FA-60548 / Loyalty points ledgers / Member archive

Promotion stacking rules: best non-stackable choice · case 03

The first listed non-stackable promo applies even when a richer one exists.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input {base, promos:[{id,kind,value,stackable,cap}]}. A multiplier promo (value in percent) gives floor(base*(value-100)/100) extra; a fixed promo gives value. Each extra is capped at cap when cap > 0. All stackable extras apply; of the non-stackable promos only the single best capped extra applies (ties to the lower id), in addition to the stackable ones. Return {bonus, applied ids sorted}.

Why this case matters

Member point balances, statements and the program liability depend on this ledger rule.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
mixed promos	`{"applied": [1, 2], "bonus": 1303}`	`{"applied": [1, 3], "bonus": 1504}`	Failed

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