This is the index.js to be used when the database is incorporated

index.js

const { ApolloServer, gql } = require("apollo-server");
const { MongoClient, ObjectID } = require("mongodb");

const typeDefs = gql`
    type Photo {
        id: ID!
        name: String!
        description: String
        category: PhotoCategory!
        url: String
        postedBy: User!
    }

    type User {
        githubLogin: ID!
        name: String!
        postedPhotos: [Photo!]!
    }

    enum PhotoCategory {
        PORTRAIT
        LANDSCAPE
        ACTION
        SELFIE
    }

    input PostPhotoInput {
        name: String!
        description: String
        category: PhotoCategory=PORTRAIT
    }

    type Query {
        totalPhotos: Int!
        allPhotos: [Photo!]!
        Photo(id: ID!): Photo!
        totalUsers: Int!
        allUsers: [User!]!
        User(githubLogin: ID!): User
    }

    type Mutation {
        postPhoto(input: PostPhotoInput!): Photo!
    }
`;

const resolvers = {
  Query: {
    totalPhotos: (parent, args, { photos }) => photos.countDocuments(),
    allPhotos: (parent, args, { photos }) => photos.find().toArray(),
    Photo: (parent, { id }, { photos }) =>
      photos.findOne({ _id: ObjectID(id) }),
    totalUsers: (parent, args, { users }) => users.countDocuments(),
    allUsers: (parent, args, { users }) => users.find().toArray(),
    User: (parent, { githubLogin }, { users }) => users.findOne({ githubLogin })
  },
  Mutation: {
    postPhoto: async (parent, { input }, { photos, currentUser }) => {
      if (!currentUser) {
        throw new Error("only an authorized user can post a photo");
      }

      const newPhoto = {
        ...input,
        userID: currentUser.githubLogin
      };

      const { insertedId } = await photos.insertOne(newPhoto);
      newPhoto.id = insertedId.toString();
      console.log(newPhoto);
      return newPhoto;
    }
  },
  Photo: {
    id: parent => parent.id || parent._id.toString(),
    url: parent => `/img/photos/${parent.id || parent._id.toString()}.jpg`,
    postedBy: (parent, args, { users }) =>
      users.findOne({ githubLogin: parent.userID })
  },
  User: {
    postedPhotos: (parent, args, { photos }) =>
      photos.find({ userID: parent.githubLogin }).toArray()
  }
};

const start = async () => {
  const client = await MongoClient.connect(
    process.env.DB_HOST,
    { useNewUrlParser: true }
  );
  const db = client.db();

  const server = new ApolloServer({
    typeDefs,
    resolvers,
    context: {
      photos: db.collection("photos"),
      users: db.collection("users"),
      currentUser: null
    }
  });

  server
    .listen()
    .then(({ port }) => `server listening on ${port}`)
    .then(console.log)
    .catch(console.error);
};

start();