server.js

const { createServer } = require("node:http");
const { parse } = require("node:url");
const next = require("next");

const dev = process.env.NODE_ENV !== "production";
const hostname = "localhost";
const port = 3000;

const app = next({ dev, hostname, port });
const handle = app.getRequestHandler();

app.prepare().then(() => {
  const handleUpgrade = app.getUpgradeHandler();
  // Import WebSocket server module
  const { initWebSocketServer } = require("./src/lib/websocket-server.ts");

  const server = createServer(async (req, res) => {
    try {
      const parsedUrl = parse(req.url, true);
      await handle(req, res, parsedUrl);
    } catch (err) {
      console.error("Error occurred handling", req.url, err);
      res.statusCode = 500;
      res.end("internal server error");
    }
  });

  // Initialize WebSocket server using the extracted module
  const wss = initWebSocketServer();

  // Handle upgrade requests manually
  // This allows us to route /api/arduino/ws to our WebSocket server
  // while letting Next.js handle /_next/webpack-hmr
  server.on("upgrade", async (request, socket, head) => {
    const { pathname } = parse(request.url);

    if (pathname === "/api/arduino/ws") {
      // Handle our custom WebSocket path
      wss.handleUpgrade(request, socket, head, (ws) => {
        wss.emit("connection", ws, request);
      });
      return;
    }

    if (pathname?.startsWith("/_next/")) {
      try {
        await handleUpgrade(request, socket, head);
      } catch (error) {
        console.error("[Server] Error forwarding Next.js upgrade:", error);
        socket.destroy();
      }
      return;
    }

    // Reject unknown WebSocket paths
    console.log("[Server] Rejecting upgrade for:", pathname);
    socket.destroy();
  });

  server.once("error", (err) => {
    console.error(err);
    process.exit(1);
  });

  server.listen(port, () => {
    console.log(`> Ready on http://${hostname}:${port}`);
    console.log(`> WebSocket ready on ws://${hostname}:${port}/api/arduino/ws`);
  });
});