import { MongoClient, Db } from 'mongodb';

const mongoConfig = {
  autoCreate: process.env.NODE_ENV !== 'production',
  readPreference: 'secondaryPreferred',
  connectTimeoutMS: 8000,
  serverSelectionTimeoutMS: 8000,
};

export default class MongoDb {
  private static instance: MongoDb;

  protected client?: MongoClient;

  public static getInstance(): MongoDb {
    if (!MongoDb.instance) {
      MongoDb.instance = new MongoDb();
    }
    return MongoDb.instance;
  }

  private async getMongoClient(): Promise<MongoClient> {
    if (!this.client) {
      const mongoUrl = process.env.DATABASE_URI!;
      this.client = new MongoClient(mongoUrl, {
        connectTimeoutMS: mongoConfig.connectTimeoutMS,
      });
      await this.client.connect();
    }
    return this.client;
  }

  async getDbConnection(): Promise<Db> {
    const client: MongoClient = await this.getMongoClient();
    return client.db();
  }

  async disconnectMongoClient(): Promise<void> {
    const client = await this.getMongoClient();
    await client.close();
    this.client = undefined;
  }
}