import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
import { cn, formatDate, formatFullDate, getInitials, getRelativeTime, getDaysUntil } from './utils';

describe('cn', () => {
  it('merges class names', () => {
    expect(cn('foo', 'bar')).toBe('foo bar');
  });

  it('handles conditional classes', () => {
    expect(cn('base', false && 'hidden', 'visible')).toBe('base visible');
  });

  it('merges tailwind conflicts', () => {
    expect(cn('px-4', 'px-2')).toBe('px-2');
  });
});

describe('formatDate', () => {
  beforeEach(() => {
    vi.useFakeTimers();
    vi.setSystemTime(new Date('2026-01-28T12:00:00Z'));
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  it('returns empty string for undefined', () => {
    expect(formatDate(undefined)).toBe('');
  });

  it('returns "Today" for today\'s date', () => {
    expect(formatDate('2026-01-28')).toBe('Today');
  });

  it('returns "Tomorrow" for tomorrow\'s date', () => {
    expect(formatDate('2026-01-29')).toBe('Tomorrow');
  });

  it('returns "Yesterday" for yesterday\'s date', () => {
    expect(formatDate('2026-01-27')).toBe('Yesterday');
  });

  it('returns short format for same year', () => {
    const result = formatDate('2026-03-15');
    expect(result).toBe('Mar 15');
  });

  it('returns full format for different year', () => {
    const result = formatDate('2025-03-15');
    expect(result).toBe('Mar 15, 2025');
  });
});

describe('formatFullDate', () => {
  it('returns empty string for undefined', () => {
    expect(formatFullDate(undefined)).toBe('');
  });

  it('returns full formatted date', () => {
    const result = formatFullDate('2026-01-28');
    expect(result).toContain('January');
    expect(result).toContain('28');
    expect(result).toContain('2026');
  });
});

describe('getInitials', () => {
  it('returns initials from first and last name', () => {
    expect(getInitials('John', 'Doe')).toBe('JD');
  });

  it('handles empty strings', () => {
    expect(getInitials('', '')).toBe('');
  });

  it('handles single name', () => {
    expect(getInitials('Alice', '')).toBe('A');
  });
});

describe('getRelativeTime', () => {
  beforeEach(() => {
    vi.useFakeTimers();
    vi.setSystemTime(new Date('2026-01-28T12:00:00Z'));
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  it('returns "Never" for undefined', () => {
    expect(getRelativeTime(undefined)).toBe('Never');
  });

  it('returns "Today" for today', () => {
    expect(getRelativeTime('2026-01-28T10:00:00Z')).toBe('Today');
  });

  it('returns "Yesterday" for yesterday', () => {
    expect(getRelativeTime('2026-01-27T10:00:00Z')).toBe('Yesterday');
  });

  it('returns days ago for recent dates', () => {
    expect(getRelativeTime('2026-01-25T10:00:00Z')).toBe('3 days ago');
  });

  it('returns weeks ago', () => {
    expect(getRelativeTime('2026-01-14T10:00:00Z')).toBe('2 weeks ago');
  });

  it('returns months ago', () => {
    expect(getRelativeTime('2025-11-28T10:00:00Z')).toBe('2 months ago');
  });
});

describe('getDaysUntil', () => {
  beforeEach(() => {
    vi.useFakeTimers();
    vi.setSystemTime(new Date('2026-01-28T12:00:00Z'));
  });

  afterEach(() => {
    vi.useRealTimers();
  });

  it('returns 0 for today', () => {
    expect(getDaysUntil('2026-01-28')).toBe(0);
  });

  it('returns positive for future dates', () => {
    expect(getDaysUntil('2026-02-01')).toBe(4);
  });

  it('projects past dates to next occurrence', () => {
    // Jan 15 already passed, should project to next year
    const days = getDaysUntil('2025-01-15');
    expect(days).toBeGreaterThan(300); // ~352 days to Jan 15 2027
  });
});