cms/tests/unit/paypal-order.test.ts

import { test } from "node:test";
import assert from "node:assert/strict";
import { buildPayPalOrderItems, buildPayPalOrderRequest } from "../../src/checkout/paypal-order.ts";
import { calculateTotalProductPrice } from "../../src/checkout/pricing.ts";
import { vatDecimal, vatIncludedDecimal } from "../../src/checkout/vat.ts";

const RETURN_URL = "https://shop.example/checkout/3";
const UUID = "11111111-2222-4333-8444-555555555555";

const notebook = { id: 101, name: "Notizbuch A5 Punktraster", cover: { price: 14.9 }, pages: { price: 3 }, ruling: { price: 0 } };

// Shaped like the order the checkout controller passes to createSessionOrThrow (strapi.db.query findOne with orderDefaultParams),
// with the totals the order service computes: subtotal 17.90, total 17.90 + 4.95 = 22.85, VAT round(17.90 / 1.19 * 0.19) = 2.86.
const validOrder = (overrides = {}) => ({
	id: 4711,
	uuid: UUID,
	email: "erika@example.org",
	subtotal: 17.9,
	total: 22.85,
	VAT: 2.86,
	delivery: { id: 1, name: "DHL", price: 4.95 },
	payment: null,
	invoiceNumber: "R-12-4711",
	cart: [{ id: 1, count: 1, product: notebook }],
	deliveryAddress: "Erika Mustermann\nMusterstraße 1\n70190 Stuttgart",
	...overrides
});

// A cart of [price, count] lines with the totals the order service computes in update() (src/api/order/services/order.ts:151-173).
const orderFor = (lines: [number, number][], deliveryPrice: number | null) => {
	const cart = lines.map(([price, count], index) => ({
		id: index + 1,
		count,
		product: { id: 201 + index, name: `Produkt ${index + 1}`, cover: { price } }
	}));
	const subtotal = cart.reduce((v, p) => v + (calculateTotalProductPrice(p.product) ?? 0) * p.count, 0);
	return validOrder({
		cart,
		subtotal,
		total: Math.round((subtotal + (deliveryPrice ?? 0)) * 100) / 100,
		VAT: Math.round((subtotal / vatIncludedDecimal) * vatDecimal * 100) / 100,
		delivery: deliveryPrice === null ? null : { id: 1, name: "DHL", price: deliveryPrice }
	});
};

// Both halves in the order createSessionOrThrow runs them: what it would send to PayPal, or what it would throw.
const buildSession = (order) => {
	buildPayPalOrderItems(order);
	return buildPayPalOrderRequest(RETURN_URL, order);
};

const cents = (money) => (money ? Math.round(Number(money.value) * 100) : 0);

// PayPal rejects an order unless amount = item_total + tax_total + shipping + handling + insurance - shipping_discount - discount.
const breakdownCents = (breakdown) =>
	cents(breakdown.itemTotal) +
	cents(breakdown.taxTotal) +
	cents(breakdown.shipping) +
	cents(breakdown.handling) +
	cents(breakdown.insurance) -
	cents(breakdown.shippingDiscount) -
	cents(breakdown.discount);

const isClearError = (pattern: RegExp) => (error: unknown) => error instanceof Error && !(error instanceof TypeError) && pattern.test(error.message);

const assertNoTypeError = (build: () => unknown) => {
	try {
		build();
	} catch (error) {
		assert.ok(!(error instanceof TypeError), `threw ${error}`);
	}
};

// Characterization: what the builders do today.

test("builds the PayPal order request for a valid order", () => {
	const expected = {
		intent: "CAPTURE",
		purchaseUnits: [
			{
				referenceId: UUID,
				amount: {
					currencyCode: "EUR",
					value: "22.85",
					breakdown: {
						itemTotal: { currencyCode: "EUR", value: "15.04" },
						taxTotal: { currencyCode: "EUR", value: "2.86" },
						shipping: { currencyCode: "EUR", value: "4.95" }
					}
				},
				shipping: {
					name: { fullName: "Erika Mustermann" },
					address: { addressLine1: "Musterstraße 1", postalCode: "70190", adminArea2: "Stuttgart", countryCode: "DE" }
				},
				customId: UUID,
				invoiceId: "R-12-4711"
			}
		],
		applicationContext: { returnUrl: RETURN_URL, cancelUrl: RETURN_URL, shippingPreference: "SET_PROVIDED_ADDRESS" }
	};
	const request = buildPayPalOrderRequest(RETURN_URL, validOrder());

	assert.deepEqual(request, expected);
	// The key order is visible in the "Creating PayPal order" log line.
	assert.equal(JSON.stringify(request), JSON.stringify(expected));
});

test("sends no shipping amount when the order has no delivery method", () => {
	assert.deepEqual(buildPayPalOrderRequest(RETURN_URL, validOrder({ delivery: null, total: 17.9 })).purchaseUnits[0].amount, {
		currencyCode: "EUR",
		value: "17.90",
		breakdown: {
			itemTotal: { currencyCode: "EUR", value: "15.04" },
			taxTotal: { currencyCode: "EUR", value: "2.86" },
			shipping: undefined
		}
	});
});

