models.js

'use strict'
const mongoose = require('mongoose')

const inDevelopment = process.env.NODE_ENV !== 'production'

// Connect to the local MongoDB database named “testdb”
mongoose.connect(
  inDevelopment ? 'mongodb://localhost/testdb' : process.env.MONGO_URL
)

// Create a Group schema to be stored in the MongoDB database
const GroupSchema = new mongoose.Schema({
  _id: String,
  name: String
})

// Turn that schema into a model that we can query
const Group = mongoose.model('Group', GroupSchema)

// Create a User schema to be stored in the MongoDB database
const UserSchema = new mongoose.Schema({
  _id: String,
  username: String,
  groupId: String
})

// Retrieve the group associated with the user
UserSchema.methods.group = function() {
  // Use .exec() to ensure a true Promise is returned
  return Group.findById(this.groupId).exec()
}

// Turn that schema into a model that we can query
const User = mongoose.model('User', UserSchema)

module.exports = { User, Group }