API test
We ask that you complete the following challenge to evaluate your development skills. Please use the programming language and framework discussed during your interview to accomplish the following task.
Develop the classic game of Minesweeper
- Create a Public repository ( please dont make a pull request, clone the private repository and create a new plublic one on your profile)
- Commit each step of your process so we can follow your thought process.
The following is a list of items (prioritized from most important to least important) we wish to see:
- Design and implement a documented RESTful API for the game (think of a mobile app for your API)
- Implement an API client library for the API designed above. Ideally, in a different language, of your preference, to the one used for the API
- When a cell with no adjacent mines is revealed, all adjacent squares will be revealed (and repeat)
- Ability to 'flag' a cell with a question mark or red flag
- Detect when game is over
- Persistence
- Time tracking
- Ability to start a new game and preserve/resume the old ones
- Ability to select the game parameters: number of rows, columns, and mines
- Ability to support multiple users/accounts
- URL where the game can be accessed and played (use any platform of your preference: heroku.com, aws.amazon.com, etc)
- Code in a public Github repo
- README file with the decisions taken and important notes
You do not need to fully complete the challenge. We suggest not to spend more than 5 hours total, which can be done over the course of 2 days. Please make commits as often as possible so we can see the time you spent and please do not make one commit. We will evaluate the code and time spent.
What we want to see is how well you handle yourself given the time you spend on the problem, how you think, and how you prioritize when time is insufficient to solve everything.
Please email your solution as soon as you have completed the challenge or the time is up.
First things first, I had to think about the problem. As usual, I started doing some research. I even played minesweeper for quite a while (love the game). I came upon some minesweepers APIs but really did not like any previous implementation I found. Or maybe liked something but did not like other things about it.
I figured the first thing I had to decide was "What are my resources?" The API should be able to access the game, the board and the cells. I was quite a while thinking if only using board and modifying it's state or add cells as resources of the board and just modify cells. Using cells would allow me to have less data payload each time I visit a cell, but client library should have to keep state of all cells.
However, for my first iteration I decided for the following model:
/games
id: unique identifier for a game
board: link to associated board
width: number of cols the board has
height: number of cells the board has
mines: number of total mines
remainingMines: number of remaining mines to uncover
status: game state (won, lost, in progress)
Possible Actions:
POST: Create new game
GET: {id} Get a game's information
GET: Get collection of games -- Not priority initially
/games/{id}/board
id: unique identifier for a game
width: number of cols the board has
height: number of cells the board has
mines: number of total mines
remainingMines: number of remaining mines to uncover
cells: collection of board cells
Possible Actions:
GET: Get the boards's information
_/games/{id}/board/cells_
id: unique identifier for a cell
x: row
y: col
mine: true/false (has mine?)
adjacentMines: number of adjacent mines
flag: true/false (has been flagged as mine)
Possible Actions:
GET: Collection of cells
GET: {x,y} Get the cell information
PUT: {x,y} Visit cell. Changes flag status or returns error is cell had mine
I also thought about what I had to do when creating a game:
- Generate board with random location of mines
- Complete cell information with number of adjacent mines
I decided before exposing any route with resources I'd first implement modules with the needed functionality and test them. Then I would expose whatever I needed.
Whenever I begin a new project, the first thing I do is get a docker up and running. Then, I move forward. So... here I go.
With dockerized dummy app ready, next step is generation of basic functionality with TDD approach. What do I need to do? I need to be able to:
- Create a new game
- Create a board for the game --> generate all cells with random mine location and calculate number of adjacent mines for each cell
- Modify cell --> uncover cell or add mine flag with corresponding status update of board and game
- Get list of games
Once first iteration of Minesweeper Core functionality was ready, I then expose basic API endpoints.
I prioritized first Item in list: building API, trying to ignore extra features as list of games, persistence, etc. Some of the additional features (configure board size and mines, detecting when game ends) were a very natural extension to what I had already built and came with nearly no extra cost.
docker-compose up
Access API on localhost:3000
With docker
docker exec -it minesweeper-api_api_1 sh -c "npm run test"
Inside container or locally
npm run test
https://dry-hamlet-26176.herokuapp.com
Postman collection available in docs folder to test all endpoints and play
Create a new game by POST to /games.
With no body default 9x9 and 10 mines will be created.
Sending JSON body with width, height and mines will create custom board.
Created game will show game status and complete board with no revealed cells.
With the game ID you can then choose to visit a cell or flag a cell.
As long as the server is not restarted you'll be able to play the last game you created.
Visit a cell by GET to /games/:gameId/board/cells/:coords.
gameId is the uuid you obtained when creating a game
coords has the array format [x,y] of the cell you wish to visit
If you enter a cell out of the board, you'll get an error but will be able to continue playing.
If the cell you visit has a mine you'll loose the game. Status will change to Lost and you won't be able to continue playing. Your only option will be to start a new game.
If the cell you visit does not have a mine, you'll reveal the adjacentMines property of the cell which indicates the number of mines surrounding the cell. Status will change to Playing if it hand't yet changed. You'll always be able to see complete board information to continue playing
Flag a cell by PUT to /games/:gameId/board/cells/:coords/flag.
gameId is the uuid you obtained when creating a game
coords has the array format [x,y] of the cell you wish to visit
If you enter a cell out of the board, you'll get an error but will be able to continue playing.
Flagging toggles the flag on a cell. A cell with no flag will be flagged and a cell with a flag will be unflagged.
When you flag a cell, the remainingMines property will be updated.
Every time you flag or visit a cell, the game will check to see if the board is complete. A board is complete if there are no remaining mines to be flagged and if all non mine cells have been visited.
Once you win a game, status will be updated to Won and you won't be able to continue playing. Your only option will be to start a new game.