Player wallet

About

This is a study application with the following technologies:

• node.js
• espress
• typescript
• PostgreSQL

How it works:

• there is no GUI, just API endpoints
• there is a Postman collection of tests in the ./tests directory
• a simple log file is located in ./bin/www/log/
• Basic authentication is used with a hardcoded username and password.

Notes:

• Git: the project is small there are not many commits. To better show how I use Git (Git Flow) I committed all the branches and keept them.
• PostgreSQL: there are two procedures in the project. PostgreSQL 12 was used (the current Stable version).
• There is a more technical documentation in ./documentation/Technical_documentation.md
• Postman: in .env the server is set to run on port 4000, this may be adjusted in Postman's requests.

Setup

1. Create the database

CREATE DATABASE player_wallet
    WITH
    OWNER = postgres
    ENCODING = 'UTF8'
    LC_COLLATE = 'en_US.UTF-8'
    LC_CTYPE = 'en_US.UTF-8'
    CONNECTION LIMIT = -1;

2. Set the environment config file .env with the DB values an Node port.

3. Update the modules: $ npm install.

4. Import the DB schema by running the query from ./initdb.pgsql. (It was ment to be run by $ npm run initdb, but I don't know all the quirks of PostgreSQL yet.)

5. Run the application: $ npm run dev

6. Open Postman and import the collection ./tests/Player wallet.postman_collection.json.

How it works

The main point was to connect all the functionalities into a working example.

All the functionalities are prepared in the test cases in Postman. It's only a matter of going through the and click "Send" on each of them.

Starting point:

There are some preexisting "Players" (records in the player table)

Players' wallets

In the Wallet collection in Postman there are PUT requests that set the value in the players' wallets. For simplicity, since each Player can have only one Wallet, they are both in the same table - a player record has a wallet column - player.wallet_funds. This doesn't get recorded as a transaction in the app.

The funds amount must be a number > 1.

Play session

I think of a play session like a Game. By posting to api/play-session a new session is created with a bet factor.

While the session is "open" a player can place bets.

Betting

While a session is "open", the betAmount can be changed, but not the betFactor. This is done by posting to api/bet. This creates a transaction in the wallet_transaction table.

Winning

By posting to api/win the bet is won. The winning amount is calculated by the formula: winningAmount = betAmount * betFactor.

This event closes the Session (session_satus=won), creates a transaction in the wallet_transaction table and adds the winningAmount to the player.wallet_funds. The three steps are done in the DB with a procedure named play_session_close.

Losing

By posting to api/lose the the bet is marked a lost. The session is closed and no transaction is created, for there are no funds to transfer.

History

To view all the player's data, the transactions and open play sessions, the api/history GET request is used which returns all the mentioned data.

Test case

Run the tests in Postman in the following order (check the port used first, if different than 4000):

1. History / Player 1 - shows Player_1's data with the funds in the wallet set to 0.
2. Wallet / Player 1: funds 12.34 - sets the funds of the player to 12.34.
3. Play session / Player 1: session 1 - create - creates a play session
4. Play session / Player 1: session 2 - create - creates a second play session
5. Bet / Player 1: session 1 - Bet - creates a bet in the session
6. Bet / Player 1: session 2 - Bet - creates a bet in the second session
7. Bet / Player 1: session 1 - Win - sets the bet as won
8. History / Player 1 - shows Player_1's data with the transactions and sessions.

{
    "player": [
        {
            "player_id": 1,
            "player_name": "Aldo",
            "wallet_funds": "8.72",
            "created": "2020-07-08T16:29:42.945Z"
        }
    ],
    "wallet_transactions": [
        {
            "wallet_transaction_id": 1,
            "play_session_id": 1,
            "wallet_funds_before": "12.34",
            "transaction_amount": "2.75",
            "created": "2020-07-08T16:42:44.359Z"
        },
        {
            "wallet_transaction_id": 2,
            "play_session_id": 2,
            "wallet_funds_before": "9.59",
            "transaction_amount": "5.00",
            "created": "2020-07-08T16:42:49.527Z"
        },
        {
            "wallet_transaction_id": 3,
            "play_session_id": 1,
            "wallet_funds_before": "4.59",
            "transaction_amount": "4.13",
            "created": "2020-07-08T16:42:58.563Z"
        }
    ],
    "play_sessions": [
        {
            "play_session_id": 2,
            "play_session_name": "Beta",
            "session_status": "open",
            "bet_amount": "5.00",
            "bet_factor": "2.10",
            "created": "2020-07-08T16:42:24.446Z",
            "last_updated": "2020-07-08T16:42:49.527Z"
        },
        {
            "play_session_id": 1,
            "play_session_name": "Alpha",
            "session_status": "won",
            "bet_amount": "2.75",
            "bet_factor": "1.50",
            "created": "2020-07-08T16:42:20.143Z",
            "last_updated": "2020-07-08T16:42:58.563Z"
        }
    ]
}

Known issues

• The data validation is in place but is not include all possible cases.
• The authentication should be at least read from a config.
• The .env file should not be put in version control, but a sample .env.sample should be.
• The endpoints could be split in separate files.
• There is no handling for invalid requests, to inexistent endpoints or method types.
• The technical documentation is very rudimentary (./documentation/Technical_documentation.md) and not complete.
• The store procedures should use transactions because they are modifying multiple tables.
• The logging is very basic, but it works. A package named Winston could be used to improve that.