mongoose.js

const mongoose = require("mongoose");

const MONGODB_URI = process.env.MONGODB_URI;

if (!MONGODB_URI) {
  throw new Error("MONGODB_URI is not defined in .env");
}

/**
 * Global is used here to maintain a cached connection across hot reloads
 * in development. This prevents connections growing exponentially
 * during API Route usage.
 */
let cached = global.mongo;

if (!cached) {
  cached = global.mongo = { conn: null, promise: null };
}

const connectToDatabase = async () => {
  console.log("Connecting to MongoDB...");

  // Connect to cached connection if available
  if (cached.conn) {
    console.log("Cached MongoDB Connected successfully");
    return cached.conn;
  }

  // Connect to MongoDB
  if (!cached.promise) {
    const opts = {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    };

    cached.promise = mongoose.connect(MONGODB_URI, opts);

    const db = mongoose.connection;
    db.on("error", console.error.bind(console, "connection error: "));
    db.once("open", function () {
      console.log("MongoDB Connected successfully");
    });
  }
  cached.conn = await cached.promise;
  return cached.conn;
};

module.exports = {
  connectToDatabase,
};