# Domain: Marketing (coupons, flash sales, group buying, points)

Four activity systems, all shop-scoped where merchant-facing, all resolved
server-side at checkout.

## Coupons (`modules/coupon/`)

Merchant templates (amount/threshold/window/stock) → customers claim →
redeem at checkout. Locked in id order during checkout; the discount is
computed server-side in the order currency. Coupons never combine with
activity pricing (flash sale / group buying) on the same shop order.

## Flash sales (`modules/flash_sale/`)

Merchant sessions with per-SKU items (activity price + reserved stock).
Checkout splits a line into activity-priced and normal-priced units; activity
stock is consumed via guarded decrement. A SKU rejects overlapping
flash-sale and group-buying activities.

## Group buying (`modules/group_buying/`)

Merchant activity (required members, window, group lifetime). Checkout with a
group intent takes exactly one unit at the activity price; a seat is claimed
at payment (`paid_member_count` guarded), groups open/succeed/expire.

## Points mall (`modules/points/`)

Platform-curated catalog; customers redeem with the points account
(append-only ledger, guarded points decrement), fulfillment/cancellation by
platform admins.

## Shared rules

- All money integer minor units; activity prices convert to the order
  currency server-side.
- All stock/seat counters use guarded `UPDATE … AND col >= $q`.
- Mall exposes each domain as a mock-adapter-backed live domain
  (`LIVE_PICKS`); consoles are live-only.

## Key files

See `docs/code_index/marketing.md`.