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

import { parsePreviewTime, PREVIEW_RANGE_DAYS } from './preview-time';

const NOW = new Date('2026-09-23T08:00:00Z');

describe('parsePreviewTime', () => {
  it('defaults to now when nothing is asked for', () => {
    expect(parsePreviewTime(null, NOW)).toEqual({ at: NOW, isNow: true });
  });

  it('accepts a moment in the future', () => {
    const result = parsePreviewTime('2026-09-24T08:00:00Z', NOW);
    expect(result.at.toISOString()).toBe('2026-09-24T08:00:00.000Z');
    expect(result.isNow).toBe(false);
  });

  it('accepts a local datetime as a browser sends it', () => {
    // <input type="datetime-local"> has no timezone; it is read as local time.
    expect(parsePreviewTime('2026-12-24T10:00', NOW).at.getFullYear()).toBe(2026);
  });

  it('accepts a moment in the past', () => {
    expect(parsePreviewTime('2026-09-20T08:00:00Z', NOW).isNow).toBe(false);
  });

  it('falls back to now on an unparseable value', () => {
    // Better a correct screen than a confident rendering of nonsense.
    expect(parsePreviewTime('demain matin', NOW)).toEqual({ at: NOW, isNow: true });
    expect(parsePreviewTime('', NOW)).toEqual({ at: NOW, isNow: true });
  });

  it('refuses a moment beyond the planning horizon', () => {
    const far = new Date(NOW.getTime() + (PREVIEW_RANGE_DAYS + 1) * 86_400_000);
    expect(parsePreviewTime(far.toISOString(), NOW).isNow).toBe(true);
  });

  it('accepts a moment just inside the horizon', () => {
    const edge = new Date(NOW.getTime() + (PREVIEW_RANGE_DAYS - 1) * 86_400_000);
    expect(parsePreviewTime(edge.toISOString(), NOW).isNow).toBe(false);
  });

  it('treats a moment within the minute as now', () => {
    const almost = new Date(NOW.getTime() + 30_000);
    expect(parsePreviewTime(almost.toISOString(), NOW).isNow).toBe(true);
  });
});