Elixir + Phoenix - Checking Account REST API

A REST API that handles operations (credit and debit) in a given checking account.

Operations of an account are organized with a struct containing type, number, description, amount and date.

• type represents types of operations allowed to put (deposit, salary, credits) money and take (withdrawal, purchase, debits) money from the account
• number is the account number
• description is a description of the operations
• amount is value added or taken from the account
• date is the date in which the operation happened

To store all operations of a given account is being used an Agent which represents a bucket where all operations are stored with the following structure where all operations are group by account. That way you can easily see which operations belong to an account and easily retrieve the operations of an account

{
  "123": [operation, operation],
  "456": [operation, operation],
}

There's only one bucket created, it's called operations and store all operations. That buckekt is created through a GenServer that manages all created buckets. If the API had to manage clients, for example, to store clients, you would just need to request the GenServer to create a bucket and pass the name of the new bucket clients. This GenServer is created in the module Bank.Bucket.Registry. The GenServer is supervised by the supervisor created in the module Bank.Bucket.Supervisor.

The operations can be added with the date in any given order and whenever a request is sent to check the balance, get account statement or see if there are periods of debts, the operations are ordered by date before doing any computation on the operations.

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This project is using:

• Elixir - Functional programming language
• Phoenix Framework - An Elixir Web Framework
• Git - Version Control System
• Gitlab - Online Service to host and share Git repositories with the world

To get started you have to have installed on your machine Git and Erlang + Elixir.

Installing Elixir

Follow the instruction to install Elixir on your machine

Cloning the repository

git clone https://gitlab.com/opaulochaves/checking-account-api.git
cd checking-account-api

Getting the dependencies

mix deps.get

Running tests

mix test

There are unit and integration tests. The tests run in parallel.

Starting the server

mix phx.server

The server is available at localhost:4000. I suggest you to test the API using a REST client called Postman.

API

All endpoints accept and return JSON. When making requests to the API you should set a header Accept: application/json.

The API contains four endpoints:

GET /accounts/:number/operations

List all operations of a checking account where account number is :number

Example Request:

GET /accounts/123/operations

{
  "data": [
    {...},
    {...}
  ]
}

POST /accounts/:number/operations

Add an operations to a given account

Example Request:

POST /accounts/123/operations

{
  "operation": {
    "type": "deposit",
    "description": "A deposit",
    "amount": "750",
    "date": "2017-08-10T00:00:00"
  }
}

• type can be deposit, salary, credits, withdrawal, purchase, debts
• amount must be > 0
• date must be <= CURRENT_DATE

Response:

201 Created

{
  "data": {
    "type": "deposit",
    "number": "123",
    "description": "A deposit",
    "amount": 750,
    "date": "2017-08-10T00:00:00"
  }
}

GET /accounts/:number/balance

Get the current balance of a given checking account

Example Request:

GET /accounts/123/balance

{
  "data": {
    "balance": 750
  }
}

GET /accounts/:number/statement/:start_date/:end_date

Get the bank statement of a period of dates. It returns a list where each element is an object containing a date, list of operations of the day, and the balance at the end of the day

Example Request:

GET /accounts/123/statement/2017-08-01/2017-08-10

{
  "data": [
    {
      "operations": [{...}],
      "date": "2017-08-10",
      "balance": 750
    }
  ]

GET /accounts/:number/debts

Get the periods of debts. Returns a list of periods where each element is an object that contains start_date, end_date and debt

Example Request:

GET /accounts/123/debts

{
  "data": [
    {
      "start_date": 9999-01-01,
      "end_date": 9999-12-31,
      "debt": -999
    }
  ]

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Learn more

• Official website: http://www.phoenixframework.org/
• Guides: http://phoenixframework.org/docs/overview
• Docs: https://hexdocs.pm/phoenix
• Mailing list: http://groups.google.com/group/phoenix-talk
• Source: https://github.com/phoenixframework/phoenix