roohollah419 / roullete

Roulette Game API Challenge

Task description

Create an application using NestJS which would serve as the backend side of a simplified version of an online Roulette game.

Goal of the task

An online casino game can not be written entirely on the front-end side. It needs to receive the essential game data(such as winning number in a roulette game or the dealt cards' values in a card game) from a secure source(API), so the player is unable to change the outcome by modifying the source code of the front-end side of the game. We usually develop the whole functional API for the games first, which allow us to test out the whole sequence of the game logic just by interacting with the API and then we start working on the UI part of the game, in which we make use of the data received from the API.

Roulette game rules

1. A standard Roulette table game which has 37 possible winning numbers: 0-36 (0 included).
2. 3 types of bets - Number bet(0-36), Odd bet(1,3,5,7...), Even bet(2,4,6,8...). We don't need other types of bets like Black bet, Red bet and Horizontal bet, to keep it simple.
3. Number bet should have 36/1 winning coefficient, Odd - 2/1, even - 2/1

Example Roulette Game

What the Application should do

I. The application should have 3 endpoints - "create", "spin", "end"

POST create - should receive the player's starting balance and store it in the session.

What this endpoint should do:

1. Initialize a new game session in the session storage of the API(You can use express-session and Redis to setup the session storage for the application).

2. Receive the gameMode property in the request body with 2 possible values:

   • "normal"
   • "testing"

   and store it in the session

3. Receive the player's starting balance:

   • As part of a JWT hashed token(token should be hashed by the secret that needs to be kept in the .env file of the application ) if the gameMode is "normal"
   • As part of the request body if the gameMode is "testing"

4. Store the received balance in the session

   • Verify and decrypt the token in case the game mode is "normal". If the verification is successful, take out the balance and store it, If not Throw an HTTP Exception error with a message letting the user know why the request was not successful.
   • Just store the balance value from the request body to the session in case the game mode is "testing".

PATCH spin - should receive "bets" property with a value equaling array of objects containing 2 properties: betAmount and betType(number, "odd", "even"). The player can place as many bets as he wants. He can place a bet on each number and also make the Odd and Even bets. It should also receive an optional "winningNumber" property in case the game mode is "testing".

example { betInfo:[{betAmount:10, betType:25}, {betAmount:50, betType:0}, {betAmount:50, betType:"even"}, {betAmount:10, betType:"odd"}] }

What this endpoint should do:

1. Check that the player's balance is enough for making every bet. If not, return an error.

2. Determine the win sum(if any)

   • If the "gameMode" property value stored in the session is "normal", Generate a random winning number and and determine the win sum.
   • If the "gameMode" property value is "testing" and the body contains the "winningNumber" property, determine the win sum based on the received "winningNumber", else proceed with the "normal" game mode flow(generating a random winning number).

3. Update the balance in the session and return this balance to the front-end alongside the information about bets which won (for example, {betAmount:10, betType:25} and {betAmount:10, betType:"odd"} could win together if the winning number is 25).

DELETE end - send the information about starting and ending balances to the user(if the user had 1000 balance during "create" and after 10 spins he has 900, response should be {startBalance:1000, endBalance:900} ). It should delete the session as well.

II. All endpoints should validate the request ORIGIN to be some specified value (localhost:3000 in our case)

III. All properties part of the request(balance, winningNumber, gameMode) should be validated using class-validator library. winningNumber and balance(in the body) should only be validated if the game mode is "testing" and they should be strictly undefined in case the gameMode is "normal". gameMode should be validated in both cases("normal" and "testing"). The balance stored in JWT should be validated as well, in case the gameMode is "normal".

Necessary resources

NestJs Official Documentation

NestJs Tutorial

Instructions

1. Create a new Repository on your account
2. Clone this Repository
3. Finish the task
4. Set your new Repository as the origin: git remote set-url origin ${your repo url}
5. Push your local solution to your remote Repository.