index.js

const express = require("express");
const dotenvFlow = require("dotenv-flow");
const cors = require("cors");
const cookieParser = require("cookie-parser");
const dns = require("node:dns");

// dotenv-flow is used to manage environment variables across different environments
dotenvFlow.config();

const app = express();

const REACT_APP_URL = process.env.REACT_APP_URL;
const REACT_LOCAL_URL = process.env.REACT_LOCAL_URL;
const PORT = process.env.PORT || 5000;
const isProduction = process.env.NODE_ENV === "production";

if (!isProduction) {
  // Override DNS servers to use Google's public DNS for better reliability in development
  dns.setServers(["8.8.8.8", "8.8.4.4"]);
}

// CORS is configured to allow requests from the frontend url
// and to allow credentials (cookies) to be sent with requests
app.use(
  cors({
    origin: isProduction ? REACT_APP_URL : REACT_LOCAL_URL,
    credentials: true,
    methods: ["GET", "POST", "PUT", "DELETE", "OPTIONS"],
    allowedHeaders: ["Content-Type", "Authorization"],
  })
);

// allow us to parse cookies from the request, this is needed for session management
app.use(cookieParser());

// app will serve and receive data in a JSON format
app.use(express.json());

// trust first proxy for secure cookies in production
if (isProduction) {
  app.set("trust proxy", 1);
}

// Handle routes for authentication and builds
const appRouter = require("./routes");
const { connectToMongoDB } = require("./database/connection");
const { baseRoot } = require("./controllers/authController");

// Await connection before handling any request
app.use(async (req, res, next) => {
  try {
    await connectToMongoDB();
    next();
  } catch (err) {
    console.error("DB unavailable:", err.message);
    return res.status(503).json({ errorMessage: "Database unavailable, try again" });
  }
});

app.get("/", baseRoot);
app.use("/api", appRouter);

// Only start the HTTP server if this file was run directly with `node index.js`
if (require.main === module) {
  app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));
}

module.exports = app;