monkeytype/backend/init/db.ts

import {
  AuthMechanism,
  Collection,
  Db,
  MongoClient,
  MongoClientOptions,
  WithId,
} from "mongodb";
import MonkeyError from "../utils/error";
import Logger from "../utils/logger";

let mongoClient: MongoClient;
let db: Db;

export async function connect(): Promise<void> {
  const {
    DB_USERNAME,
    DB_PASSWORD,
    DB_AUTH_MECHANISM,
    DB_AUTH_SOURCE,
    DB_URI,
    DB_NAME,
  } = process.env;

  if (!DB_URI || !DB_NAME) {
    throw new Error("No database configuration provided");
  }

  const connectionOptions: MongoClientOptions = {
    connectTimeoutMS: 2000,
    serverSelectionTimeoutMS: 2000,
  };

  if (DB_USERNAME && DB_PASSWORD) {
    connectionOptions.auth = {
      username: DB_USERNAME,
      password: DB_PASSWORD,
    };
  }

  if (DB_AUTH_MECHANISM) {
    connectionOptions.authMechanism = DB_AUTH_MECHANISM as AuthMechanism;
  }

  if (DB_AUTH_SOURCE) {
    connectionOptions.authSource = DB_AUTH_SOURCE;
  }

  mongoClient = new MongoClient(DB_URI, connectionOptions);

  try {
    await mongoClient.connect();
    db = mongoClient.db(DB_NAME);
  } catch (error) {
    Logger.error(error.message);
    Logger.error(
      "Failed to connect to database. Exiting with exit status code 1."
    );
    process.exit(1);
  }
}

export function getDb(): Db | undefined {
  return db;
}

export function collection<T>(collectionName: string): Collection<WithId<T>> {
  if (!db) {
    throw new MonkeyError(500, "Database is not initialized.");
  }

  return db.collection<WithId<T>>(collectionName);
}