import express from 'express';
import { WebSocketServer } from 'ws';
import http from 'node:http';
import serveIndex from 'serve-index';
import Busboy from 'busboy';


const app = express();
const server = http.createServer(app);
const wss = new WebSocketServer({ noServer: true });


// resource -> Set<WebSocket>
const subscriptions = new Map();

function subscribe(ws, resource) {
	if (!subscriptions.has(resource)) {
		subscriptions.set(resource, new Set());
	}
	subscriptions.get(resource).add(ws);
	ws._subscriptions ??= new Set();
	ws._subscriptions.add(resource);
}

function unsubscribeAll(ws) {
	if (!ws._subscriptions) return;
	for (const resource of ws._subscriptions) {
		subscriptions.get(resource)?.delete(ws);
	}
}

// WebSocket upgrade
server.on('upgrade', (req, socket, head) => {
	if (req.url !== '/subscription') {
		socket.destroy();
		return;
	}

	wss.handleUpgrade(req, socket, head, ws => {
		wss.emit('connection', ws, req);
	});
});

wss.on('connection', ws => {
	ws.on('message', msg => {
		let data;
		try {
			data = JSON.parse(msg.toString());
		} catch {
			return;
		}

		if (data.cmd === 'subscribe' && typeof data.resource === 'string') {
			subscribe(ws, data.resource);
		}
	});

	ws.on('close', () => {
		unsubscribeAll(ws);
	});
});

// Emit endpoint

app.post('/emit/:resource', (req, res) => {
	const { resource } = req.params;
	const chunks = [];

	req.on('data', chunk => chunks.push(chunk));
	req.on('end', () => {
		const payload = Buffer.concat(chunks);
		res.status(204).end();

		const subs = subscriptions.get(resource);
		if (subs) {
			for (const ws of subs) {
				try {
					ws.send(payload);
					console.log('[emit] sent to subscriber');
				} catch (err) {
					console.log('[emit] send failed, removing subscriber:', err?.message);
					subs.delete(ws);
				}
			}
		}

	});
});


app.post('/emit-multipart', (req, res) => {
	const bb = Busboy({ headers: req.headers });

	let resource = null;
	const chunks = [];

	bb.on('field', (name, value) => {
		if (name === 'resource') {
			resource = value;
		}
	});

	bb.on('file', (name, file) => {
		file.on('data', chunk => chunks.push(chunk));
	});

	bb.on('close', () => {
		if (!resource) {
			res.status(400).end('missing resource');
			return;
		}

		const payload = Buffer.concat(chunks);
		res.status(204).end();

		const subs = subscriptions.get(resource);
		if (subs) {
			for (const ws of subs) {
				try {
					ws.send(payload);
					console.log('[emit-multipart] sent to subscriber');
				} catch (err) {
					console.log('[emit-multipart] send failed, removing subscriber:', err?.message);
					subs.delete(ws);
				}
			}
		}
	});

	req.pipe(bb);
});


app.use('/', express.static('static'), serveIndex('static', { icons: true }));


server.listen(3888);