Discounts Domain

The discounts domain provides promotions, coupon codes, and discount calculations. It supports percentage and fixed-amount discounts, buy-X-get-Y rules, eligibility conditions, and usage limits.

Install

npx @backcap/cli add discounts

Domain Model

Promotion Entity

A reusable discount campaign with rules, validity period, and stacking configuration.

import { Promotion } from "./domains/discounts/domain/entities/promotion.entity";

const promo = Promotion.create({
  id: crypto.randomUUID(),
  name: "Summer Sale",
  status: "draft",
  rules: [{ type: "percentage", value: 15 }],
  conditions: [{ type: "min_order_amount", value: 5000 }],
  validFrom: new Date("2026-06-01"),
  validUntil: new Date("2026-08-31"),
  maxUses: 1000,
  maxUsesPerCustomer: 1,
  stackable: false,
});

const active = promo.unwrap().activate();

CouponCode Entity

Single-use or limited-use codes tied to a promotion.

import { CouponCode } from "./domains/discounts/domain/entities/coupon-code.entity";

const coupon = CouponCode.create({
  id: crypto.randomUUID(),
  code: "SUMMER15",
  promotionId: "promo-1",
  maxRedemptions: 100,
  currentRedemptions: 0,
});

Value Objects

• PromotionStatus — draft, active, inactive
• ValidityPeriod — start/end date range with active check
• UsageLimit — max uses globally and per customer
• DiscountType — percentage, fixed amount, buy-X-get-Y
• Money — amount with currency for calculations

Use Cases

Use Case	Description
CreatePromotion	Create a discount promotion with rules and conditions
ActivatePromotion	Set promotion status to active
DeactivatePromotion	Set promotion status to inactive
GetPromotion	Retrieve promotion details
ListPromotions	Query promotions with filters
CreateCoupon	Generate a coupon code for a promotion
ValidateCoupon	Check if a coupon code is valid
RedeemCoupon	Apply a coupon with usage tracking
ApplyDiscount	Calculate discount for an order context

Ports

• IPromotionRepository — findById, findAll, save
• ICouponRepository — findByCode, findById, save

Contract & Factory

import { createDiscountsService } from "./domains/discounts/contracts";

const discounts = createDiscountsService({
  promotionRepository: myPromotionRepo,
  couponRepository: myCouponRepo,
});

const result = await discounts.applyDiscount({
  couponCode: "SUMMER15",
  orderAmount: 8999,
  orderCurrency: "USD",
  customerId: "cust-1",
});

Domain Events

Event	Payload
PromotionCreated	promotionId, name
PromotionActivated	promotionId
PromotionDeactivated	promotionId
CouponCreated	couponId, code, promotionId
CouponRedeemed	couponId, code, customerId