user.ts

import { buildFederatedSchema } from '@apollo/federation';
import { ApolloServer, gql } from 'apollo-server';
import User from './datasources/models/User';
import mongoStore from './mongoStore';

const typeDefs = gql`
  type User @key(fields: "id") {
    id: ID!
    username: String!
  }
  extend type Query {
    users: [User]
    user(id: ID!): User
  }
  extend type Mutation {
    createUser(userPayload: UserPayload): User
  }
  input UserPayload {
    username: String!
  }
`;

const resolvers = {
  Query: {
    users: async () => {
      const allUsers = await User.find({});
      return allUsers;
    },
    user: async (_, { id }) => {
      const currentUser = await User.findOne({ _id: id });
      return currentUser;
    },
  },
  User: {
    __resolveReference: async (ref) => {
      const currentUser = await User.findOne({ _id: ref.id });
      return currentUser;
    },
  },
  Mutation: {
    createUser: async (_, { userPayload: { username } }) => {
      const user = new User({ username });
      const createdUser = await user.save();
      return createdUser;
    },
  },
};

mongoStore();

const server = new ApolloServer({
  schema: buildFederatedSchema([{ typeDefs, resolvers }]),
});

server.listen({ port: 4001 }).then(({ url }) => {
  console.log(`User service ready at url: ${url}`);
});