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[existingIndex] = body.subscription;
	} else {
		subscriptions.push(body.subscription);
	}
	await writeFile(
		"push-subscriptions.json",
		JSON.stringify(subscriptions, undefined, "\t"),
		"utf-8"
	);
	if (existingIndex !== -1) {
		return new Response(JSON.stringify({ message: "Existing subscription refreshed."}));
	}
	return new Response(JSON.stringify({ message: "New subscription registered."}));
}