import type { AdminLayoutMenuItem } from '@/components/layouts/main-layout/types'
import { computed, onBeforeUnmount, onMounted, ref, type Ref, watch } from 'vue'

type ToggleSidebarPayload = {
  drawer: boolean
  rail: boolean
}

type UseAdminLayoutStateOptions = {
  appBarRef: Ref<unknown>
  breadcrumbBarVisible: Ref<boolean | null>
  emitUpdateBreadcrumbBarVisible: (value: boolean) => void
  emitUpdateFavoritesBarVisible: (value: boolean) => void
  emitUpdateIsRail: (value: boolean) => void
  favoritesBarVisible: Ref<boolean | null>
  isMobile: Ref<boolean>
  isRail: Ref<boolean | null> // 必須為 Ref，確保父層 prop 更新時 getter 能即時反映
  menuItems: AdminLayoutMenuItem[]
  onToggleSidebar: (payload: ToggleSidebarPayload) => void
}

export function useAdminLayoutState(options: UseAdminLayoutStateOptions) {
  const drawer = ref(true)
  const mobileFavoritesPanel = ref(false)
  const mobileMenuPath = ref<AdminLayoutMenuItem[]>([])
  const localBreadcrumbBarVisible = ref(true)
  const localFavoritesBarVisible = ref(true)
  const localIsRail = ref(false)
  const opened = ref<string[]>([])
  const appBarHeight = ref(0)

  const isRail = computed({
    get: () => options.isRail.value ?? localIsRail.value,
    set: (value: boolean) => {
      if (options.isRail.value === null) {
        localIsRail.value = value
        return
      }

      options.emitUpdateIsRail(value)
    },
  })

  const showFavoritesBar = computed({
    get: () => options.favoritesBarVisible.value ?? localFavoritesBarVisible.value,
    set: (value: boolean) => {
      if (options.favoritesBarVisible.value === null) {
        localFavoritesBarVisible.value = value
        return
      }

      options.emitUpdateFavoritesBarVisible(value)
    },
  })

  const breadcrumbBarVisible = computed({
    get: () => options.breadcrumbBarVisible.value ?? localBreadcrumbBarVisible.value,
    set: (value: boolean) => {
      if (options.breadcrumbBarVisible.value === null) {
        localBreadcrumbBarVisible.value = value
        return
      }

      options.emitUpdateBreadcrumbBarVisible(value)
    },
  })

  const mobileCurrentItems = computed(() =>
    mobileMenuPath.value.reduce(
      (items, currentItem) => currentItem?.subItems ?? [],
      options.menuItems || []
    )
  )

  const mobileCurrentLevel = computed(() => mobileMenuPath.value.length + 1)

  const mobileMenuLevels = computed(() =>
    Array.from({ length: mobileCurrentLevel.value }, (_, index) => ({
      level: index + 1,
      title:
        index === 0 ? '主選單' : (mobileMenuPath.value[index - 1]?.title ?? `第${index + 1}層`),
    }))
  )

  function resetMobilePanels() {
    mobileFavoritesPanel.value = false
    mobileMenuPath.value = []
  }

  function toggleSidebar() {
    if (options.isMobile.value) {
      drawer.value = !drawer.value
    } else {
      isRail.value = !isRail.value
    }

    options.onToggleSidebar({
      drawer: drawer.value,
      rail: isRail.value,
    })
  }

  function goToMobileLevel(level: number) {
    mobileFavoritesPanel.value = false
    mobileMenuPath.value = mobileMenuPath.value.slice(0, Math.max(0, level - 1))
  }

  function openMobileFavoritesPanel() {
    mobileMenuPath.value = []
    mobileFavoritesPanel.value = true
  }

  function handleMobileMenuClick(
    item: AdminLayoutMenuItem,
    onSelect: (selectedItem: AdminLayoutMenuItem) => void
  ) {
    if (item?.subItems?.length) {
      mobileMenuPath.value = [...mobileMenuPath.value, item]
      return
    }

    onSelect(item)
  }

  function handleSelectFavorite(
    item: AdminLayoutMenuItem,
    onSelect: (selectedItem: AdminLayoutMenuItem) => void
  ) {
    onSelect(item)
    mobileFavoritesPanel.value = false
  }

  function toggleFavoritesBar(nextValue?: boolean) {
    showFavoritesBar.value = typeof nextValue === 'boolean' ? nextValue : !showFavoritesBar.value
  }

  function handleUnshrink() {
    isRail.value = false
  }

  let appBarObserver: ResizeObserver | null = null

  function resolveObservedElement() {
    const target = options.appBarRef.value as HTMLElement | { $el?: HTMLElement } | null
    if (!target) return null
    if (target instanceof HTMLElement) return target
    return target.$el ?? null
  }

  function updateAppBarHeight() {
    const el = resolveObservedElement()
    if (!el) return
    appBarHeight.value = Math.round(el.getBoundingClientRect().height || 0)
  }

  onMounted(() => {
    updateAppBarHeight()
    if (typeof ResizeObserver === 'undefined') return

    const el = resolveObservedElement()
    if (!el) return

    appBarObserver = new ResizeObserver(() => updateAppBarHeight())
    appBarObserver.observe(el)
  })

  onBeforeUnmount(() => {
    if (!appBarObserver) return
    appBarObserver.disconnect()
    appBarObserver = null
  })

  watch(options.isMobile, (value) => {
    if (!value) {
      resetMobilePanels()
    }
  })

  watch(drawer, (value) => {
    if (!value) {
      resetMobilePanels()
    }
  })

  const mainStyle = computed(() => ({
    paddingTop: appBarHeight.value ? `${appBarHeight.value}px` : undefined,
    height: '100vh',
    minHeight: 0,
    flex: '1 1 0',
  }))

  return {
    drawer,
    goToMobileLevel,
    handleMobileMenuClick,
    handleSelectFavorite,
    handleUnshrink,
    isRail,
    mainStyle,
    mobileCurrentItems,
    mobileCurrentLevel,
    mobileFavoritesPanel,
    mobileMenuLevels,
    openMobileFavoritesPanel,
    opened,
    breadcrumbBarVisible,
    showFavoritesBar,
    toggleFavoritesBar,
    toggleSidebar,
  }
}