Programming Challenge: Game Server

By: Ben Caine

This is a generic game server used to host arbitrary turn based text games. Games are played through a RESTful interface, with responses and requests sending JSON. Games can be easily added to the server by adding a ruby file to the games/ directory with a play(json) function.

Overview

This game server uses the following technology:

Ruby 2.0.0
Sinatra 1.4.5
DataMapper 1.2.0
SQLite 3.7.13
json (gem) 1.8.1

Installation

Ensure you have Ruby 2.0 installed and bundler.

If you don't have bundler, run gem install bundler

Then you can run bundle install which should install all dependencies.

File Structure

Gemfile - Used by bundle to install gems
dmconfig.rb - Used by DataMapper to set up the SQLite database
game_server.rb - Main file of our service
game_server.db - SQLite database file (may not exist yet)
games/ - Directory of all of our games.
helpers/ - Directory of our helper files
models/ - Our permanent classes
resources/ - Our RESTful interface

Running the service

To run the service, simply type ruby game_server.rb

This should launch a local server you can access at "localhost:4567"

Check that it works by doing curl localhost:4567/ and ensuring it returns "Welcome to Ben's Game Server!"

API / Interface

Users

GET /users/ returns a list of users (in JSON form)
GET /users/:id/ returns a JSON representation of the user (including wins/losses)
POST /users/ creates a new User and returns the id of that user.

Games

GET /games/ returns a list of game types
PUT /games/:token/ takes JSON, plays the game, returns the current state
POST /games/:game_type/user/:user_id/ Starts a game of :game_type for user :user_id. Returns token ID to use in /games/:token/

Adding Games

Adding games is very straight forward. You simply need to create a new file (and class) in the games/ directory that includes "Game", with a property :id, and function play(json) which accepts JSON and returns a response hash.

require './models/game'
class YourGame
	include Game
	property :id, Serial
	property :game_field, Integer, :default => 0
	# More properties here if needed

	def play(json_data)
		# Code here that implements a turn in the game
		response
	end
end

Note: The response must have a :done => true, and a :won => true (or false) when the game is finished (see below)

{
	"won":true,
	"done":true,
	"response":"Some Message",
	"some_data": 0 
}

Then you need to restart the server. On server start, a table will be automatically generated in SQLite and the game will be playable through the game interface.

Playing (Testing)

I provided a simple "game" called guess_number that you can use for testing the API's.

To start, we want to first create a user.

curl -X POST -d '' localhost:4567/users/

{"user_id":2}

We then can test that we can list every user.

curl localhost:4567/users/

["{\"id\":1,\"wins\":0,\"losses\":0,\"total\":0,\"created_at\":\"2014-10-13T20:26:48-04:00\"}"]

We can also test that the /users/:id/ endpoint works.

curl localhost:4567/users/1/

{"id":1,"wins":0,"losses":0,"total":0,"created_at":"2014-10-13T20:26:48-04:00"}

Next, we want to check our game endpoints.

curl localhost:4567/games/

["guess_number","mock"]

We then want to start a game, which we do with a request to /games/:game_type/user/:user_id/ which returns a token number we will use next.

curl -X POST -d '' localhost:4567/games/guess_number/user/1/

{"game_token":1}

We can then use that game token number to play the game through the PUT /games/:token/ endpoint.

curl -X PUT -H "Content-Type: application/json" -d '{"guess": "5"}' localhost:4567/games/1/

{"won":true,"done":true,"response":"Congrats, You won!","tries":1,"chances":10}

That's it for the API, but you can do some sanity checks.

Check that the users score is updated.

curl localhost:4567/users/

["{\"id\":1,\"wins\":1,\"losses\":0,\"total\":1,\"created_at\":\"2014-10-13T22:52:53-04:00\"}"]

Or if you prefer

curl localhost:4567/users/1/

{"id":1,"wins":1,"losses":0,"total":1,"created_at":"2014-10-13T22:52:53-04:00"}

bcaine / gameserver