// @vitest-environment jsdom
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
import { Context } from 'cordis'
import type { ThemeSnapshot } from '@deepseek-ai/dsh-client-ui-theme/client'
import { STORAGE_KEY, ThemeService } from '@deepseek-ai/dsh-client-ui-theme/client'

const make = (): { ctx: Context; theme: ThemeService; events: ThemeSnapshot[] } => {
  const ctx = new Context()
  const events: ThemeSnapshot[] = []
  ctx.on('theme/change', (snapshot) => { events.push(snapshot) })
  return { ctx, theme: new ThemeService(ctx), events }
}

describe('ThemeService', () => {
  beforeEach(() => {
    localStorage.clear()
  })

  it('defaults to the system preference resolved against prefers-color-scheme', () => {
    const { theme } = make()
    const snapshot = theme.getTheme()
    expect(snapshot.preference).toBe('system')
    // jsdom matchMedia is absent; system resolves to light.
    expect(snapshot.active.id).toBe('light')
    expect(snapshot.active.colorScheme).toBe('light')
    expect(snapshot.themes.map(t => t.id)).toEqual(['light', 'dark'])
  })

  it('setTheme switches, persists, republishes, and keeps DOM untouched', () => {
    const { theme, events } = make()
    theme.setTheme('dark')
    expect(theme.getTheme().preference).toBe('dark')
    expect(theme.getTheme().active.colorScheme).toBe('dark')
    expect(localStorage.getItem(STORAGE_KEY)).toBe('dark')
    expect(events).toHaveLength(1)
    expect(events[0]).toBe(theme.getTheme())
    // The service never touches presentation state.
    expect(document.body.hasAttribute('data-ds-dark-theme')).toBe(false)
    // Same-value set is a no-op (no extra event).
    theme.setTheme('dark')
    expect(events).toHaveLength(1)
  })

  it('restores a persisted preference and falls back on garbage', () => {
    localStorage.setItem(STORAGE_KEY, 'dark')
    expect(make().theme.getTheme().preference).toBe('dark')
    localStorage.setItem(STORAGE_KEY, 'sepia')
    expect(make().theme.getTheme().preference).toBe('system')
  })

  it('throws on unknown setTheme ids, duplicate registration, and the system id', () => {
    const { theme } = make()
    expect(() => { theme.setTheme('sepia') }).toThrow('not registered')
    expect(() => theme.register({ id: 'light', colorScheme: 'light', tokens: {} })).toThrow('already registered')
    expect(() => theme.register({ id: 'system', colorScheme: 'light', tokens: {} })).toThrow('preference')
  })

  it('registered themes join the snapshot; disposing the active one resets to default', () => {
    const { theme, events } = make()
    const dispose = theme.register({ id: 'sepia', colorScheme: 'light', tokens: { '--dsw-alias-bg-base': 'red' } })
    expect(theme.getTheme().themes.map(t => t.id)).toEqual(['light', 'dark', 'sepia'])
    theme.setTheme('sepia')
    expect(theme.getTheme().active.tokens['--dsw-alias-bg-base']).toBe('red')
    dispose()
    expect(theme.getTheme().preference).toBe('system')
    expect(theme.getTheme().themes.map(t => t.id)).toEqual(['light', 'dark'])
    expect(localStorage.getItem(STORAGE_KEY)).toBe('system')
    // register + set + dispose = three publishes; disposer is idempotent.
    expect(events.length).toBe(3)
    dispose()
    expect(events.length).toBe(3)
  })

  it('disposing an inactive theme keeps the active preference', () => {
    const { theme } = make()
    const dispose = theme.register({ id: 'sepia', colorScheme: 'light', tokens: {} })
    theme.setTheme('dark')
    dispose()
    expect(theme.getTheme().preference).toBe('dark')
  })

  it('revision increases monotonically across every publish', () => {
    const { theme, events } = make()
    theme.setTheme('dark')
    theme.setTheme('light')
    const dispose = theme.register({ id: 'sepia', colorScheme: 'dark', tokens: {} })
    dispose()
    expect(events.map(e => e.revision)).toEqual([1, 2, 3, 4])
  })

  it('runs without localStorage (node boots): defaults on read, no-op on write', () => {
    vi.stubGlobal('localStorage', undefined)
    try {
      const { theme } = make()
      expect(theme.getTheme().preference).toBe('system')
      theme.setTheme('dark')
      expect(theme.getTheme().preference).toBe('dark')
    } finally {
      vi.unstubAllGlobals()
    }
  })

  describe('prefers-color-scheme resolution (stubbed matchMedia)', () => {
    type Listener = () => void
    const stubMedia = (initialMatches: boolean) => {
      const listeners = new Set<Listener>()
      const media = {
        matches: initialMatches,
        addEventListener: (_: 'change', fn: Listener) => { listeners.add(fn) },
        removeEventListener: (_: 'change', fn: Listener) => { listeners.delete(fn) },
        flip() {
          this.matches = !this.matches
          for (const fn of listeners) fn()
        },
        listenerCount: () => listeners.size,
      }
      vi.stubGlobal('matchMedia', () => media)
      return media
    }

    afterEach(() => { vi.unstubAllGlobals() })

    it('system resolves against the media query and follows OS flips', () => {
      const media = stubMedia(true)
      const { theme, events } = make()
      expect(theme.getTheme().preference).toBe('system')
      expect(theme.getTheme().active.id).toBe('dark')
      media.flip()
      expect(theme.getTheme().active.id).toBe('light')
      expect(events).toHaveLength(1)
    })

    it('OS flips do not republish while a concrete preference is set', () => {
      const media = stubMedia(false)
      const { theme, events } = make()
      theme.setTheme('light')
      expect(events).toHaveLength(1)
      media.flip()
      expect(events).toHaveLength(1)
      expect(theme.getTheme().active.id).toBe('light')
    })

    it('context dispose releases the media listener', async () => {
      const media = stubMedia(false)
      const { ctx } = make()
      expect(media.listenerCount()).toBe(1)
      await ctx.fiber.dispose()
      expect(media.listenerCount()).toBe(0)
    })
  })
})
