dbService.js

var MongoClient = require('mongodb').MongoClient;
const bcrypt = require('bcryptjs');

const url = 'mongodb://localhost:27017/';
let instance = null;

var usersCol;
var sessionsCol;
var db;

try {
    MongoClient
        .connect(url, { 
            useUnifiedTopology: true 
        })
        .then(client => {
            console.log('Connected to Database')
			db = client.db('app-prototype')
			usersCol = db.collection('users')
            sessionsCol = db.collection('sessions')
    });

} catch (error){
    console.log("DB Connect Error:", error);
}

class DbService {
    static getDbServiceInstance(){
        return instance ? instance : new DbService();
    }

    async registerUser(email, passwordHash){
        try {

            //check if user exists
            var check = await usersCol.findOne({"email": email})

            //create new user
            if (check === null){
      
                var user = {
                    "email" : email,
                    "password": passwordHash
                }

                await usersCol.insertOne(user)
                return null;

            //if user already exists
            } else {
                return "User already exists"
            }

        } catch (error) {
            console.log(error);
            return error;
        }
    }

    async registerSession(email, sessionToken){
        try{
            //check if session exists
            var check = await sessionsCol.findOne({"email": email})

            //create new session if first session
            if (check === null){

                var session = {
                    "email": email,
                    "token": sessionToken
                }

                await sessionsCol.insertOne(session)
            

            //otherwise, update session
            } else {
                var newItem = {
                    "token": sessionToken
                }

                await sessionsCol.updateOne({"email": email}, { $set: newItem })
            }
            
        } catch (error) {
            console.log(error);
            return
        }
    }

    async findSession(sessionToken){
        try{
            //check if session exists
            var session = await sessionsCol.findOne({"token": sessionToken})

            //create new session if first session
            if (session === null){
                return null
            } else {
                return session
            }
            
        } catch (error) {
            console.log(error);
            return
        }


    }

    async signIn(email, enteredPassword){
        try {

            //pull user from database
            var user = await usersCol.findOne({"email": email})

            if (user){

                var password = user.password
                console.log(user)
                console.log(user.password)
                const passwordMatches = await bcrypt.compare(enteredPassword, password);
                if (passwordMatches){
                    return null
                } else{
                    return "Incorrect password"
                }

            } else{
                return "Username not found"
            }

        } catch (error) {
            console.log(error);
            return error;
        }
    }


    async addMap(email, lat, long, bbox, points){
        try{
            var newItem = {
                "latitude": lat,
                "longitude": long,
                "bbox": bbox,
                "points": points
            }

            await usersCol.updateOne({"email": email}, { $set: newItem });

        } catch (error){
            console.log(error)
            return error
        }

    }

    async getUser(email){

        try{
            var user = await usersCol.findOne({"email": email})
            return user

        }

        catch (error){
            console.log(error)
            return error
        }
    }

}

module.exports = DbService;