wip

shared/utils/cusEntUtils/convertCusEntUtils/cusEntsToMaxPurchase.ts

@@ -0,0 +1,59 @@
+import { Decimal } from "decimal.js";
+import {
+	cusEntToIncludedUsage,
+	type FullCusEntWithFullCusProduct,
+	isPrepaidCusEnt,
+	notNullish,
+	nullish,
+} from "../../../index.js";
+
+export const cusEntsToMaxPurchase = ({
+	cusEnts,
+	entityId,
+}: {
+	cusEnts: FullCusEntWithFullCusProduct[];
+	entityId?: string;
+}): number | null => {
+	// 1. If there's usage-based cus ent, return undefined
+	if (
+		cusEnts.some(
+			(cusEnt) =>
+				cusEnt.usage_allowed && nullish(cusEnt.entitlement.usage_limit),
+		)
+	) {
+		return null;
+	}
+
+	const hasPrepaidNoLimit = cusEnts.some(
+		(ce) =>
+			isPrepaidCusEnt({ cusEnt: ce }) && nullish(ce.entitlement.usage_limit),
+	);
+	const hasPrepaid = cusEnts.some((ce) => isPrepaidCusEnt({ cusEnt: ce }));
+	const hasUsageBased = cusEnts.some((ce) => ce.usage_allowed);
+
+	// 2. If there's usage-based cus ent, and prepaid no limit
+	if (hasUsageBased && hasPrepaidNoLimit) return null;
+
+	// 3. If there's prepaid
+	if (hasPrepaidNoLimit) return null;
+
+	// 3. If there's no prepaid and no usage-based, return undefined (free feature)
+	if (!hasPrepaid && !hasUsageBased) return null;
+
+	let maxPurchase = new Decimal(0);
+	for (const cusEnt of cusEnts) {
+		const startingBalance = cusEntToIncludedUsage({
+			cusEnt,
+			entityId,
+		});
+		const usageLimit = cusEnt.entitlement.usage_limit;
+
+		if (notNullish(usageLimit) && notNullish(startingBalance)) {
+			maxPurchase = maxPurchase.add(
+				new Decimal(usageLimit).sub(startingBalance),
+			);
+		}
+	}
+
+	return maxPurchase.toNumber();
+};