import { describe, it, expect, beforeEach, vi } from 'vitest';
import { applyStoredTheme, toggleTheme } from './theme';

// Minimal DOM shim — vitest runs in node
const makeHtml = () => ({ dataset: {} as Record<string, string> });

let html: ReturnType<typeof makeHtml>;
let store: Record<string, string>;

beforeEach(() => {
  html = makeHtml();
  store = {};
  vi.stubGlobal('document', { documentElement: html });
  vi.stubGlobal('localStorage', {
    getItem: (k: string) => store[k] ?? null,
    setItem: (k: string, v: string) => { store[k] = v; },
    removeItem: (k: string) => { delete store[k]; },
  });
});

describe('applyStoredTheme', () => {
  it('sets data-theme=light when localStorage has light', () => {
    store['musehub-theme'] = 'light';
    applyStoredTheme();
    expect(html.dataset['theme']).toBe('light');
  });

  it('does nothing when localStorage has dark', () => {
    store['musehub-theme'] = 'dark';
    applyStoredTheme();
    expect(html.dataset['theme']).toBeUndefined();
  });

  it('does nothing when localStorage is empty', () => {
    applyStoredTheme();
    expect(html.dataset['theme']).toBeUndefined();
  });
});

describe('toggleTheme', () => {
  it('dark → light: sets data-theme and saves light', () => {
    toggleTheme();
    expect(html.dataset['theme']).toBe('light');
    expect(store['musehub-theme']).toBe('light');
  });

  it('light → dark: removes data-theme and saves dark', () => {
    html.dataset['theme'] = 'light';
    toggleTheme();
    expect(html.dataset['theme']).toBeUndefined();
    expect(store['musehub-theme']).toBe('dark');
  });

  it('round-trips correctly', () => {
    toggleTheme(); // → light
    toggleTheme(); // → dark
    expect(html.dataset['theme']).toBeUndefined();
    expect(store['musehub-theme']).toBe('dark');
  });
});