@dhruvp13/promo-code-core

Zero-dependency validation and calculation engine for coupon/promo-code systems. Framework-agnostic — bring your own database via the CouponRepository interface.

Install

bun add @dhruvp13/promo-code-core

Usage

import { validateCoupon, type CouponRepository } from '@dhruvp13/promo-code-core'

declare const repo: CouponRepository<'coin' | 'subscription'>

const result = await validateCoupon(repo, {
  code: 'SAVE20',
  userId: 'user-1',
  purchaseType: 'coin',
  baseAmount: 5000,
})

if (result.valid) {
  console.log(result.discountAmount)
  await repo.recordSuccessfulRedemption({
    couponId: result.coupon.id,
    userId: 'user-1',
    purchaseType: 'coin',
    baseAmount: 5000,
    idempotencyKey: 'stripe-evt-123',
  })
}

For a ready-made in-memory CouponRepository (testing/onboarding), see @dhruvp13/promo-code-memory. For Payload CMS, see @dhruvp13/promo-code-adapters.

See the root README for full docs on validation rules, idempotency, and custom validators.