import { useMediaQuery } from '@vueuse/core'
import type { DefaultTheme } from 'vitepress/theme'
import {
  type ComputedRef,
  type Ref,
  computed,
  onMounted,
  onUnmounted,
  ref,
  watch,
  watchEffect,
  watchPostEffect,
} from 'vue'
import { useData } from 'vitepress'

export interface SidebarControl {
  collapsed: Ref<boolean>
  collapsible: ComputedRef<boolean>
  isLink: ComputedRef<boolean>
  isActiveLink: Ref<boolean>
  hasActiveLink: ComputedRef<boolean>
  hasChildren: ComputedRef<boolean>
  toggle: () => void
}

export interface SidebarItem extends DefaultTheme.SidebarItem {}

export function useSidebar() {
  const { frontmatter, theme } = useData()
  const is960 = useMediaQuery('(min-width: 960px)')

  const isOpen = ref(false)

  const hasSidebar = computed(() => {
    return (
      frontmatter.value.sidebar !== false
      && frontmatter.value.layout !== 'home'
    )
  })

  const hasAside = computed(() => {
    if (frontmatter.value.layout === 'home')
      return false
    if (frontmatter.value.aside != null)
      return !!frontmatter.value.aside
    return theme.value.aside !== false
  })

  const isSidebarEnabled = computed(() => hasSidebar.value && is960.value)

  function open() {
    isOpen.value = true
  }

  function close() {
    isOpen.value = false
  }

  function toggle() {
    isOpen.value ? close() : open()
  }

  return {
    isOpen,

    hasSidebar,
    hasAside,
    isSidebarEnabled,
    open,
    close,
    toggle,
  }
}

/**
 * a11y: cache the element that opened the Sidebar (the menu button) then
 * focus that button again when Menu is closed with Escape key.
 */
export function useCloseSidebarOnEscape(
  isOpen: Ref<boolean>,
  close: () => void,
) {
  let triggerElement: HTMLButtonElement | undefined

  watchEffect(() => {
    triggerElement = isOpen.value
      ? (document.activeElement as HTMLButtonElement)
      : undefined
  })

  onMounted(() => {
    window.addEventListener('keyup', onEscape)
  })

  onUnmounted(() => {
    window.removeEventListener('keyup', onEscape)
  })

  function onEscape(e: KeyboardEvent) {
    if (e.key === 'Escape' && isOpen.value) {
      close()
      triggerElement?.focus()
    }
  }
}

export function useSidebarControl(
  item: ComputedRef<DefaultTheme.SidebarItem>,
): SidebarControl {
  const { page, hash } = useData()

  const collapsed = ref(false)

  const collapsible = computed(() => {
    return item.value.collapsed != null
  })

  const isLink = computed(() => {
    return !!item.value.link
  })

  const isActiveLink = ref(false)
  const updateIsActiveLink = () => {
    isActiveLink.value = isActive(page.value.relativePath, item.value.link)
  }

  watch([page, item, hash], updateIsActiveLink)
  onMounted(updateIsActiveLink)

  const hasActiveLink = computed(() => {
    if (isActiveLink.value) {
      return true
    }

    return item.value.items
      ? containsActiveLink(page.value.relativePath, item.value.items)
      : false
  })

  const hasChildren = computed(() => {
    return !!(item.value.items && item.value.items.length)
  })

  watchEffect(() => {
    collapsed.value = !!(collapsible.value && item.value.collapsed)
  })

  watchPostEffect(() => {
    ;(isActiveLink.value || hasActiveLink.value) && (collapsed.value = false)
  })

  function toggle() {
    if (collapsible.value) {
      collapsed.value = !collapsed.value
    }
  }

  return {
    collapsed,
    collapsible,
    isLink,
    isActiveLink,
    hasActiveLink,
    hasChildren,
    toggle,
  }
}

