Challenge 2: Track Connected Clients With Logging — Possible Solution
====================================================================

import { WebSocketServer } from "ws";

const wss = new WebSocketServer({ port: 8080 });
const clients = new Set();

wss.on("connection", (socket) => {
  clients.add(socket);
  console.log(`Client connected. Current count: ${clients.size}`);

  socket.on("message", (data) => {
    socket.send(data.toString()); // echo, as in Challenge 1
  });

  socket.on("close", () => {
    clients.delete(socket);
    console.log(`Client disconnected. Current count: ${clients.size}`);
  });

  socket.on("error", (err) => {
    console.error("Socket error:", err);
  });
});

console.log("Echo server with client tracking listening on port 8080");

WHY THIS WORKS
--------------
- A Set is a natural fit for tracking connected sockets: adding the same
  socket twice is a no-op (Sets only store unique values), and removing
  a specific socket via clients.delete(socket) is a simple, direct
  operation — no need to search through an array for a matching index.
- clients.add(socket) happens INSIDE the "connection" handler, at the
  moment a client's socket object is created — this is the earliest
  point the client can be tracked.
- clients.delete(socket) happens inside THAT SAME socket's "close"
  handler, not some later cleanup pass — this guarantees the client is
  removed from tracking at the exact moment its connection actually
  ends, keeping clients.size always accurate.
- Logging clients.size right after both add() and delete() gives a
  real-time view of how many clients are currently connected, which is
  exactly the kind of visibility a raw ws server doesn't give you for
  free — you have to build it yourself, unlike some higher-level
  libraries that track this automatically (previewed in the next
  chapter).
- This same "clients" Set is the foundation the broadcast pattern in
  Challenge 3 builds directly on top of.