CODING TEST: PART 1

RUNNING THE APP

To avoid port conflict between my tests and my running demon, the main app runs under 🚀 Server ready at http://localhost:5000/graphql (notice port 5000).

You can run this project with yarn install to install the dependencies and then yarn run start or yarn run demon

Note on authentification

Authentification was supposed to be already effective. Thus, I added in apollo Server configuration a context callback that will automatically log you as "user2". In a real production context, a complete authentification system, using jwt, etc, should be used instead.

Assumptions and choices:

• The term "forums" will be used instead of "fora" because it better matches the list naming convention (adding an "s" at the end)
• Two forums cannot have the same name. This allows forum creation to use names to verify if the forum already exists.
• Since a database wasn't required, I directly load a .json file in the server memory. Data is modified directly by a mutation resolver. The code is thus longer than it would have been with database queries. For example, I have to generate a new ID by hand when a forum is added to the "database".
• SendingTime is computed server-side. This way, we simplify client mutation queries, we simplify time zone handling, we prevent users from sending a message to prior times (thus modifying chat history), and messages are already stored in order.
• I decided to implement a pagination system for messages. I could have gone for an offset system, but cursor-based pagination is now a "best practice" and allows more flexibility. Even though cursors usually are strings, an Int is enough because of the messages data structure.

Extra Packages

Except for linters and prettier, and ts-dev (faster than nodemon), I did not use any extra package

Tests:

I added several tests in the tests folder. They ensure that every requirement of the specs is fulfilled. I'm using jest so you can run yarn run test or npm run test to check that everything is working well.

Github Actions

A .github folder can be found at the root of the project. A yml configuration file inside runs whenever this branch is pushed. Jest action launches the test files. Thus, we can quickly verify that integration is not broken. (CI)

SCHEMA

The following schema is taken from the inspector page available thanks to the apollo server. I provide below the full retrieved schema, but

• directive @cacheControl
• CacheControlScope
• Upload

are not shown here because they were automatically created by apollo. (The SDL file can be found under src/schema/type-defs.ts)

  """
  DateTime custom scalar type compliant with iso 8601
  """
  scalar DateTime

  """
  The schema's root query type
  """
  type Query {
    """
    Retrieve all existing forums
    """
    forums: [Forum]!

    """
    Retrieve forum having a specific ID
    """
    forum(id: ID!): Forum

    """
    Retrieve the current logged User
    """
    me: User
  }

  """
  The schema's root mutation type
  """
  type Mutation {
    """
    Create a new Forum if it doesn't already exist
    """
    createForum(input: createForumInput!): Forum

    """
    Join an existing forum having the given ID
    """
    joinForumByID(input: joinForumByIDInput!): Forum

    """
    Join an existing forum having the given Name
    """
    joinForumByName(input: joinForumByNameInput!): Forum

    """
    create a new message
    """
    createMessage(input: createMessageInput!): Message
  }

  ## Pagination -----------------------

  """
  Page Information to perform cursor-based pagination
  """
  type PageInfo {
    """
    True if a previous page exits
    """
    hasPreviousPage: Boolean!

    """
    True if a next page exists
    """
    hasNextPage: Boolean!

    """
    Cursor of the first node returned
    """
    startCursor: Int!

    """
    Cursor of the last node returned
    """
    endCursor: Int!
  }

  ## FORUM ----------------------------

  """
  A Forum
  """
  type Forum {
    id: ID!
    name: String!
    """
    Members of this Forum
    """
    members: [User]!
    """
    A cursor-based navigation object to paginate over forum messages
    """
    messages(first: Int!, after: Int): MessageConnection
  }

  """
  Required fields to createForum
  """
  input createForumInput {
    forumName: String!
  }

  """
  Required fields to joinForumByID
  """
  input joinForumByIDInput {
    forumID: ID!
  }

  """
  Required fields to joinForumByName
  """
  input joinForumByNameInput {
    forumName: String!
  }

  ## MESSAGE --------------------------

  """
  A message
  """
  type Message {
    text: String!
    sender: User!
    """
    The sending time of this message, computed when the message reaches the server
    """
    sendingTime: String!
  }

  """
  Required fields to createMessage
  """
  input createMessageInput {
    """
    The text content of the message
    """
    text: String!
    """
    The forumId of the forum targeted by this message
    """
    forumID: String!
  }

  """
  A connection object for a cursor-based pagniation over Messages
  """
  type MessageConnection {
    """
    Total number of messages
    """
    totalCount: Int

    """
    Edge for a cursor-based pagination over messages
    """
    edges: [MessageEdge]!

    """
    Info to paginate over received mesages
    """
    pageInfo: PageInfo!
  }

  """
  Edge for a cursor-based pagination over messages
  """
  type MessageEdge {
    """
    The cursor identifying a single message
    """
    cursor: Int!

    """
    Node containing a single Message
    """
    node: Message!
  }

  ## USER -----------------------------
  """
  A user
  """
  type User {
    name: String!
    """
    Avatar
    """
    image: String!
    """
    The list of forums where this user is a member
    """
    forums: [Forum]
  }