import { afterEach, describe, expect, it, vi } from 'vitest'
import {
  THEME_STORAGE_KEY,
  applyResolvedTheme,
  applyThemeFromPreference,
  isThemePreference,
  readThemePreference,
  resolveTheme,
  writeThemePreference,
} from './theme'

function createMemoryStorage(initial: Record<string, string> = {}) {
  const store = new Map(Object.entries(initial))
  return {
    getItem(key: string) {
      return store.has(key) ? store.get(key)! : null
    },
    setItem(key: string, value: string) {
      store.set(key, value)
    },
  }
}

describe('isThemePreference', () => {
  it('accepts light, dark, and auto', () => {
    expect(isThemePreference('light')).toBe(true)
    expect(isThemePreference('dark')).toBe(true)
    expect(isThemePreference('auto')).toBe(true)
  })

  it('rejects invalid values', () => {
    expect(isThemePreference('mocha')).toBe(false)
    expect(isThemePreference('')).toBe(false)
  })
})

describe('readThemePreference', () => {
  it('defaults to auto when nothing is stored', () => {
    expect(readThemePreference(createMemoryStorage())).toBe('auto')
  })

  it('returns a stored preference', () => {
    const storage = createMemoryStorage({ [THEME_STORAGE_KEY]: 'dark' })
    expect(readThemePreference(storage)).toBe('dark')
  })

  it('falls back to auto for invalid stored values', () => {
    const storage = createMemoryStorage({ [THEME_STORAGE_KEY]: 'neon' })
    expect(readThemePreference(storage)).toBe('auto')
  })
})

describe('writeThemePreference', () => {
  it('persists the preference', () => {
    const storage = createMemoryStorage()
    writeThemePreference('light', storage)
    expect(storage.getItem(THEME_STORAGE_KEY)).toBe('light')
  })
})

describe('resolveTheme', () => {
  it('maps light to latte and dark to mocha', () => {
    expect(resolveTheme('light', true)).toBe('latte')
    expect(resolveTheme('dark', false)).toBe('mocha')
  })

  it('maps auto from the browser preference', () => {
    expect(resolveTheme('auto', true)).toBe('mocha')
    expect(resolveTheme('auto', false)).toBe('latte')
  })
})

describe('applyResolvedTheme', () => {
  afterEach(() => {
    delete document.documentElement.dataset.theme
  })

  it('sets data-theme on the root element', () => {
    applyResolvedTheme('mocha')
    expect(document.documentElement.dataset.theme).toBe('mocha')
  })
})

describe('applyThemeFromPreference', () => {
  afterEach(() => {
    delete document.documentElement.dataset.theme
    vi.restoreAllMocks()
  })

  it('applies the resolved theme from preference and system preference', () => {
    const resolved = applyThemeFromPreference('auto', true)
    expect(resolved).toBe('mocha')
    expect(document.documentElement.dataset.theme).toBe('mocha')
  })
})