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import { useEffect, useRef, useState } from 'react'
import { createPortal } from 'react-dom'
import type { FlightRouterState } from '../../server/app-render/types'
const ANNOUNCER_TYPE = 'next-route-announcer'
const ANNOUNCER_ID = '__next-route-announcer__'
function getAnnouncerNode() {
const existingAnnouncer = document.getElementsByName(ANNOUNCER_TYPE)[0]
if (existingAnnouncer?.shadowRoot?.childNodes[0]) {
return existingAnnouncer.shadowRoot.childNodes[0] as HTMLElement
} else {
const container = document.createElement(ANNOUNCER_TYPE)
container.style.cssText = 'position:absolute'
const announcer = document.createElement('div')
announcer.ariaLive = 'assertive'
announcer.id = ANNOUNCER_ID
announcer.role = 'alert'
announcer.style.cssText =
'position:absolute;border:0;height:1px;margin:-1px;padding:0;width:1px;clip:rect(0 0 0 0);overflow:hidden;white-space:nowrap;word-wrap:normal'
// Use shadow DOM here to avoid any potential CSS bleed
const shadow = container.attachShadow({ mode: 'open' })
shadow.appendChild(announcer)
document.body.appendChild(container)
return announcer
}
}
export function AppRouterAnnouncer({ tree }: { tree: FlightRouterState }) {
const [portalNode, setPortalNode] = useState<HTMLElement | null>(null)
useEffect(() => {
const announcer = getAnnouncerNode()
setPortalNode(announcer)
return () => {
const container = document.getElementsByTagName(ANNOUNCER_TYPE)[0]
if (container?.isConnected) {
document.body.removeChild(container)
}
}
}, [])
const [routeAnnouncement, setRouteAnnouncement] = useState('')
const previousTitle = useRef<string | undefined>(undefined)
useEffect(() => {
let currentTitle = ''
if (document.title) {
currentTitle = document.title
} else {
const pageHeader = document.querySelector('h1')
if (pageHeader) {
currentTitle = pageHeader.innerText || pageHeader.textContent || ''
}
}
// Only announce the title change, but not for the first load because screen
// readers do that automatically.
if (
previousTitle.current !== undefined &&
previousTitle.current !== currentTitle
) {
setRouteAnnouncement(currentTitle)
}
previousTitle.current = currentTitle
}, [tree])
return portalNode ? createPortal(routeAnnouncement, portalNode) : null
}
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