We have released an online computer game with some success. We log all played game results of each player.

Our players have requested a ranking by country that they would like to integrate in other systems. We think that is a good idea and that feature will increase our gamers engagement, one of our key metrics.

For that new feature we only want to return the best 10 players for each of our 3 top countries where we have a lot of players: Spain, France and United Kingdom.

We don't want to couple with the legacy system because it's done using an obsolete language/framework with a security issue.

We know that exist something called Anticorruption Layer, that allows us to decouple our new model from the old one.

We would like to model our new business model with Players and Rankings.

DashboardAction is the service class that will be consumed from the API Rest.

RankingRepository will be used by DashboardAction to retrieve the users from the Anticurruption Layer.

In our new model we want to use an ISO Standard for the country id's: ISO_3166-2

We want the return an output as string in JSON format.

{
  "ES":[
    {"id":11,"name":"playerNameA","score":34},
    {"id":20,"name":"playerNameB","score":32},
    {"id":14,"name":"playerNameC","score":30}
  ],
  "FR":[
    {"id":174,"name":"playerNameX","score":43},
    {"id":167,"name":"playerNameY","score":42},
    {"id":155,"name":"playerNameZ","score":40}
  ],
  "GB":[
    {"id":202,"name":"playerNameR","score":38},
    {"id":253,"name":"playerNameS","score":36},
    {"id":288,"name":"playerNameT","score":35}
  ]
}

You need docker to

docker run --name ranking-kata-database -v "$PWD:/home/" -e MYSQL_ROOT_PASSWORD=ranking -p 3306:3306 -d mariadb

docker exec -it ranking-kata-database sh -c "mysql -u root -pranking < /home/legacy_db_script.sql"

The mysql connection information is:

• host: localhost
• port: 3306
• database name: last_survival
• password: ranking

• Understand how to decouple a legacy system from a new one.
• The importance of a good model and frontiers.

Luis Rovirosa @luisrovirosa

Jordi Anguela @jordianguela