/.
<div class="row mb-3">
  <%= f.pallastrade_number_field :preferred_quantity, label: PallasTrade.t(:minimum_quantity) %>
</div>

Add locale entries under pallastrade.minimum_quantity and pallastrade.promotion_rule_types.minimum_quantity.{name,description}. The admin selector reads from those keys.

Key methods on a rule

Method	Required	Description
applicable?(promotable)	Yes	Whether this rule can evaluate the promotable (usually promotable.is_a?(PallasTrade::Order))
eligible?(promotable, options = {})	Yes	Whether the promotable meets the rule. Add messages to eligibility_errors to explain false
actionable?(line_item)	No	Whether a specific line item should receive the action's adjustment. Default true. Override for rules that target specific items (product, category)

eligible? is called per-order during the cart pipeline. Keep it cheap — N+1 queries here are a common cart-pipeline performance issue.

Custom PromotionAction

Subclass PallasTrade::PromotionAction and implement perform. Discount actions also include PallasTrade::CalculatedAdjustments + PallasTrade::AdjustmentSource:

# app/models/pallastrade/promotion/actions/tiered_discount.rb
module PallasTrade
  class Promotion
    module Actions
      class TieredDiscount < PallasTrade::PromotionAction
        include PallasTrade::CalculatedAdjustments
        include PallasTrade::AdjustmentSource

        before_validation -> { self.calculator ||= Calculator::FlatRate.new }

        def perform(options = {})
          order = options[:order]
          return false unless order.present?

          create_unique_adjustment(order, order)
        end

        def compute_amount(order)
          discount = case order.item_total
                     when 100..Float::INFINITY then 25
                     when 50..99.99 then 10
                     else 0
                     end

          # Discounts are negative; cap to prevent negative orders
          [discount, order.item_total].min * -1
        end
      
    
  

# config/initializers/pallastrade.rb
Rails.application.config.after_initialize do
  PallasTrade.promotions.actions << PallasTrade::Promotion::Actions::TieredDiscount
end

Non-discount actions (award points, send notifications) don't need the calculator includes — just implement perform.

Key methods on an action

Method	Required	Description
perform(options = {})	Yes	Called when the promotion activates. options includes :order and :promotion. Return true if the action was applied
compute_amount(adjustable)	For discount actions	Return the adjustment amount (negative for discounts). Cap at the adjustable's total
revert(options = {})	No	Called when the promotion deactivates. Use to undo side effects (e.g., remove added line items)

perform runs during cart recalculate. Keep it cheap and idempotent — recalculate fires on many cart changes.

Helper methods from the includes

# PallasTrade::AdjustmentSource:
create_unique_adjustment(order, adjustable)
create_unique_adjustments(order, order.line_items)
create_unique_adjustments(order, order.line_items) do |line_item|
  promotion.line_item_actionable?(order, line_item)
end

# PallasTrade::CalculatedAdjustments:
compute(adjustable)                                # calls calculator.compute(adjustable)
self.calculator_type = 'PallasTrade::Calculator::FlatRate'
self.class.calculators                              # available calculators

Custom Calculator

Calculators answer "given X, how much?" — the same calculator subclass can be used by multiple action types.

module PallasTrade
  class Calculator::PercentWithCap < PallasTrade::Calculator
    preference :percent, :decimal, default: 10
    preference :cap_amount, :decimal, default: 50

    def compute(object)
      base = object.amount.to_d
      raw = base * (preferred_percent / 100.0)
      [raw, preferred_cap_amount].min
    end
  end
end

Register so the action's "available calculators" picker shows it:

Rails.application.config.after_initialize do
  PallasTrade.calculators.promotion_actions_create_item_adjustments << PallasTrade::Calculator::PercentWithCap
  # order-level actions read from PallasTrade.calculators.promotion_actions_create_adjustments
end

Promotion stacking

Multiple promotions can each create adjustments, but PallasTrade does not stack them on the same target. During recalculation PallasTrade::Adjustable::Adjuster::Promotion (registered by default in Rails.application.config.pallastrade.adjusters) keeps only the single best (largest-discount) eligible promo adjustment per adjustable — order, line item, or shipment — and marks competing promo adjustments eligible: false; on a tie the most recently created wins. Promotions targeting different adjustables can still combine (e.g. an order-level discount plus a line-item discount on the same order).

To change this behavior (e.g. allow stacking on one adjustable), swap in a custom adjuster via Rails.application.config.pallastrade.adjusters.

Common promotion problems

"Promotion isn't applying"

Walk this list:

1. Is the code right? Coupon codes are matched case-insensitively but must otherwise match exactly. On multi_codes promos, check the PallasTrade::CouponCode records (promotion.coupon_codes) — each is single-use (state: 'used' once redeemed).
2. Within the window? promotion.starts_at < Time.current && (promotion.expires_at.nil? || promotion.expires_at > Time.current).
3. Usage limit not exceeded? promotion.usage_limit_exceeded?(order) should be false (nil limit = unlimited). To inspect manually, promotion.credits_count is the number of distinct orders that have used the promo — compare it against promotion.usage_limit when a limit is set.
4. Every rule eligible? With match_policy: 'all', every rule must return true. Walk promotion.rules.map { |r| [r.class.name, r.eligible?(order)] } to see which fails. Check r.eligibility_errors.full_messages for the reason.
5. Action ran during recalculate? Check order.all_adjustments.promotion — order.adjustments only holds order-level adjustments; CreateItemAdjustments writes to line items and FreeShipping to shipments. If empty, the action never fired — recalculate to retry.

"Custom rule isn't showing in admin UI"

Confirm registration ran: PallasTrade.promotions.rules.include?(PallasTrade::Promotion::Rules::MyRule) should be true after Rails boot. Confirm the admin partial exists at app/views/pallastrade/admin/promotion_rules/forms/_<key>.html.erb (the rule's key / api_type). Confirm locale keys under pallastrade.promotion_rule_types.<underscored_class>.{name,description} are present.

Where to read further

• Core concepts: node_modules/@pallastrade/docs/dist/developer/core-concepts/promotions.md
• Custom rules + actions tutorial: node_modules/@pallastrade/docs/dist/developer/how-to/custom-promotion.md
• Source: PallasTrade::Promotion, PallasTrade::PromotionRule, PallasTrade::PromotionAction, PallasTrade::Calculator in the installed pallastrade_core gem
• Adjustments: see the pallastrade-data-model skill — promotions create Adjustments tied to Orders, LineItems, or Shipments