Templates belong to a shop; claiming copies their terms into a customer-owned
snapshot so a later edit or disable cannot rewrite a held coupon. Claim stock
is taken with a guarded decrement after locking the template, and a unique
(user, template) index makes a duplicate claim a 409. Deleting a template
leaves claimed snapshots standing via ON DELETE SET NULL.
Checkout accepts at most one owned coupon per generated shop order, locks the
selected coupons by primary key after the SKU locks, and resolves eligibility
and the discount server-side (ownership, shop, status, window, converted
threshold). The realized discount and coupon id land on the order, and a
pending-payment cancellation restores the coupon in the same transaction as
stock.
The shared contract gains the coupon types, claim/list/manage methods, and the
checkout coupon map; the fixed-data adapter implements the same surface.
Surfaces (shop-admin management, mall coupon pages, checkout selection) and
seeding still follow in tasks 3.1-4.2.
Prevent oversell by conditioning stock updates and locking SKUs in primary-key order, and record the same concurrent-counter rule in the API spec and agent guide.
Co-authored-by: Cursor <cursoragent@cursor.com>
Keep the REST contract; move domain logic out of route files so checkout, fulfillment, and identity can be reused across customer, shop, and admin surfaces.
Co-authored-by: Cursor <cursoragent@cursor.com>
james
Chengdong ZhangandCursor