serverWEBSCOKETNOTES.md

import express from "express"; import cors from "cors"; import { on } from "events"; import http from "http"; import { server as WebSocketServer } from "websocket";

const app = express(); const port = process.env.PORT || 3000;

app.use(cors());

const server = http.createServer(app); const webSocketServer = new WebSocketServer({ httpServer: server });

const messages = [ { id: 1, username: "annonymous", msgText: "First chat message", timestamp: Date.now(), }, ];

const getRecentMessages = (since) => { return messages.filter((msg) => msg.timestamp > since); };

app.get("/", (req, res) => { res.json(messages); });

//get recent messages polling app.get("/messages", (req, res) => { //This is the problem: // sincetimestapm Teach your backend how to answer “since when” queries. const since = parseInt(req.query.since); if (since) { res.json(getRecentMessages(since)); return; } res.json(messages); });

//messages with long polling const callbacksForNewMessages = []; app.get("/long-poll", (req, res) => { const since = parseInt(req.query.since); let messagesToSend = [];

if (since) {
	messagesToSend = getRecentMessages(since);
}

if (messagesToSend.length === 0) {
	callbacksForNewMessages.push((value) => res.send(value));
} else {
	res.send(messagesToSend);
}

});

//add msg to chat app.post("/", (req, res) => { const bodyBytes = []; req.on("data", (chunk) => bodyBytes.push(...chunk)); req.on("end", () => { const bodyString = String.fromCharCode(...bodyBytes); let body; try { body = JSON.parse(bodyString); } catch (error) { console.error(Failed to parse body ${bodyString} as JSON: ${error}); res.status(400).send("Expected body to be JSON."); return; } if ( typeof body != "object" || !("username" in body) || !("msgText" in body) ) { console.error( Failed to extract username and message text from body: ${bodyString} ); res .status(400) .send( "Expected body to be a JSON object containing keys username and message text." ); return; }

	body.msgText = body.msgText.trim().replace(/[^a-zA-Z0-9,.;:?! ]/g, "");
	body.username = body.username.trim().replace(/[^a-zA-Z0-9,.;:?! ]/g, "");

	if (!body.msgText || !body.username) {
		res.status(400).send("Please add a quote and an username.");
		return;
	}

	if (body.msgText.length > 400 || body.username.length >= 40) {
		res
			.status(400)
			.send(
				"Message text must be up to 400 chars and username must be less than 40 chars."
			);
		return;
	}

	const newId = messages.length + 1;

	const newMessage = {
		id: newId,
		msgText: body.msgText,
		username: body.username,
		timestamp: Date.now(),
	};

	messages.push(newMessage);

	while (callbacksForNewMessages.length > 0) {
		const callback = callbacksForNewMessages.pop();
		callback([newMessage]);
	}

	res.send("ok");
});

});

app.listen(port, () => { console.error(Chat server listening on port ${port}); });

websocket.addEventListener("open", () => { log("CONNECTED"); pingInterval = setInterval(() => { log(SENT: ping: ${counter}); websocket.send("ping"); }, 1000); });

websocket.addEventListener("message", (e) => { log(RECEIVED: ${e.data}: ${counter}); counter++; });

websocket.addEventListener("message", (e) => { const message = JSON.parse(e.data); log(RECEIVED: ${message.iteration}: ${message.content}); counter++; });

websocket.addEventListener("close", () => { log("DISCONNECTED"); clearInterval(pingInterval); });