twitter-kata

Run and build

##docker:

Prerequisites

- docker-compose

Run

docker-compose -f app/docker-compose.yml up

##local:

Prerequisites

- java >= 8
- sbt 1.5.8
- dynamodb (can be used from docker-compose)
- [temporal] add in /etc/hosts 
    `0.0.0.0 dynamodb-local`

Run

sbt run

Description

The goal of this kata is to practice Clean Architecture driven by Outside-in TDD.

You will build a basic Twitter application following a set of restrictions on each iteration. Try to apply DRY, KISS, and SOLID principles during the process.

Restrictions

• Write the best code you can, while keeping it simple.
• Don't do more than the iteration asks.
• Don't add infrastructure if the functionality doesn't explicitly ask for it.
• Don't rely on libraries if the functionality doesn't explicitly ask for it.

Iteration 1

• A user can register with his real name and a nickname. Eg: Jack Bauer, @jack.

• If another person has been already registered using the same nickname an error is expected.

Iteration 2

• The user can update his real name.

Iteration 3

• A user can follow other users. The nickname of the other user is all it needs to follow it.

• Anyone can ask who is following who, just knowing the nickname

⚠️ From this point on, you should not modify the code written in previous iterations ⚠️

Iteration 4

• The records of the users and the followed users must be stored in a durable form. (Discuss with your onboarding buddy about the current technologies in use)

Iteration 5

• Create an HTTP delivery mechanism that allows accessing all the functionalities developed so far. (Discuss with your onboarding buddy about the current technologies in use)

Iteration 6

• A user can tweet. Other users can read all tweets of a user knowing his username.

Design and implementation details

Persistence model

Entities and relationships

User{
    nickname
    realname
}

Follow{
    follower_id
    followee_id
}

users - 0..n -> followees
users - 0..n -> followers

access patterns

User:
    - register user                     = PK=USER#johnbauer1 , SK=USER#johnbauer1
    - update user                       = PK=USER#johnbauer1 , SK=USER#johnbauer1
Follow:
    - follow a user                     = PK=USER#janedoe    , SK=FOLLOWED#johnbauer
    - find all followees from a user    = PK=USER#johnbauer1 , SK=FOLLOWED#
Tweet*:
    - A user can tweet                  = PK=USER#<nickname> , SK=TWEET#<tweet-id>
    - Read tweets from user             = PK=USER#<nickname> , SK=TWEET#

data modeling

Entity	Paritition key (PK)	Sort key (SK)	Attributes
User	USER#<nickname>	USER#<nickname>	realname: String
Followed	USER#<nickname>	FOLLOWED#<nickname>	timestamp: String
Tweet*	USER#<nickname>	TWEET#<tweet-id>	message: String, timestamp: String

Paritition key (PK)	Sort key (SK)	Attributes
USER#johnbauer1	USER#johnbauer1	John Bauer
USER#juliarobers2	USER#juliarobers2	Julia Robers
USER#juliarobers2	FOLLOWED#johnbauer	202204071222
USER#johnbauer1*	TWEET#123abc	Hello twitter!, 202204071322

Presentation model

Register user:

POST /users/
  {
    nickname: string,
    realname: string
  }
  
  returns:
    201: created
    409: user already registered
    500: service error

Update user:

PUT /users/<nickname>
  {
    realname: string
  }
  
  returns:
    204: updated
    404: user not found 
    500: service error

Follow user:

POST /users/<nickname>/follows
  {
    followeeId: string
  }
  
  returns:
    204: ok
    404: user not found 
    500: service error

Who is following who:

GET /users/<nickname>/follows
  {}
  
  returns:
    200: [ {
      - nickname: string,
      - realname: string
    } ]
    404: user not found
    500: service error

Tweet message:

POST /user/<nickname>/tweet
  {
    - message: string
  }
  
  returns:
    201: ok
    404: user not found
    500: service error

Request tweets:

GET /user/<nickname>/tweet

  returns:
    200: ok
      [{
        - id: string
        - message: string
      }]
    404: user not found
    500: service error

To-Do:

• [DONE] Terminar la relacion el modelado de base
• [DONE] Levantar docker
• [DONE] Conectar una cli para tirar comandos (o UI)
• [DONE] Crear tablas en Dynamolocal mediante los tests
• [DONE] Conectar las queries de usuarios y follows con DynamoDB
• [DONE] Test integracion
• [DONE] Implementar capa de presentacion http con http4s
• [DONE] Implementar Tweet feature
• [DONE] CI : Gitlab
• [DONE] Dockerizar

NTH:

• Definir configuracion (ciris?) PURE CONFIG
• Configurar logger de http4s para ver RequestLogs y ResponseLogs
• Configurar healtcheck route que pinguee el estado los appResources
• Unificar Category index para tener las distintas extensiones
• Definir una Query.empty[FooIndex] que solo empiece con FOO# (reemplazar la actual)
• Correr it tests en paralelo

Assumptions

• A user can register any nickname (not just '@' starting)
• A user cannot change its nickname
• Persistence shared across multiple fibers (concurrent)
• Cannot store user list of followers/following in a single item (scalability). i.e following and followed are separated entities in persistence