import { MongoClient } from "mongodb"

const { MONGODB_URI, MONGODB_DB, MONGODB_COLLECTION } = process.env

let cached = global.mongo

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

export default async function connectToDatabase() {
  if (cached.conn) {
    return cached.conn
  }

  if (!cached.promise) {
    const opts = {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    }

    cached.promise = await MongoClient.connect(MONGODB_URI, opts).then(client => {
      return {
        client,
        coll: client.db(MONGODB_DB).collection(MONGODB_COLLECTION),
      }
    })
  }
  cached.conn = await cached.promise

  return cached.conn
}