src/lib/mongodb.ts


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import mongoose from "mongoose";

const MONGODB_URI = process.env.MONGODB_URI;

interface MongooseCache {
  conn: typeof mongoose | null;
  promise: Promise<typeof mongoose> | null;
}

declare global {
  var mongoose: MongooseCache | undefined;
}

let cached = global.mongoose;

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

async function dbConnect() {
  if (!MONGODB_URI) {
    throw new Error("Please define the MONGODB_URI environment variable inside .env.local");
  }

  if (cached!.conn) return cached!.conn;

  if (!cached!.promise) {
    const opts = { bufferCommands: false };
    cached!.promise = mongoose.connect(MONGODB_URI, opts).then((mongoose) => {
      return mongoose;
    });
  }
  
  try {
    cached!.conn = await cached!.promise;
  } catch (e) {
    cached!.promise = null;
    throw e;
  }
  
  return cached!.conn;
}

export default dbConnect;