Added new version checker

scripts/NewVersionCheck.ts

@@ -0,0 +1,41 @@
+import { delay } from "./Utils"
+import StatusMessage from "./StatusMessage"
+
+let etags = new Map<string, string>()
+let hasNewVersion = false
+let newVersionCheckDelay = 60000
+
+export async function checkNewVersion(url: string, statusMessage: StatusMessage) {
+	if(hasNewVersion) {
+		return
+	}
+
+	try {
+		let response = await fetch(url)
+
+		if(!response.ok) {
+			console.warn("Error fetch", url)
+			return
+		}
+
+		let newETag = response.headers.get("ETag")
+		let oldETag = etags.get(url)
+
+		if(newETag) {
+			etags.set(url, newETag)
+		}
+
+		if(oldETag && newETag && oldETag !== newETag) {
+			statusMessage.showInfo("A new version of the website is available. Please refresh the page.", -1)
+
+			// Do not check for new versions again.
+			hasNewVersion = true
+			return
+		}
+	} catch(err) {
+		console.warn("Error fetching", url + "\n", err)
+	}
+
+	delay(newVersionCheckDelay).then(() => checkNewVersion(url, statusMessage))
+}
+