perf(island): ⚡ switch to websocket to check connection status changes

islands/IsOnline.tsx

@@ -1,52 +1,41 @@
-import { type Signal, useSignal } from '@preact/signals'
+import { type Signal, useComputed, useSignal } from '@preact/signals'
 import { useEffect } from 'preact/hooks'
-import { JSX } from 'preact'
-import { requestApi } from ':src/utils.ts'
-
-type NetworkConnection = {
-	addEventListener: (
-		type: 'change',
-		listener: (event: Event) => void | Promise<void>,
-	) => void
-}
+import { IS_BROWSER } from '$fresh/runtime.ts'
 
 export default function IsOnline(
 	{ online, offline }: { online?: string; offline: string },
 ) {
-	const status = useSignal(online)
-	const connection = 'connection' in navigator
-		? navigator.connection as NetworkConnection
-		: null
+	if (!IS_BROWSER) {
+		return <span class={'island__is_online'}>{offline}</span>
+	}
 
-	useEffect(() => {
-		// Update connection status on network changes
-		connection?.addEventListener('change', () => {
-			updateNetworkStatus(status, online, offline)
+	const status = useSignal(false)
+	const displayed = useComputed(() => {
+		if (status.value && online) {
+			return <span>{online}</span>
+		}
+		if (status.value) {
+			return <span style={{ display: 'none' }}></span>
+		}
+		return <span class={'island__is_online'}>{offline}</span>
 	})
-		// Update connection status on 1st load
-		updateNetworkStatus(status, online, offline)
-		// Update connection status on interval (10s)
-		setInterval(() => updateNetworkStatus(status, online, offline), 10_000)
+	useEffect(() => openSocket(status, { id: undefined }), [])
+
+	return <>{displayed}</>
+}
+
+function openSocket(status: Signal<boolean>, ref: { id: number | undefined }) {
+	const socket = new WebSocket(
+		`wss://${location.host}/api/serviceworker/is-online`,
+	)
+	socket.addEventListener('open', () => {
+		status.value = true
+		clearInterval(ref.id)
+	})
+	socket.addEventListener('close', () => {
+		status.value = false
+		// Try reconnect every 5s
+		const id = setInterval(() => openSocket(status, ref), 5_000)
+		ref.id = id
 	})
-
-	return <>{status}</>
-}
-
-async function updateNetworkStatus(
-	status: Signal<JSX.Element>,
-	online: string | undefined,
-	offline: string,
-) {
-	const isOnline = await requestApi<void, boolean>(
-		'/serviceworker/is-online',
-		'POST',
-	).catch(() => false)
-
-	if (isOnline) {
-		status.value = online === undefined
-			? <span style={{ display: 'none' }}></span>
-			: <span>{online}</span>
-	} else {
-		status.value = <span class={'island__is_online'}>{offline}</span>
-	}
 }

routes/_middleware.ts

@@ -13,6 +13,10 @@ export async function handler(request: Request, ctx: FreshContext) {
 	// Get response
 	const response = await ctx.next()
 
+	if (ctx.state?.skipMiddlewares) {
+		return response
+	}
+
 	// Use custom middleware hooks
 	useSecurityHeaders(request, response, ctx)
 	await useCsp(request, response, ctx)

routes/api/serviceworker/is-online.tsx

@@ -1,9 +1,9 @@
 import { SessionHandlers } from ':src/session/mod.ts'
-import { respondApi } from ':src/utils.ts'
 
 export const handler: SessionHandlers = {
-	POST() {
-		// Check if server is online
-		return respondApi<'success', true>('success', true)
+	GET(req: Request, ctx) {
+		const { response } = Deno.upgradeWebSocket(req)
+		ctx.state.skipMiddlewares = true
+		return response
 	},
 }