import { describe, it, expect } from 'vitest';
import { kstTodayIso, nextKstMidnightMs, kstTodayAsDate } from '@shared/util/kstDate.js';

describe('kstTodayIso', () => {
  it('returns KST calendar date as YYYY-MM-DD', () => {
    // 2026-05-01 12:00 UTC = 2026-05-01 21:00 KST
    expect(kstTodayIso(new Date('2026-05-01T12:00:00Z'))).toBe('2026-05-01');
  });

  it('handles UTC→KST date rollover (UTC 23:30 → KST next day 08:30)', () => {
    expect(kstTodayIso(new Date('2026-05-01T23:30:00Z'))).toBe('2026-05-02');
  });

  it('handles KST midnight exactly (UTC 15:00 = KST 00:00 next day)', () => {
    expect(kstTodayIso(new Date('2026-05-01T15:00:00Z'))).toBe('2026-05-02');
  });

  it('boundary — UTC 14:59:59 still KST 23:59:59 same day', () => {
    // KST 5/4 23:59:59 = UTC 5/4 14:59:59
    const utcDate = new Date('2026-05-04T14:59:59Z');
    expect(kstTodayIso(utcDate)).toBe('2026-05-04');
  });

  it('KST 5/5 00:30 (UTC 5/4 15:30) returns 2026-05-05', () => {
    const utcDate = new Date('2026-05-04T15:30:00Z');
    expect(kstTodayIso(utcDate)).toBe('2026-05-05');
  });
});

describe('nextKstMidnightMs', () => {
  it('returns the next KST 00:00 epoch ms (UTC 12:00 → +12h to KST midnight)', () => {
    // 2026-05-01 12:00 UTC = 2026-05-01 21:00 KST → 다음 KST 자정 = 2026-05-02 00:00 KST
    // = 2026-05-01 15:00 UTC
    const now = Date.parse('2026-05-01T12:00:00Z');
    const next = nextKstMidnightMs(now);
    expect(new Date(next).toISOString()).toBe('2026-05-01T15:00:00.000Z');
  });

  it('returns 24h-from-now-ish when called shortly after KST midnight', () => {
    // 2026-05-01 15:01 UTC = 2026-05-02 00:01 KST → 다음 KST 자정 = 2026-05-03 00:00 KST
    // = 2026-05-02 15:00 UTC (≈ 23h59m later)
    const now = Date.parse('2026-05-01T15:01:00Z');
    const next = nextKstMidnightMs(now);
    expect(new Date(next).toISOString()).toBe('2026-05-02T15:00:00.000Z');
    expect(next - now).toBeGreaterThan(23 * 60 * 60 * 1000);
    expect(next - now).toBeLessThan(24 * 60 * 60 * 1000);
  });

  it('KST 5/5 00:30 → next KST midnight = 5/6 00:00 KST = 5/5 15:00 UTC', () => {
    const utcMs = new Date('2026-05-04T15:30:00Z').getTime();
    const next = nextKstMidnightMs(utcMs);
    expect(new Date(next).toISOString()).toBe('2026-05-05T15:00:00.000Z');
  });
});

describe('kstTodayAsDate', () => {
  it('returns UTC Date at KST 00:00', () => {
    // KST 5/5 00:30 → KST 5/5 00:00 = UTC 5/4 15:00
    const utcDate = new Date('2026-05-04T15:30:00Z');
    const result = kstTodayAsDate(utcDate);
    expect(result.toISOString()).toBe('2026-05-05T00:00:00.000Z');
  });
});