fuzzyworld

when-am-i / files / src / utils / lanes.test.ts

lanes.test.ts

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ba77fd91 2026-06-19 Pavel Safronov1import { describe, it, expect } from 'vitest';
2import { assignLanes } from './lanes';
3
4interface Span { start: number; end: number; }
5const lane = (spans: Span[]) =>
6 assignLanes(spans, (s) => s.start, (s) => s.end);
7
8describe('assignLanes', () => {
9 it('puts non-overlapping, adjacent intervals in the same lane', () => {
10 const { lanes, count } = lane([
11 { start: 1630, end: 1752 },
12 { start: 1752, end: Infinity }, // half-open: shares the lane
13 ]);
14 expect(count).toBe(1);
15 expect(lanes.map((l) => l.lane)).toEqual([0, 0]);
16 });
17
18 it('puts overlapping intervals in separate lanes', () => {
19 const { lanes, count } = lane([
20 { start: -Infinity, end: Infinity }, // spans everything
21 { start: 1630, end: 1752 },
22 { start: 1752, end: Infinity },
23 ]);
24 expect(count).toBe(2);
25 // The all-spanning interval gets its own lane; the two adjacent ones share the other.
26 const byOrder = lanes.sort((a, b) => a.item.start - b.item.start).map((l) => l.lane);
27 expect(byOrder[0]).not.toBe(byOrder[1]); // spanning vs 1630
28 expect(byOrder[1]).toBe(byOrder[2]); // 1630 and 1752 share
29 });
30
31 it('opens a third lane when three intervals overlap at once', () => {
32 const { count } = lane([
33 { start: 0, end: 10 },
34 { start: 5, end: 15 },
35 { start: 8, end: 20 },
36 ]);
37 expect(count).toBe(3);
38 });
39});