import { afterEach, describe, expect, it } from 'vitest'
import { applyColorScheme, DARK_QUERY } from '../../src/app/theme'
import { fakeMedia } from '../helpers'

afterEach(() => {
  document.documentElement.classList.remove('dark')
})

describe('applyColorScheme (A6: system preference only)', () => {
  it('sets .dark from prefers-color-scheme and follows changes until unsubscribed', () => {
    const media = fakeMedia({ [DARK_QUERY]: true })
    const stop = applyColorScheme()
    expect(document.documentElement.classList.contains('dark')).toBe(true)
    expect(media.listeners(DARK_QUERY)).toBe(1)

    media.change(DARK_QUERY, false)
    expect(document.documentElement.classList.contains('dark')).toBe(false)
    media.change(DARK_QUERY, true)
    expect(document.documentElement.classList.contains('dark')).toBe(true)

    stop()
    expect(media.listeners(DARK_QUERY)).toBe(0)
    media.change(DARK_QUERY, false)
    expect(document.documentElement.classList.contains('dark')).toBe(true)
  })

  it('stays light without matchMedia', () => {
    document.documentElement.classList.add('dark')
    const win = { document } as unknown as Window
    const stop = applyColorScheme(win)
    expect(document.documentElement.classList.contains('dark')).toBe(false)
    expect(stop()).toBeUndefined()
  })
})