import {
  consumePendingScrollRestore,
  scrollDocumentTo,
  scrollDocumentToTop,
  shouldUseSiteRouteVeil
} from '../lib/site-route-transition.js'

const SITE_ROUTE_VEIL_CLASS = 'site-page-veil'

/**
 * 공개 페이지 이동 시 전환 베일을 표시하고, 베일 뒤에서 스크롤을 정리한 뒤 새 화면을 드러낸다.
 */
export default defineNuxtPlugin((nuxtApp) => {
  const router = useRouter()
  const isSitePageVeiled = useState('site-page-veil', () => false)

  /** @type {boolean} */
  let activeVeilNavigation = false

  /**
   * 전환 베일을 즉시 표시한다.
   * @returns {void}
   */
  const showRouteVeil = () => {
    if (document.documentElement.classList.contains(SITE_ROUTE_VEIL_CLASS)) {
      return
    }

    activeVeilNavigation = true
    isSitePageVeiled.value = true
    document.documentElement.classList.add(SITE_ROUTE_VEIL_CLASS)
  }

  /**
   * 전환 베일을 즉시 숨긴다.
   * @returns {void}
   */
  const hideRouteVeil = () => {
    activeVeilNavigation = false
    isSitePageVeiled.value = false
    document.documentElement.classList.remove(SITE_ROUTE_VEIL_CLASS)
  }

  /**
   * 내부 링크 클릭이 라우터보다 먼저 베일을 덮도록 한다.
   * @param {MouseEvent} event - 클릭 이벤트
   * @returns {void}
   */
  const handleInternalLinkCapture = (event) => {
    if (event.defaultPrevented || event.button !== 0) {
      return
    }

    if (event.metaKey || event.ctrlKey || event.shiftKey || event.altKey) {
      return
    }

    const target = event.target
    if (!(target instanceof Element)) {
      return
    }

    const anchor = target.closest('a')
    if (!anchor || anchor.target === '_blank' || anchor.hasAttribute('download')) {
      return
    }

    const href = anchor.getAttribute('href')
    if (!href || href.startsWith('#') || href.startsWith('mailto:') || href.startsWith('tel:')) {
      return
    }

    let url = null
    try {
      url = new URL(anchor.href, window.location.origin)
    } catch {
      return
    }

    if (url.origin !== window.location.origin) {
      return
    }

    const currentPath = router.currentRoute.value.path
    if (!shouldUseSiteRouteVeil(url.pathname) && !shouldUseSiteRouteVeil(currentPath)) {
      return
    }

    if (url.pathname === currentPath && !url.hash) {
      return
    }

    showRouteVeil()
  }

  /**
   * 페이지 렌더 완료 후 스크롤을 맞추고 베일을 해제한다.
   * @returns {Promise<void>}
   */
  const finishRouteTransition = async () => {
    if (!activeVeilNavigation) {
      return
    }

    const route = router.currentRoute.value
    const restore = consumePendingScrollRestore()

    if (restore) {
      scrollDocumentTo(restore)
    } else if (!route.hash) {
      scrollDocumentToTop()
    }

    await new Promise((resolve) => requestAnimationFrame(resolve))
    await new Promise((resolve) => requestAnimationFrame(resolve))

    if (restore) {
      scrollDocumentTo(restore)
    } else if (!route.hash) {
      scrollDocumentToTop()
    }

    await new Promise((resolve) => setTimeout(resolve, 48))

    hideRouteVeil()
  }

  if (import.meta.client && 'scrollRestoration' in window.history) {
    window.history.scrollRestoration = 'manual'
  }

  document.addEventListener('click', handleInternalLinkCapture, true)

  router.beforeEach((to, from) => {
    if (to.fullPath === from.fullPath) {
      return
    }

    if (!shouldUseSiteRouteVeil(to.path) && !shouldUseSiteRouteVeil(from.path)) {
      return
    }

    showRouteVeil()
  })

  router.onError(() => {
    hideRouteVeil()
  })

  nuxtApp.hook('page:finish', () => {
    finishRouteTransition()
  })

  nuxtApp.hook('app:error', () => {
    hideRouteVeil()
  })
})