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

import { formatDate, formatDateRange, formatRelative } from '@/lib/utils/format-date';

describe('formatDate', () => {
  const REF = '2026-05-12T14:30:45.000Z';

  it('returns fallback for null/undefined/invalid', () => {
    expect(formatDate(null)).toBe('-');
    expect(formatDate(undefined)).toBe('-');
    expect(formatDate('not a date')).toBe('-');
    expect(formatDate(NaN)).toBe('-');
    expect(formatDate(null, 'date.medium', { fallback: 'N/A' })).toBe('N/A');
  });

  it('formats date.iso correctly in UTC', () => {
    expect(formatDate(REF, 'date.iso', { tz: 'UTC' })).toBe('2026-05-12');
  });

  it('formats date.iso correctly in a different timezone', () => {
    // 14:30 UTC = 00:30 next day in Sydney (UTC+10)
    expect(formatDate(REF, 'date.iso', { tz: 'Australia/Sydney' })).toBe('2026-05-13');
  });

  it('formats datetime.iso as full ISO string', () => {
    expect(formatDate(REF, 'datetime.iso')).toBe('2026-05-12T14:30:45.000Z');
  });

  it('formats date.medium in en-GB', () => {
    // Intl output may vary slightly across Node versions; assert it
    // contains the expected day + month + year and uses no "/".
    const out = formatDate(REF, 'date.medium', { tz: 'UTC' });
    expect(out).toMatch(/12\s/); // day
    expect(out).toContain('2026');
    expect(out.toLowerCase()).toContain('may');
  });

  it('respects timezone - datetime.short in different zones', () => {
    const ny = formatDate(REF, 'datetime.short', { tz: 'America/New_York' });
    const utc = formatDate(REF, 'datetime.short', { tz: 'UTC' });
    expect(ny).not.toBe(utc);
    expect(utc).toContain('14:30');
  });

  it('formats time-only correctly', () => {
    expect(formatDate(REF, 'time', { tz: 'UTC' })).toBe('14:30');
  });

  it('accepts Date instances + epoch ms', () => {
    const d = new Date(REF);
    expect(formatDate(d, 'date.iso', { tz: 'UTC' })).toBe('2026-05-12');
    expect(formatDate(d.getTime(), 'date.iso', { tz: 'UTC' })).toBe('2026-05-12');
  });
});

describe('formatDateRange', () => {
  it('handles missing start/end', () => {
    expect(formatDateRange(null, null)).toBe('-');
    expect(formatDateRange('2026-05-12', null)).toMatch(/→$/);
    expect(formatDateRange(null, '2026-05-12')).toMatch(/^→/);
  });

  it('collapses year when start + end are in same year', () => {
    const out = formatDateRange('2026-05-12', '2026-08-14', { tz: 'UTC' });
    // Start should NOT include year; end should.
    expect(out).toContain('→');
    expect(out).toContain('2026');
    // Crude check: there's only one "2026" in the output.
    expect((out.match(/2026/g) ?? []).length).toBe(1);
  });

  it('keeps year on both when years differ', () => {
    const out = formatDateRange('2025-12-20', '2026-01-05', { tz: 'UTC' });
    expect((out.match(/202\d/g) ?? []).length).toBe(2);
  });
});

describe('formatRelative', () => {
  const NOW = new Date('2026-05-12T12:00:00.000Z');

  it('returns "just now" for tiny deltas', () => {
    expect(formatRelative(new Date(NOW.getTime() - 5_000), { now: NOW })).toBe('just now');
  });

  it('uses minutes for past deltas under an hour', () => {
    const ten = new Date(NOW.getTime() - 10 * 60_000);
    const out = formatRelative(ten, { now: NOW });
    expect(out).toMatch(/minute/);
  });

  it('uses hours for past deltas in the same day', () => {
    const three = new Date(NOW.getTime() - 3 * 3600_000);
    const out = formatRelative(three, { now: NOW });
    expect(out).toMatch(/hour/);
  });

  it('uses days for past deltas across days', () => {
    const yesterday = new Date(NOW.getTime() - 86_400_000);
    const out = formatRelative(yesterday, { now: NOW });
    expect(out).toMatch(/day|yesterday/i);
  });

  it('uses future tense for future dates', () => {
    const tomorrow = new Date(NOW.getTime() + 86_400_000);
    const out = formatRelative(tomorrow, { now: NOW });
    expect(out).toMatch(/day|tomorrow/i);
  });

  it('returns fallback for invalid input', () => {
    expect(formatRelative(null)).toBe('-');
  });
});