wordeck/packages/wordeck-domain/tests/fsrs.test.ts

import { describe, it, expect } from 'vitest';

import {
	buildScheduler,
	fromFsrsCard,
	gradeReview,
	newReview,
	subIndexCount,
	toFsrsCard,
} from '../src/fsrs.ts';

describe('newReview', () => {
	it('initializes with state=new and reps=0', () => {
		const r = newReview({
			userId: 'u-1',
			cardId: 'c-1',
			now: new Date('2026-05-08T10:00:00Z'),
		});
		expect(r.card_id).toBe('c-1');
		expect(r.sub_index).toBe(0);
		expect(r.user_id).toBe('u-1');
		expect(r.state).toBe('new');
		expect(r.reps).toBe(0);
		expect(r.lapses).toBe(0);
		expect(r.due).toBe('2026-05-08T10:00:00.000Z');
	});

	it('honours provided sub_index', () => {
		const r = newReview({ userId: 'u-1', cardId: 'c-1', subIndex: 2 });
		expect(r.sub_index).toBe(2);
	});
});

describe('gradeReview', () => {
	const fixedNow = new Date('2026-05-08T10:00:00Z');
	const reviewedAt = new Date('2026-05-08T10:01:00Z');
	const baseReview = newReview({
		userId: 'u-1',
		cardId: 'c-1',
		now: fixedNow,
	});

	it('Again from new keeps reps=0 increments lapses', () => {
		// Disable fuzz for deterministic test outputs
		const next = gradeReview(baseReview, 'again', reviewedAt, { enable_fuzz: false });
		expect(next.state).not.toBe('new');
		expect(next.due).not.toBe(baseReview.due);
		expect(next.reps).toBeGreaterThanOrEqual(1);
	});

	it('Easy from new transitions to a future-dated review', () => {
		const next = gradeReview(baseReview, 'easy', reviewedAt, { enable_fuzz: false });
		expect(new Date(next.due).getTime()).toBeGreaterThan(reviewedAt.getTime());
	});

	it('preserves card_id, sub_index, user_id', () => {
		const next = gradeReview(baseReview, 'good', reviewedAt, { enable_fuzz: false });
		expect(next.card_id).toBe(baseReview.card_id);
		expect(next.sub_index).toBe(baseReview.sub_index);
		expect(next.user_id).toBe(baseReview.user_id);
	});
});

describe('toFsrsCard / fromFsrsCard roundtrip', () => {
	it('roundtrips a new review without loss', () => {
		const r = newReview({ userId: 'u-1', cardId: 'c-1' });
		const fc = toFsrsCard(r);
		const back = fromFsrsCard(r, fc);
		expect(back.due).toBe(r.due);
		expect(back.stability).toBe(r.stability);
		expect(back.state).toBe(r.state);
	});
});

describe('subIndexCount', () => {
	it('basic = 1, basic-reverse = 2', () => {
		expect(subIndexCount('basic')).toBe(1);
		expect(subIndexCount('basic-reverse')).toBe(2);
	});

	it('unknown type defaults to 1', () => {
		expect(subIndexCount('unknown-future-type')).toBe(1);
	});

	it('cloze wirft — Caller muss subIndexCountForCloze nutzen', () => {
		expect(() => subIndexCount('cloze')).toThrow(/subIndexCountForCloze/);
	});
});

describe('buildScheduler', () => {
	it('builds with defaults', () => {
		const s = buildScheduler();
		expect(s).toBeDefined();
	});

	it('honours per-deck overrides', () => {
		const s = buildScheduler({ request_retention: 0.85, enable_fuzz: false });
		expect(s).toBeDefined();
	});
});