Coupons

What it does

A coupon is a small, reusable discount rule: a code, a type (fixed rupiah amount or percentage), and an amount. Staff create and manage coupons from a simple admin list, the same way they manage products or suppliers.

The interesting part isn't the coupon itself — it's where staff choose to apply it. On the transaction screen, every coupon can be attached in either of two places: to the whole bill, discounting the total, or to a single line item, discounting just that one item's subtotal. Nothing about the coupon changes between the two — staff simply pick the placement that fits the situation.

Why it matters

Real discounts rarely apply evenly to everyone in a group. A table with three board-game tickets might have one student who qualifies for a discount and two friends who pay full price — that's a per-item coupon. A promotion for "Rp 15,000 off any order" is a per-bill coupon. Rather than building a separate feature for every promotion the cafe invents, one coupon model with a placement choice covers both, and any future one-off deal a manager comes up with, without an engineer being involved.

Screenshot

Key capabilities

• Two coupon types — fixed knocks a flat rupiah amount off; percentage takes a percentage off, rounded to the nearest Rp 500 for clean cash handling.
• Simple admin CRUD — create, view, and edit coupons by code, type, and amount; no special casing per promotion.
• Whole-bill or per-line placement — the same coupon list is offered both at the transaction level and next to each line item; staff decide which fits.
• At most one coupon per line — keeps the math and the screen predictable (no stacking within a single item in this version).
• Independent per-ticket discounts — in a checkout with several rental tickets, each ticket can carry its own coupon (or none), so only the tickets that qualify are discounted.
• Safe math — a fixed discount is clamped so it never exceeds the amount it's being applied to; a line or a bill can be discounted to zero, never below.
• Real examples in use — the cafe's rental promotions run entirely on this mechanism:
  • FREE 1 HOUR — fixed, Rp 15,000 off a ticket.
  • FREE 2 HOUR — fixed, Rp 30,000 off a ticket.
  • STUDENT DISCOUNT — percentage, 40% off a single ticket.

For engineers

• Screens: libs/ui/src/presentation/screens/CouponListScreen.tsx, CouponCreateScreen.tsx, CouponUpdateScreen.tsx
• Entity: libs/ui/src/domain/entities/Coupon.ts
• Backend application math: apps/api/domain/transaction_usecase.go
• Design rationale for per-item placement: docs/prd-rental-coupons.md