website/src/lib/groceries.test.ts

import { describe, expect, it } from 'vitest';
import {
	bestPerStore,
	cheapest,
	formatAmount,
	formatUnitPrice,
	packLabel,
	packSizes,
	parseEuros,
	sortByPrice,
	toOffers,
	type PricedItem
} from './groceries';

const it_ = (
	id: number,
	storeId: number,
	price: number,
	unit: number,
	promo: number | null = null
): PricedItem => ({
	id,
	storeId,
	priceCents: price,
	promoPriceCents: promo,
	unitPriceCents: unit,
	promoUnitPriceCents: promo == null ? null : Math.round((unit * promo) / price),
	available: true
});

describe('grocery price helpers', () => {
	const items = [
		it_(1, 1, 119, 119),
		it_(2, 1, 165, 110),
		it_(3, 2, 115, 115),
		it_(4, 2, 200, 200, 100)
	];
	it('finds the cheapest by unit price, promos included', () => {
		const c = cheapest(items, 'unit');
		expect(c.overall).toBe(4);
		expect([...c.perStore].sort()).toEqual([2, 4]);
	});
	it('finds the cheapest by pack price', () => {
		expect(cheapest(items, 'pack').overall).toBe(4);
		expect(cheapest(items.slice(0, 3), 'pack').overall).toBe(3);
	});
	it('sorts by unit price', () => {
		expect(sortByPrice(items, 'unit').map((i) => i.id)).toEqual([4, 2, 3, 1]);
	});
	it('formats', () => {
		expect(formatUnitPrice(250, 'kg')).toMatch(/2,50\/kg$/);
		expect(formatAmount(1.98, 'l')).toBe('1,98 L');
		expect(formatUnitPrice(null, 'kg')).toBeNull();
	});
});

describe('parseEuros', () => {
	it('reads Dutch and English prices', () => {
		expect(parseEuros('1,29')).toBe(129);
		expect(parseEuros('€ 2.5')).toBe(250);
		expect(parseEuros('3')).toBe(300);
	});
	it('rejects nonsense', () => {
		expect(parseEuros('')).toBeNull();
		expect(parseEuros('0')).toBeNull();
		expect(parseEuros('1,299')).toBeNull();
		expect(parseEuros('abc')).toBeNull();
	});
});

describe('bestPerStore', () => {
	const item = (
		id: number,
		storeId: number,
		price: number,
		unit: number | null,
		promo?: number
	) => ({
		id,
		storeId,
		name: `p${id}`,
		sizeText: null,
		unit: 'kg',
		unitAmount: 1,
		promoLabel: promo ? '1+1' : null,
		url: null,
		available: true,
		priceCents: price,
		promoPriceCents: promo ?? null,
		unitPriceCents: unit,
		promoUnitPriceCents: promo ?? null
	});
	it('keeps the cheapest offer per store, cheapest store first, with the spread', () => {
		const offers = toOffers(
			[item(1, 1, 300, 300), item(2, 1, 250, 250), item(3, 2, 400, 400, 200), item(4, 3, 500, 500)],
			[
				{
					id: 9,
					itemId: null,
					storeId: 4,
					priceCents: 180,
					promo: false,
					sizeText: '1 kg',
					unit: 'kg',
					unitPriceCents: 180,
					observedOn: '2026-10-20',
					photoUrl: null,
					note: null
				}
			]
		);
		const r = bestPerStore(offers, 'unit');
		expect(r.stores.map((o) => o.key)).toEqual(['m9', 'i3', 'i2', 'i4']);
		expect(r.best?.manual?.id).toBe(9);
		expect(r.stores[1].regularCents).toBe(400);
		expect(r.spread).toEqual({ min: 180, max: 500, pct: 178 });
	});
	it('has no spread for one store', () => {
		expect(bestPerStore(toOffers([item(1, 1, 100, 100)], []), 'pack').spread).toBeNull();
	});
});

describe('packSizes', () => {
	it('lists distinct pack sizes smallest first with friendly units', () => {
		expect(
			packSizes([
				{ unitAmount: 0.8, unit: 'kg' },
				{ unitAmount: 0.22, unit: 'kg' },
				{ unitAmount: 0.45, unit: 'kg' },
				{ unitAmount: 0.22, unit: 'kg' },
				{ unitAmount: 1.5, unit: 'kg', available: false },
				{ unitAmount: null, unit: null }
			])
		).toEqual(['220 g', '450 g', '800 g']);
		expect(packLabel(1.5, 'l')).toBe('1,5 L');
		expect(packLabel(0.33, 'l')).toBe('330 ml');
		expect(packLabel(6, 'piece')).toBe('6 st');
	});
});