import { nextTick, type App, type Directive, type DirectiveBinding } from 'vue'
import router from '@/router'

import { pinia, usePermissionStore } from '@/store'
import type { PermissionDirectiveValue } from '@/types/permission'

type PermissionHTMLElement = HTMLElement & {
	__permissionDisplay?: string
	__permissionDividerDisplay?: string
	__permissionLabel?: string
	__permissionTextNode?: Text
	__permissionObserver?: MutationObserver
	__permissionLabelConfig?: {
		menuCode: string
		buttonCode: string
		label?: string
		usePermissionName?: boolean
	}
}

const resolveVisibilityElement = (el: PermissionHTMLElement) =>
	(el.closest('.el-dropdown-menu__item') as PermissionHTMLElement | null) || el

const resolveDropdownDivider = (el: PermissionHTMLElement) => {
	const visibilityElement = resolveVisibilityElement(el)
	const previousElement = visibilityElement.previousElementSibling as PermissionHTMLElement | null

	return previousElement?.getAttribute('role') === 'separator' ? previousElement : undefined
}

const updateVisibility = (el: PermissionHTMLElement, visible: boolean) => {
	const visibilityElement = resolveVisibilityElement(el)
	const dropdownDivider = resolveDropdownDivider(el)

	if (visibilityElement.__permissionDisplay === undefined) {
		visibilityElement.__permissionDisplay = visibilityElement.style.display
	}
	if (dropdownDivider && dropdownDivider.__permissionDividerDisplay === undefined) {
		dropdownDivider.__permissionDividerDisplay = dropdownDivider.style.display
	}

	visibilityElement.style.display = visible ? visibilityElement.__permissionDisplay || '' : 'none'

	if (dropdownDivider) {
		dropdownDivider.style.display = visible
			? dropdownDivider.__permissionDividerDisplay || ''
			: 'none'
	}
}

// 支持三种写法：v-permission="'add'"、v-permission="['menu', 'add']"、对象形式。
const resolvePermissionBinding = (binding: DirectiveBinding<PermissionDirectiveValue>) => {
	const currentMenuCode =
		typeof router.currentRoute.value.meta.menuCode === 'string'
			? router.currentRoute.value.meta.menuCode
			: undefined

	if (typeof binding.value === 'string') {
		return {
			menuCode: currentMenuCode,
			buttonCode: binding.value
		}
	}

	if (Array.isArray(binding.value)) {
		return {
			menuCode: binding.value[0],
			buttonCode: binding.value[1]
		}
	}

	return {
		menuCode: binding.value?.menuCode || currentMenuCode,
		buttonCode: binding.value?.buttonCode,
		label: binding.value?.label,
		usePermissionName: binding.value?.usePermissionName
	}
}

const resolveTextNode = (el: PermissionHTMLElement) => {
	if (el.__permissionTextNode && el.contains(el.__permissionTextNode)) {
		return el.__permissionTextNode
	}

	const walker = document.createTreeWalker(el, NodeFilter.SHOW_TEXT)
	let node = walker.nextNode()

	while (node) {
		if (node.textContent?.trim()) {
			el.__permissionTextNode = node as Text
			return el.__permissionTextNode
		}
		node = walker.nextNode()
	}

	return undefined
}

const updateButtonLabel = (
	el: PermissionHTMLElement,
	menuCode: string,
	buttonCode: string,
	label?: string,
	usePermissionName?: boolean
) => {
	const permissionStore = usePermissionStore(pinia)
	const shouldUsePermissionName = usePermissionName ?? label === undefined
	const resolvedLabel = shouldUsePermissionName
		? permissionStore.getButtonPermissionName(menuCode, buttonCode, label || buttonCode)
		: label || buttonCode

	const textNode = resolveTextNode(el)
	if (!textNode) return

	if (el.__permissionLabel === resolvedLabel && textNode.textContent === resolvedLabel) return

	// 只替换按钮的首个文本节点，保留前置图标和其他插槽内容不变。
	textNode.textContent = resolvedLabel
	el.__permissionLabel = resolvedLabel
}

const ensureButtonLabelObserver = (el: PermissionHTMLElement) => {
	if (el.__permissionObserver) return

	el.__permissionObserver = new MutationObserver(() => {
		const config = el.__permissionLabelConfig
		if (!config) return

		updateButtonLabel(
			el,
			config.menuCode,
			config.buttonCode,
			config.label,
			config.usePermissionName
		)
	})

	el.__permissionObserver.observe(el, {
		childList: true,
		characterData: true,
		subtree: true
	})
}

const scheduleButtonLabelUpdate = async (
	el: PermissionHTMLElement,
	menuCode: string,
	buttonCode: string,
	label?: string,
	usePermissionName?: boolean
) => {
	el.__permissionLabelConfig = { menuCode, buttonCode, label, usePermissionName }
	ensureButtonLabelObserver(el)

	updateButtonLabel(el, menuCode, buttonCode, label, usePermissionName)
	await nextTick()
	updateButtonLabel(el, menuCode, buttonCode, label, usePermissionName)
	requestAnimationFrame(() => {
		updateButtonLabel(el, menuCode, buttonCode, label, usePermissionName)
	})
}

const updatePermissionVisibility = async (
	el: PermissionHTMLElement,
	binding: DirectiveBinding<PermissionDirectiveValue>
) => {
	const { menuCode, buttonCode, label, usePermissionName } = resolvePermissionBinding(binding)
	if (!menuCode || !buttonCode) {
		updateVisibility(el, false)
		return
	}

	const permissionStore = usePermissionStore(pinia)
	await permissionStore.ensureButtonPermissions(menuCode)

	const allowed = permissionStore.hasButtonAccess(menuCode, buttonCode)
	// 自定义指令只负责隐藏无权限按钮，不改变按钮原有业务逻辑。
	updateVisibility(el, allowed)

	if (allowed) {
		void scheduleButtonLabelUpdate(el, menuCode, buttonCode, label, usePermissionName)
	}
}

const permissionDirective: Directive<PermissionHTMLElement, PermissionDirectiveValue> = {
	mounted(el, binding) {
		void updatePermissionVisibility(el, binding)
	},
	updated(el, binding) {
		void updatePermissionVisibility(el, binding)
	},
	unmounted(el) {
		el.__permissionObserver?.disconnect()
	}
}

export const installPermissionDirective = (app: App) => {
	app.directive('permission', permissionDirective)
}