import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import * as ReviewService from '../../src/services/review.service.js';
import { User } from '../../src/models/User.js';
import { ReviewLog } from '../../src/models/ReviewLog.js';
import { StudyItem } from '../../src/models/StudyItem.js';

vi.mock('../../src/models/ReviewLog.js');
vi.mock('../../src/models/StudyItem.js');

describe('Review Service', () => {
	beforeEach(() => {
		vi.useFakeTimers();
		vi.setSystemTime(new Date('2023-01-10T00:00:00Z'));
	});

	afterEach(() => {
		vi.useRealTimers();
		vi.resetAllMocks();
	});

	describe('processReview', () => {
		const mockUser = (stats = {}) => ({
			_id: 'u1',
			stats: { ...stats },
			save: vi.fn()
		});

		const mockItem = (srs = 1) => ({
			userId: 'u1',
			wkSubjectId: 100,
			srsLevel: srs,
			stats: { correct: 0, total: 0 },
			save: vi.fn(),
			nextReview: null
		});

		it('should throw error if item not found', async () => {
			const user = mockUser();
			StudyItem.findOne.mockResolvedValue(null);

			await expect(ReviewService.processReview(user, 999, true))
				.rejects.toThrow('Item not found');

			expect(StudyItem.findOne).toHaveBeenCalledWith({
				userId: user._id,
				wkSubjectId: 999
			});
		});

		it('should handle standard success flow', async () => {
			const user = mockUser();
			delete user.stats;
			StudyItem.findOne.mockResolvedValue(mockItem());
			const res = await ReviewService.processReview(user, 100, true);
			expect(user.save).toHaveBeenCalled();
			expect(res.srsLevel).toBe(2);
		});

		it('should handle failure flow', async () => {
			const user = mockUser();
			const item = mockItem(2);
			StudyItem.findOne.mockResolvedValue(item);
			await ReviewService.processReview(user, 100, false);
			expect(item.srsLevel).toBe(1);
		});

		it('should increment streak (diff = 1)', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-09', currentStreak: 5 });
			StudyItem.findOne.mockResolvedValue(mockItem());
			await ReviewService.processReview(user, 100, true);
			expect(user.stats.currentStreak).toBe(6);
		});

		it('should maintain streak (diff = 0)', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-10', currentStreak: 5 });
			StudyItem.findOne.mockResolvedValue(mockItem());
			await ReviewService.processReview(user, 100, true);
			expect(user.stats.currentStreak).toBe(5);
		});

		it('should reset streak (diff > 1, no shield)', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-08', currentStreak: 5, lastFreezeDate: '2023-01-09' });
			StudyItem.findOne.mockResolvedValue(mockItem());
			await ReviewService.processReview(user, 100, true);
			expect(user.stats.currentStreak).toBe(1);
		});

		it('should use shield (diff = 2, shield ready)', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-08', currentStreak: 5, lastFreezeDate: '2022-01-01' });
			StudyItem.findOne.mockResolvedValue(mockItem());
			await ReviewService.processReview(user, 100, true);
			expect(user.stats.currentStreak).toBe(6);
			expect(user.stats.lastFreezeDate).toBeDefined();
		});

		it('should use shield (diff = 2) when lastFreezeDate is undefined', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-08', currentStreak: 5 });
			user.stats.lastFreezeDate = null;

			StudyItem.findOne.mockResolvedValue(mockItem());

			await ReviewService.processReview(user, 100, true);

			expect(user.stats.currentStreak).toBe(6);
			expect(user.stats.lastFreezeDate).toBeDefined();
		});

		it('should initialize item stats if missing', async () => {
			const user = mockUser();
			const item = mockItem();
			delete item.stats;
			StudyItem.findOne.mockResolvedValue(item);

			await ReviewService.processReview(user, 100, true);

			expect(item.stats).toEqual(expect.objectContaining({ correct: 1, total: 1 }));
		});

		it('should not break on time travel (diff < 0)', async () => {
			const user = mockUser({ lastStudyDate: '2023-01-11', currentStreak: 5 });
			StudyItem.findOne.mockResolvedValue(mockItem());

			await ReviewService.processReview(user, 100, true);

			expect(user.stats.lastStudyDate).toBe('2023-01-10');
			expect(user.stats.currentStreak).toBe(5);
		});
	});

	describe('getQueue', () => {
		it('should sort by priority', async () => {
			const mockFind = { sort: vi.fn().mockReturnThis(), limit: vi.fn().mockResolvedValue([]) };
			StudyItem.find.mockReturnValue(mockFind);
			await ReviewService.getQueue({ _id: 'u1' }, 10, 'priority');
			expect(mockFind.sort).toHaveBeenCalled();
		});
		it('should shuffle (default)', async () => {
			const mockFind = { limit: vi.fn().mockResolvedValue([1, 2]) };
			StudyItem.find.mockReturnValue(mockFind);
			await ReviewService.getQueue({ _id: 'u1' }, 10, 'random');
			expect(mockFind.limit).toHaveBeenCalled();
		});
	});
});