import { animate, stagger } from 'motion-v'
import type { DOMKeyframesDefinition, AnimationOptions } from 'motion-v'

// 상수 정의
const ANIMATION_CONFIG = {
  initial: {
    opacity: 0,
    translateY: '40px',
  },
  target: {
    opacity: 1,
    y: 0,
  },
  stagger: 0.1,
  duration: 0.6,
  easing: 'ease',
} as const

const INTERSECTION_CONFIG = {
  threshold: 0.2,
} as const

const RETRY_DELAYS = [0, 100, 300] as const

// 타입 정의
type SectionElement = HTMLElement & { tagName: 'SECTION' }

export default defineNuxtPlugin(nuxtApp => {
  // 전역 상태 관리
  const animatedItems = new Set<HTMLElement>()
  const sectionObservers = new Map<SectionElement, IntersectionObserver>()
  const sectionItems = new Map<SectionElement, Set<HTMLElement>>()

  /**
   * 섹션의 motion-item들을 애니메이션
   */
  const animateSectionItems = (section: SectionElement): void => {
    const items = sectionItems.get(section)
    if (!items?.size) return

    const newItems = Array.from(items).filter(item => !animatedItems.has(item))
    if (!newItems.length) return

    // 애니메이션 실행
    newItems.forEach(item => animatedItems.add(item))

    animate(
      newItems,
      ANIMATION_CONFIG.target as DOMKeyframesDefinition,
      {
        delay: stagger(ANIMATION_CONFIG.stagger),
        duration: ANIMATION_CONFIG.duration,
        easing: ANIMATION_CONFIG.easing,
      } as AnimationOptions
    )
  }

  /**
   * 섹션이 viewport에 있는지 확인
   */
  const isSectionInViewport = (section: SectionElement): boolean => {
    const rect = section.getBoundingClientRect()
    const windowHeight =
      window.innerHeight || document.documentElement.clientHeight
    const visibleHeight =
      Math.min(rect.bottom, windowHeight) - Math.max(rect.top, 0)
    const sectionHeight = rect.height

    return visibleHeight / sectionHeight >= INTERSECTION_CONFIG.threshold
  }

  /**
   * 섹션에 IntersectionObserver 등록
   */
  const observeSection = (section: SectionElement): void => {
    if (sectionObservers.has(section)) return

    const observer = new IntersectionObserver(entries => {
      for (const entry of entries) {
        if (entry.isIntersecting) {
          animateSectionItems(section)
        }
      }
    }, INTERSECTION_CONFIG)

    observer.observe(section)
    sectionObservers.set(section, observer)
  }

  /**
   * 섹션에 아이템 등록 및 초기 애니메이션 체크
   */
  const registerItem = (el: HTMLElement, section: SectionElement): void => {
    // 섹션의 아이템 목록에 추가
    if (!sectionItems.has(section)) {
      sectionItems.set(section, new Set())
      observeSection(section)
    }
    sectionItems.get(section)!.add(el)

    // 이미 viewport에 있는 경우 즉시 체크 (여러 번 체크)
    if (!isSectionInViewport(section)) return

    // 즉시 실행 및 재확인
    for (const delay of RETRY_DELAYS) {
      if (delay === 0) {
        requestAnimationFrame(() => {
          if (isSectionInViewport(section)) {
            animateSectionItems(section)
          }
        })
      } else {
        setTimeout(() => {
          if (isSectionInViewport(section)) {
            animateSectionItems(section)
          }
        }, delay)
      }
    }
  }

  /**
   * 섹션에서 아이템 제거 및 정리
   */
  const unregisterItem = (el: HTMLElement, section: SectionElement): void => {
    const items = sectionItems.get(section)
    if (!items) return

    items.delete(el)
    animatedItems.delete(el)

    // 섹션에 아이템이 없으면 observer 정리
    if (items.size === 0) {
      const observer = sectionObservers.get(section)
      observer?.disconnect()
      sectionObservers.delete(section)
      sectionItems.delete(section)
    }
  }

  /**
   * 초기 스타일 설정
   */
  const setInitialStyles = (el: HTMLElement): void => {
    el.style.opacity = ANIMATION_CONFIG.initial.opacity.toString()
    el.style.transform = `translateY(${ANIMATION_CONFIG.initial.translateY})`
  }

  /**
   * 가장 가까운 section 찾기
   */
  const findSection = (el: HTMLElement): SectionElement | null => {
    const section = el.closest('section')
    if (!section) {
      if (import.meta.dev) {
        // eslint-disable-next-line no-console
        console.warn('[motion-stagger] No section found for element:', el)
      }
      return null
    }
    return section as SectionElement
  }

  // v-motion-stagger 디렉티브
  nuxtApp.vueApp.directive('motion-stagger', {
    mounted(el: HTMLElement) {
      setInitialStyles(el)

      const section = findSection(el)
      if (!section) return

      registerItem(el, section)
    },

    unmounted(el: HTMLElement) {
      const section = el.closest('section') as SectionElement | null
      if (!section) return

      unregisterItem(el, section)
    },
  })

  // 페이지 이동 시 정리
  if (import.meta.client) {
    nuxtApp.hook('page:finish', () => {
      const currentSections = new Set<SectionElement>(
        Array.from(document.querySelectorAll('section')) as SectionElement[]
      )

      for (const [section, observer] of sectionObservers.entries()) {
        if (!currentSections.has(section)) {
          observer.disconnect()
          sectionObservers.delete(section)
          sectionItems.delete(section)
        }
      }
    })
  }
})