fuzzyworld

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

dateRange.test.ts

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8fa8f3cb 2026-06-21 Pavel Safronov1import { describe, it, expect } from 'vitest';
2import { deriveMinYear } from './dateRange';
3import type { CalendarRegion, Era } from '../types';
4
5const WORLD_GEO = { type: 'Polygon' as const, coordinates: [[[0, 0], [1, 0], [1, 1], [0, 0]] as [number, number][]] };
6
7function regionWith(eras: Era[]): CalendarRegion {
8 return { region: { name: 'Test', geo: WORLD_GEO }, eras };
9}
10
11describe('deriveMinYear', () => {
12 it('falls back to 2000 BCE when no era has a dated start', () => {
13 const regions = [regionWith([{ name: 'Open', start: null, end: null, calendar: 'Gregorian' }])];
14 expect(deriveMinYear(regions, 2026)).toBe(-1999);
15 });
16
17 it('uses the oldest dated start across all regions, minus a 10% margin', () => {
18 const regions = [
19 regionWith([{ name: 'A', start: '1700-01-01', end: null, calendar: 'Gregorian' }]),
20 regionWith([{ name: 'B', start: '-0036-01-01', end: null, calendar: 'Maya Long Count' }]),
21 ];
22 // oldest = -36; span to 2026 = 2062; margin = 206.2 → floor(-36 - 206.2) = -243
23 expect(deriveMinYear(regions, 2026)).toBe(-243);
24 });
25
26 it('ignores null-start eras even when other eras in the same region are dated', () => {
27 const regions = [
28 regionWith([
29 { name: 'Open', start: null, end: '1000-01-01', calendar: 'Hebrew' },
30 { name: 'Dated', start: '500-01-01', end: null, calendar: 'Gregorian' },
31 ]),
32 ];
33 // oldest dated = 500; span to 2026 = 1526; margin = 152.6 → floor(500 - 152.6) = 347
34 expect(deriveMinYear(regions, 2026)).toBe(347);
35 });
36});