graphql-server.ts

import { ApolloServer } from '@apollo/server';
import { startStandaloneServer } from '@apollo/server/standalone';
import books from './books.json';
import { BooksDataSource } from './books-data-source.js';

interface ContextValue {
  dataSources: {
    grpcBooks: BooksDataSource;
  };
}

// A schema is a collection of type definitions (hence "typeDefs")
// that together define the "shape" of queries that are executed against
// your data.
const typeDefs = `#graphql
  # Comments in GraphQL strings (such as this one) start with the hash (#) symbol.

  # This "Book" type defines the queryable fields for every book in our data source.
  type Book {
    title: String
    author: String
  }

  # The "Query" type is special: it lists all of the available queries that
  # clients can execute, along with the return type for each. In this
  # case, the "books" query returns an array of zero or more Books (defined above).
  type Query {
    books: [Book],
    grpcBooks: [Book]
  }
`;

// Resolvers define how to fetch the types defined in your schema.
// This resolver retrieves books from the "books" array above.
const resolvers = {
  Query: {
    books: () => books,
    grpcBooks: async (_, __, { dataSources }) => {
      return await dataSources.grpcBooks.getBooks();
    },
  },
};

// The ApolloServer constructor requires two parameters: your schema
// definition and your set of resolvers.
const server = new ApolloServer<ContextValue>({
  typeDefs,
  resolvers,
});

// Passing an ApolloServer instance to the `startStandaloneServer` function:
//  1. creates an Express app
//  2. installs your ApolloServer instance as middleware
//  3. prepares your app to handle incoming requests
startStandaloneServer(server, {
  context: async () => ({
    listen: { port: 4000 },
    dataSources: {
      grpcBooks: new BooksDataSource(),
    },
  })
}).then(({ url }) => {
  console.log(`🚀  Server ready at: ${url}`);
});