test("rejects an order without a total before computing the items", () => {
	for (const total of [0, null, undefined]) {
		assert.throws(() => buildPayPalOrderItems(validOrder({ total })), { name: "Error", message: "Cart is empty or has no total" });
	}
});

test("computes one item per cart line, which is not sent to PayPal", () => {
	const order = validOrder({
		cart: [
			{ id: 1, count: 1, product: notebook },
			{ id: 2, count: 3, product: { id: 102, name: "Journaling Booklet", cover: { price: 12.5 } } }
		]
	});

	assert.deepEqual(buildPayPalOrderItems(order), [
		{
			name: "Notizbuch A5 Punktraster",
			unitAmount: { currencyCode: "EUR", value: "15.04" },
			tax: { currencyCode: "EUR", value: "2.86" },
			quantity: "1"
		},
		{
			name: "Journaling Booklet",
			unitAmount: { currencyCode: "EUR", value: "10.50" },
			tax: { currencyCode: "EUR", value: "2.00" },
			quantity: "3"
		}
	]);
});

// Known defects: these assert the correct behaviour and fail today, which the todo marks as expected.

test(
	"D1: a missing delivery address is rejected with a clear validation error",
	{ todo: "null deliveryAddress throws a TypeError — https://git.librete.ch/libretech/mp/issues/67" },
	() => {
		assert.throws(() => buildSession(validOrder({ deliveryAddress: null })), isClearError(/address/i));
	}
);

test(
	"D2: a two-line delivery address does not throw a TypeError",
	{ todo: "a two-line address throws a TypeError — https://git.librete.ch/libretech/mp/issues/67" },
	() => {
		assertNoTypeError(() => buildSession(validOrder({ deliveryAddress: "Erika Mustermann\nMusterstraße 1" })));
	}
);

test(
	"D3: a pickup whose delivery price is null is sent with shipping 0.00",
	{ todo: "delivery price null throws a TypeError — https://git.librete.ch/libretech/mp/issues/67" },
	() => {
		const order = validOrder({ delivery: { id: 2, name: "Abholung", price: null }, total: 17.9 });

		assert.deepEqual(buildSession(order).purchaseUnits[0].amount.breakdown.shipping, { currencyCode: "EUR", value: "0.00" });
	}
);

test(
	"D4: a cart line whose product was deleted is rejected with a clear error",
	{ todo: "a deleted product throws a TypeError — https://git.librete.ch/libretech/mp/issues/67" },
	() => {
		assert.throws(() => buildSession(validOrder({ cart: [{ id: 1, count: 1, product: null }] })), isClearError(/product/i));
	}
);

test(
	"D5: with a payment surcharge the breakdown still adds up to the amount",
	{ todo: "the surcharge is in the amount but not in the breakdown — https://git.librete.ch/libretech/mp/issues/67" },
	() => {
		// total = 17.90 + 4.95 shipping + 1.50 surcharge
		const { amount } = buildSession(validOrder({ payment: { id: 1, name: "PayPal", price: 1.5 }, total: 24.35 })).purchaseUnits[0];

		assert.equal(amount.value, "24.35");
		assert.equal(breakdownCents(amount.breakdown), cents(amount));
	}
);

// Not a todo: this holds today for every whole-cent subtotal (Strapi stores prices as decimal(10,2)). It guards the fixes above.
test("D6: the breakdown adds up to the amount to the cent, also for the subtotals whose net is closest to half a cent", () => {
	const carts: { lines: [number, number][]; delivery: number | null }[] = [
		{ lines: [[17.9, 1]], delivery: 4.95 },
		// subtotal 36.10000000000001 in floating point
		{
			lines: [
				[4.15, 7],
				[2.35, 3]
			],
			delivery: 4.95
		},
		// 29.03: net 24.394958, as close to a half cent as a whole-cent subtotal gets
		{
			lines: [
				[9.99, 2],
				[9.05, 1]
			],
			delivery: 4.95
		},
		// 41.18: net 34.605042, the same from above; no delivery method
		{ lines: [[20.59, 2]], delivery: null },
		{ lines: [[5.23, 1]], delivery: 4.95 },
		{ lines: [[5.48, 1]], delivery: 4.95 }
	];
	for (let cent = 1; cent <= 30000; cent++) {
		carts.push({ lines: [[cent / 100, 1]], delivery: 4.95 }, { lines: [[cent / 100, 1]], delivery: null });
	}

	const mismatches = carts.filter(({ lines, delivery }) => {
		const { amount } = buildSession(orderFor(lines, delivery)).purchaseUnits[0];
		return breakdownCents(amount.breakdown) !== cents(amount);
	});

	// Compare the count, not the array: diffing tens of thousands of entries against [] takes many GB of memory.
	assert.equal(mismatches.length, 0, `${mismatches.length} carts do not add up, e.g. ${JSON.stringify(mismatches.slice(0, 3))}`);
});