fix: interval upgrade / downgrade

server/tests/unit/billing/isProductUpgrade.test.ts

@@ -192,7 +192,23 @@ describe("isProductUpgrade", () => {
 			expect(isProductUpgrade({ prices1, prices2 })).toBe(true);
 		});
 
-		test("$20/mo to $200/yr = downgrade ($20/mo > $16.67/mo)", () => {
+		test("$20/mo to $500/yr = upgrade (larger interval always upgrade, even if expensive)", () => {
+			const prices1 = [
+				createFixedPrice({
+					amount: 20,
+					interval: BillingInterval.Month,
+				}),
+			];
+			const prices2 = [
+				createFixedPrice({
+					amount: 500,
+					interval: BillingInterval.Year,
+				}),
+			];
+			expect(isProductUpgrade({ prices1, prices2 })).toBe(true);
+		});
+
+		test("$20/mo to $200/yr = upgrade (larger interval always upgrade)", () => {
 			const prices1 = [
 				createFixedPrice({
 					amount: 20,
@@ -205,7 +221,7 @@ describe("isProductUpgrade", () => {
 					interval: BillingInterval.Year,
 				}),
 			];
-			expect(isProductUpgrade({ prices1, prices2 })).toBe(false);
+			expect(isProductUpgrade({ prices1, prices2 })).toBe(true);
 		});
 
 		test("$5/week to $20/mo = upgrade ($20/mo <= $20/mo)", () => {

shared/utils/productUtils/isProductUpgrade.ts

@@ -2,6 +2,10 @@ import { Decimal } from "decimal.js";
 
 import type { BillingInterval } from "../../models/productModels/intervals/billingInterval";
 import type { Price } from "../../models/productModels/priceModels/priceModels";
+import {
+	compareBillingIntervals,
+	getLargestInterval,
+} from "../intervalUtils/priceIntervalUtils";
 import { intervalToValue } from "../intervalUtils";
 import { nullish } from "../utils";
 import {
@@ -70,6 +74,17 @@ export const isProductUpgrade = ({
 		return true;
 	}
 
+	const billingInterval1 = getLargestInterval({ prices: prices1 });
+	const billingInterval2 = getLargestInterval({ prices: prices2 });
+
+	if (billingInterval1 && billingInterval2) {
+		const cmp = compareBillingIntervals({
+			configA: billingInterval1,
+			configB: billingInterval2,
+		});
+		if (cmp > 0) return true;
+	}
+
 	const total1 = getNormalizedTotal({ prices: prices1 });
 	const total2 = getNormalizedTotal({ prices: prices2 });