import { Schedule } from "~/shared/types/schedule"

function sendMessage(
	stream: WritableStream<string>,
	message: string,
) {
	const writer = stream.getWriter();
	writer.ready
		.then(() => writer.write(message))
		.catch(console.error)
		.finally(() => writer.releaseLock())
	;
}

const streams = new Set<WritableStream<string>>();

let keepaliveInterval: ReturnType<typeof setInterval> | null = null
export function addStream(stream: WritableStream<string>) {
	if (streams.size === 0) {
		console.log("Starting keepalive")
		keepaliveInterval = setInterval(sendKeepalive, 4000)
	}
	streams.add(stream);
}
export function deleteStream(stream: WritableStream<string>) {
	streams.delete(stream);
	if (streams.size === 0) {
		console.log("Ending keepalive")
		clearInterval(keepaliveInterval!);
	}
}

export function broadcastUpdate(schedule: Schedule) {
	const id = Date.now();
	const data = JSON.stringify(schedule);
	const message = `id: ${id}\nevent: update\ndata: ${data}\n\n`
	console.log(`broadcasting update from ${process.pid} to ${streams.size} clients`);
	for (const stream of streams) {
		sendMessage(stream, message);
	}
}

function sendKeepalive() {
	for (const stream of streams) {
		sendMessage(stream, "data: keepalive\n\n");
	}
}