import { describe, it, expect, vi, beforeAll, afterAll } from 'vitest';
import { getDaysDiff, getSRSDate } from '../src/utils/dateUtils.js';

describe('Date Utils', () => {
	describe('getDaysDiff', () => {
		it('should calculate difference between two dates correctly', () => {
			const d1 = '2023-01-01';
			const d2 = '2023-01-03';
			expect(getDaysDiff(d1, d2)).toBe(2);
		});

		it('should return 0 for same day', () => {
			expect(getDaysDiff('2023-01-01', '2023-01-01')).toBe(0);
		});
	});

	describe('getSRSDate', () => {
		beforeAll(() => {
			vi.useFakeTimers();
			vi.setSystemTime(new Date('2023-01-01T12:00:00Z'));
		});

		afterAll(() => {
			vi.useRealTimers();
		});

		// Helper: getSRSDate adds hours then zeroes out minutes/seconds
		const expectedDate = (hoursToAdd) => {
			const d = new Date('2023-01-01T12:00:00Z');
			d.setUTCHours(d.getUTCHours() + hoursToAdd);
			d.setUTCMinutes(0, 0, 0);
			return d.toISOString();
		};

		it('should add correct hours for levels 1-6', () => {
			expect(getSRSDate(1).toISOString()).toBe(expectedDate(4));      // 4 hours
			expect(getSRSDate(2).toISOString()).toBe(expectedDate(8));      // 8 hours
			expect(getSRSDate(3).toISOString()).toBe(expectedDate(24));     // 1 day
			expect(getSRSDate(4).toISOString()).toBe(expectedDate(48));     // 2 days
			expect(getSRSDate(5).toISOString()).toBe(expectedDate(7 * 24));  // 1 week
			expect(getSRSDate(6).toISOString()).toBe(expectedDate(14 * 24)); // 2 weeks
		});

		it('should add correct hours for levels 7-9', () => {
			expect(getSRSDate(7).toISOString()).toBe(expectedDate(30 * 24));  // 30 days
			expect(getSRSDate(8).toISOString()).toBe(expectedDate(90 * 24));  // 90 days
			expect(getSRSDate(9).toISOString()).toBe(expectedDate(180 * 24)); // 180 days
		});

		it('should return null for level 10 (burned)', () => {
			expect(getSRSDate(10)).toBeNull();
		});

		it('should default to 4 hours for unknown levels', () => {
			expect(getSRSDate(99).toISOString()).toBe(expectedDate(4));
		});
	});
});