@zenuinebit/pricing-rules

Promotions for a @zenuinebit/cart: buy X get Y, quantity tiers, bundles, percent off and spend thresholds. Amounts are integers in minor units.

import { createCart, addItem, computeTotals } from "@zenuinebit/cart";
import { applyPromotions } from "@zenuinebit/pricing-rules";

let cart = createCart({ currency: "INR" });
cart = addItem(cart, { sku: "TEA", name: "Tea 250g", unitPrice: 12000, quantity: 3 });

const { cart: priced, applied } = applyPromotions(cart, [
  { id: "tea-b2g1", name: "Buy 2 get 1 free", type: "buy-x-get-y", sku: "TEA", buy: 2, get: 1 },
  { id: "big-basket", name: "10% off above 500", type: "spend-threshold", minSpend: 50000, percent: 10 },
]);

applied;                       // [{ ruleId, name, amount, skus }] - show these on the receipt
computeTotals(priced);         // normal cart totals, with the promotions included

Rules | type | What it does | |---|---| | buy-x-get-y | Every buy + get units of a SKU, get are free | | quantity-tier | tiers: [{minQty, percent}], the highest tier reached applies to the line | | percent-off | Percent off listed skus, or every line if omitted | | bundle | items sold together for price; each complete set is discounted, and the saving is split exactly across lines | | spend-threshold | Cart-level percent or amount off once the cart (after line promotions) reaches minSpend |

How rules combine

• Line rules run in the order given and a line gets at most one promotion: the first rule that discounts it wins. Put your best deals first.
• Lines that already have a manual discount are left alone.
• Spend-threshold rules run last, on what is left after line promotions.
• Calling applyPromotions again starts from scratch, so it is safe to re-run after the cart changes. The input cart is never changed.
• Promotions are stored as discounts with a promo:<id> code, so they show up in the normal cart totals.

Not included: coupon codes and usage limits, date ranges, customer groups, and stacking several promotions on one line. Check those in your app before passing the rules in.