If you are on Linux, install docker for Linux:

• https://docker.github.io/engine/installation/

If you are on MacOS, install Docker-Compose, VirtualBox, docker-machine and NFS.

• brew install docker-compose
• https://www.virtualbox.org/wiki/Downloads
• https://docs.docker.com/machine/install-machine/
• Run docker-machine create default --driver virtualbox --virtualbox-memory "3072", to create a VM.
• Run eval $(docker-machine env)
• Install NFS https://github.com/adlogix/docker-machine-nfs

1. Give execute permissions to the start script: chmod +x script/start.sh (from the project's root)
2. Run docker-compose build
3. Once the project is built, run docker-compose up
4. Once it finishes compiling and bringing the app up, you should be able to access the app on:

• Run: docker-machine ip
• You should be able to access the app by routing to the docker-machine ip printed from the command above. For example, http://192.168.99.100:4000.
• Or you might have already mapped this locally to localhost or dev. For example, http://localhost:4000 or http://dev:4000.

You will need to have all these dependencies installed (You may want to follow the installation guide on https://hexdocs.pm/phoenix/installation.html):

• Elixir installed
• Mix installed
• Phoenix Framework
• Postgres

Once you have installed it, you should:

1. Give permission to the script to execute chmod +x script/start.sh.
2. Run the script ./script/start.sh

When you run docker-compose up or ./script/start.sh a script on /priv/repo/seeds.exs will run and initially populate the database.

The solution proposed to the exercise is to create a checking_accounts table. That is associated with a transactions table, this table persists the operations made by the credit and debit operations.

Creates a credit transaction to the users account

POST /api/v1/checking_account/:checking_account_id/credit/:amount

• checking_account_id (Integer) - Users account id
• amount (Float) - Amount to credit
• description (string) - Description of transaction
• date (UTC Timestamp) - Amount to credit

• 200
• 404
• 400

POST /api/v1/checking_account/1/credit/100.0?description=payment+from+jow&date=1503704316

{
  "data": "success"
}

Creates a debit (negative amount) transaction to the users account.

POST /api/v1/checking_account/:checking_account_id/debit/:amount

• checking_account_id (Integer) - Users account id
• amount (Float) - Amount to credit
• description (string) - Description of transaction
• date (UTC Timestamp) - Amount to credit

• 200
• 404
• 400

POST /api/v1/checking_account/1/credit/100.0?description=buy+book&date=1503704316

{
  "data": "success"
}

Returns the sum of amount over all transactions created for this user

GET /api/v1/checking_account/:checking_account_id/balance

• checking_account_id (Integer) - Users account id

• 200
• 404

GET /api/v1/checking_account/1/balance

{
  "data": {
    "balance": 123.0
  }
}

Returns the bank statement regarding the given checking account. Given optional start and end date. If start_date and end_date are not given, statement for all transactions will return.

GET /api/v1/checking_account/:checking_account_id/statement

• checking_account_id (Integer) - Users account id
• start_date (UTC Timestamp or YYYY-MM-DD) - start date of the statement
• end_date (UTC Timestamp or YYYY-MM-DD) - end date of the statement

• 200
• 404
• 400

GET /api/v1/checking_account/1/statement

{
  "data": [
    {
      "balance": 123.0,
      "date": "2017-08-25",
      "transactions": [
        {
          "description": "a description",
          "amount" : "1204",
          "ts" : 1234556
        },
        {
          "description": "Another description",
          "amount" : "-14.0",
          "ts" : 1234523
        }
      ]
    }
  ]
}

Returns all the periods in which the given user was on debt.

GET /api/v1/checking_account/:checking_account_id/periods_of_debt

• checking_account_id (Integer) - Users account id

• 200
• 404

GET /api/v1/checking_account/1/periods_of_debt

{
  "data": [
    {
      "start": "2017-08-01",
      "end": "2017-08-04",
      "principal" : "120.0"
    },
    {
      "start": "2017-08-20",
      "end": null,
      "principal" : "120.0"
    }
  ]
}