test.ts

test.ts

/**
 * Here we have type definitions and resolvers for a GraphQL schema. Also shown is the type for the context object passed
 * to each resolver (other types have been omitted for brevity). Each resolver has one issue with it that will cause
 * GraphQL to return an error if that field is requested. In a few sentences, explain what is wrong with each resolver
 * and what you would change to fix it.
 */

interface Context {
  db: DB;
  rest: Rest;
}

interface DB {
  getCommentsByPostId: (id: string) => Promise<Comment[]>;
  getPosts: () => Promise<Post[]>;
  getUsers: () => Promise<User[]>;
  getUserById: (id: string) => Promise<User>;
}

interface User {
  id: string;
  firstName: string;
  lastName: string;
}

interface Post {
  id: string;
  title: string;
  body: string;
}

interface Comment {
  id: string;
  body: string;
}

interface Rest {
  getPayments: (
    cb: (error: Error | null, payments: Payment[]) => void
  ) => void;
}

interface Payment {
  id: string;
  amount: number;
}

const typeDefs = `
  type Query {
    payments: [Payment!]!
    posts: [Post!]!
    user(id: ID!): User
    users: [User!]!
  }

  type Payment {
    id: ID!
    amount: Float!
  }

  type Post {
    id: ID!
    title: String!
    body: String!
    comments: [Comment!]!
  }

  type Comment {
    id: ID!
    body: String!
  }

  type User {
    id: ID!
    fullName: String!
  }
`;

const resolvers = {
  Query: {
    payments: (_root, _args, ctx) => {
      return ctx.rest.getPayments((error, payments) => {
        return payments;
      });
    },
    posts: async (_root, _args, ctx) => {
      return ctx.db.getPosts().then((posts) => {
        return Promise.all(
          posts.map((post) => {
            post.comments = ctx.db.getCommentsByPostId(post.id);
          })
        );
      });
    },
    users: async (_args, ctx) => {
      return ctx.db.getUsers();
    },
    user: (_root, args, ctx) => {
      return ctx.db.getUserById(args.id).then((user) => {
        return user;
      });
    },
  },
};