/**
 * Copyright (c) Nicolas Gallagher.
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */
import { canUseDOM } from '@tamagui/react-native-web-internals'

export type ColorSchemeName = 'light' | 'dark'

export type AppearancePreferences = {
  colorScheme: ColorSchemeName
}

type AppearanceListener = (preferences: AppearancePreferences) => void
type DOMAppearanceListener = (ev: MediaQueryListEvent) => any

function getQuery(): MediaQueryList | null {
  return canUseDOM && window.matchMedia != null
    ? window.matchMedia('(prefers-color-scheme: dark)')
    : null
}

const query = getQuery()
const listenerMapping = new WeakMap<AppearanceListener, DOMAppearanceListener>()

const Appearance = {
  getColorScheme(): ColorSchemeName {
    return query && query.matches ? 'dark' : 'light'
  },

  addChangeListener(listener: AppearanceListener): {
    remove: () => void
  } {
    let mappedListener = listenerMapping.get(listener)
    if (!mappedListener) {
      mappedListener = ({ matches }: MediaQueryListEvent) => {
        listener({ colorScheme: matches ? 'dark' : 'light' })
      }
      listenerMapping.set(listener, mappedListener)
    }
    if (query) {
      query.addListener(mappedListener)
    }

    function remove(): void {
      const mappedListener = listenerMapping.get(listener)
      if (query && mappedListener) {
        query.removeListener(mappedListener)
      }
      listenerMapping.delete(listener)
    }

    return { remove }
  },
}

export default Appearance