// From https://github.com/vuejs/vitepress/blob/97f9469b6d4eb7ba9de9a1111986581d1f704ec3/src/shared/shared.ts
const inBrowser = typeof document !== 'undefined'

const HASH_RE = /#.*$/
const HASH_OR_QUERY_RE = /[?#].*$/
const INDEX_OR_EXT_RE = /(?:(^|\/)index)?\.(?:md|html)$/

export function isActive(
  currentPath: string,
  matchPath?: string,
  asRegex: boolean = false,
): boolean {
  if (matchPath === undefined) {
    return false
  }

  currentPath = normalize(`/${currentPath}`)

  if (asRegex) {
    return new RegExp(matchPath).test(currentPath)
  }

  if (normalize(matchPath) !== currentPath) {
    return false
  }

  const hashMatch = matchPath.match(HASH_RE)

  if (hashMatch) {
    return (inBrowser ? location.hash : '') === hashMatch[0]
  }

  return true
}

function normalize(path: string): string {
  return decodeURI(path)
    .replace(HASH_OR_QUERY_RE, '')
    .replace(INDEX_OR_EXT_RE, '$1')
}

// From https://github.com/vuejs/vitepress/blob/97f9469b6d4eb7ba9de9a1111986581d1f704ec3/src/client/theme-default/support/sidebar.ts
function containsActiveLink(
  path: string,
  items: any | any[],
): boolean {
  if (Array.isArray(items)) {
    return items.some(item => containsActiveLink(path, item))
  }

  return isActive(path, items.link)
    ? true
    : items.items
      ? containsActiveLink(path, items.items)
      : false
}

// From https://github.com/vuejs/vitepress/blob/fa81e89643523170047ca2c9a690f4d7adf4ffdc/src/client/theme-default/support/sidebar.ts
export interface SidebarLink {
  text: string
  link: string
  docFooterText?: string
}

function ensureStartingSlash(path: string): string {
  return /^\//.test(path) ? path : `/${path}`
}

/**
 * Get the `Sidebar` from sidebar option. This method will ensure to get correct
 * sidebar config from `MultiSideBarConfig` with various path combinations such
 * as matching `guide/` and `/guide/`. If no matching config was found, it will
 * return empty array.
 */
export function getSidebar(
  _sidebar: DefaultTheme.Sidebar | undefined,
  path: string,
): SidebarItem[] {
  if (Array.isArray(_sidebar))
    return addBase(_sidebar)
  if (_sidebar == null)
    return []

  path = ensureStartingSlash(path)

  const dir = Object.keys(_sidebar)
    .sort((a, b) => {
      return b.split('/').length - a.split('/').length
    })
    .find((dir) => {
      // make sure the multi sidebar key starts with slash too
      return path.startsWith(ensureStartingSlash(dir))
    })

  const sidebar = dir ? _sidebar[dir] : []
  return Array.isArray(sidebar)
    ? addBase(sidebar)
    : addBase(sidebar.items, sidebar.base)
}

/**
 * Get or generate sidebar group from the given sidebar items.
 */
export function getSidebarGroups(sidebar: SidebarItem[]): SidebarItem[] {
  const groups: SidebarItem[] = []

  let lastGroupIndex: number = 0

  for (const index in sidebar) {
    const item = sidebar[index]

    if (item.items) {
      lastGroupIndex = groups.push(item)
      continue
    }

    if (!groups[lastGroupIndex]) {
      groups.push({ items: [] })
    }

    groups[lastGroupIndex]!.items!.push(item)
  }

  return groups
}

export function getFlatSideBarLinks(sidebar: SidebarItem[]): SidebarLink[] {
  const links: SidebarLink[] = []

  function recursivelyExtractLinks(items: SidebarItem[]) {
    for (const item of items) {
      if (item.text && item.link) {
        links.push({
          text: item.text,
          link: item.link,
          docFooterText: item.docFooterText,
        })
      }

      if (item.items) {
        recursivelyExtractLinks(item.items)
      }
    }
  }

  recursivelyExtractLinks(sidebar)

  return links
}

/**
 * Check if the given sidebar item contains any active link.
 */
export function hasActiveLink(
  path: string,
  items: SidebarItem | SidebarItem[],
): boolean {
  if (Array.isArray(items)) {
    return items.some(item => hasActiveLink(path, item))
  }

  return isActive(path, items.link)
    ? true
    : items.items
      ? hasActiveLink(path, items.items)
      : false
}

function addBase(items: SidebarItem[], _base?: string): SidebarItem[] {
  return [...items].map((_item) => {
    const item = { ..._item }
    const base = item.base || _base
    if (base && item.link)
      item.link = base + item.link
    if (item.items)
      item.items = addBase(item.items, base)
    return item
  })
}