Documentation
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Overview ¶
Package couponredemption is the once-per-user redemption guard for coupons.
Each CouponRedemption is one immutable fact: "user U redeemed coupon C". The storage id is DeterministicID(couponCode, userId) and the model registers WithStringKey, so a second redeem by the same user for the same coupon resolves to the SAME row via the backend ON CONFLICT(id, kind, namespace) upsert — the guard cannot be bypassed.
This replaces a guard that queried the credit grant by Tags="coupon:CODE" while the grant was written Tags="promo,coupon:CODE": the datastore Tags= filter is exact-string, so it never matched and the same user re-minted a fresh spendable grant on every submit. A structured redemption record, keyed by (code, user), makes the check exact and forgery-proof.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
func DeterministicID ¶
DeterministicID derives the stable storage id for a (couponCode, userId) pair. Same inputs → same id → ON CONFLICT dedup at the storage layer. Prefixed so the id is human-recognizable in logs/audits.
Types ¶
type CouponRedemption ¶
type CouponRedemption struct {
mixin.Model[CouponRedemption]
CouponCode string `json:"couponCode"`
UserId string `json:"userId"`
}
CouponRedemption records that a user redeemed a coupon. One row per (CouponCode, UserId); the deterministic id makes a duplicate submit a no-op replay rather than a second mint.
func New ¶
func New(db *datastore.Datastore) *CouponRedemption
Source Files