Implement proof of concept push notifications

app/api/unsubscribe/route.ts

@@ -0,0 +1,26 @@
+import { readFile, writeFile } from "fs/promises";
+
+export async function POST(request: Request) {
+	const body: { subscription: PushSubscriptionJSON } = await request.json();
+	let subscriptions: PushSubscriptionJSON[];
+	try {
+		subscriptions = JSON.parse(await readFile("push-subscriptions.json", "utf-8"));
+	} catch (err: any) {
+		if (err.code !== "ENOENT") {
+			throw err;
+		}
+		subscriptions = [];
+	}
+	const existingIndex = subscriptions.findIndex(sub => sub.endpoint === body.subscription.endpoint);
+	if (existingIndex !== -1) {
+		subscriptions.splice(existingIndex, 1);
+	} else {
+		return new Response(JSON.stringify({ message: "No subscription registered."}));
+	}
+	await writeFile(
+		"push-subscriptions.json",
+		JSON.stringify(subscriptions, undefined, "\t"),
+		"utf-8"
+	);
+	return new Response(JSON.stringify({ message: "Existing subscription removed."}));
+}